Two large clinical trials have shown a reduced rate of breast cancer development in high-risk women in the initial 5 years of follow-up after use of aromatase inhibitors . Here, we report blinded long-term follow-up results for the IBIS-II trial, which compared anastrozole with placebo, with the objective of determining the efficacy of anastrozole for preventing breast cancer  in the post-treatment period.IBIS-II is an international, randomised, double-blind, placebo-controlled trial. Postmenopausal women at increased risk of developing breast cancer were recruited and were randomly assigned (1:1) to either anastrozole  or matching placebo daily for 5 years. After treatment completion, women were followed on a yearly basis to collect data on breast cancer incidence, death, other cancers, and major adverse events (cardiovascular events and fractures). The primary outcome was all breast cancer.vs 165 cases, hazard ratio [HR] 0·51, 95% CI 0·39–0·66, p<0·0001). The reduction was larger in the first 5 years , but still significant after 5 years , and not significantly different from the first 5 years (p=0·087). Invasive oestrogen receptor-positive breast cancer was reduced by 54% , with a continued significant effect in the period after treatment. A 59% reduction in ductal carcinoma in situ was observed , especially in participants known to be oestrogen receptor-positive . No significant difference in deaths was observed overall  or for breast cancer (two anastrozole vs three placebo). A significant decrease in non-breast cancers was observed for anastrozole , owing primarily to non-melanoma skin cancer. No excess of fractures or cardiovascular disease was observed.3864 women were recruited between Feb 2, 2003, and Jan 31, 2012. 1920 women were randomly assigned to 5 years anastrozole and 1944 to placebo. After a median follow-up of 131 months (IQR 105–156), a 49% reduction in breast cancer was observed for anastrozole (85 This analysis has identified a significant continuing reduction in breast cancer with anastrozole in the post-treatment follow-up period, with no evidence of new late side-effects. Further follow-up is needed to assess the effect on breast cancer mortality.Cancer Research UK, the National Health and Medical Research Council Australia, Breast Cancer Research Foundation, Sanofi Aventis, and AstraZeneca. Early work on therapeutic prevention of breast cancer has focused on selective oestrogen receptor modulators (SERMs), such as tamoxifen and raloxifene, which show anti-oestrogenic effects on the breast, as well as agonistic or antagonistic effects on some other organs. In a meta-analysis of several SERMs,3A greater short-term reduction in breast cancer incidence was seen in two trials using, the aromatase inhibitors, anastrozoleThe International Breast Cancer Intervention Study II (IBIS-II) was initiated in 2003 and recruited postmenopausal women without breast cancer but at high risk of developing it to receive either anastrozole (1 mg daily) or matching placebo. The first analysis after a median follow-up of 60 months (IQR 36–85) reported a significant reduction in incidence of 53% for all breast cancer .Evidence before this studyAt the time of the initial publication of this trial, we searched PubMed for reports published in English between Jan 1, 1980, and May 30, 2013. We used the search terms “breast cancer”, “prevention”, and “aromatase inhibitor”. Only one other prevention trial using an aromatase inhibitor had been reported and it has been discussed. However, we identified several adjuvant trials using aromatase inhibitors in which contralateral tumours were reported. We also identified an overview of selective oestrogen receptor modulators for breast cancer prevention. Two large trials in which aromatase inhibitors are being assessed for prevention of ductal carcinoma were also identified. For this Article, we repeated the search up to Oct 30, 2019. A US Preventive Services Task Force review was found, but no new studies on breast cancer prevention with aromatase inhibitors were identified.Added value of this studyWe report results of the randomised IBIS-II trial on the extended duration of benefit of anastrozole in preventing breast cancer up to 12 years after entry and indicate for the first time a long-term benefit, which is larger than that seen for tamoxifen in this period. No excess of fractures, other cancers, cardiovascular disease, or death from any specific cause was seen in the extended follow-up. The number needed to treat to prevent one breast cancer has been reduced to 29.Implications of all the available evidenceOur results provide additional support for the use of anastrozole as the treatment of choice for breast cancer risk reduction in most postmenopausal women at high risk of developing breast cancer. Its use has been supported by the National Institute for Health and Care Excellence in the UK and the US Preventive Services Task Force. Identification of women at high risk of early symptoms of oestrogen depletion and their management remains a challenge.A long-term term reduction of breast cancer incidence for anastrozole or any aromatase inhibitor has not been established, as it has for tamoxifen.IBIS-II is an international, randomised, double-blind, placebo-controlled trial. Detailed study design and inclusion and exclusion criteria have previously been reported.The trial was approved by the UK North West Multi-Centre Research Ethics Committee and was done in accordance with the Declaration of Helsinki (1996 revision), under the principles of good clinical practice. All participants provided written, informed consent to join the study, provide baseline and follow-up blood samples, and have their past and future health records examined, including access to mammograms and pathology material.vs 76·7% placebo, p=0·0053). A further analysis was planned to take place around 5 years after the last report,Consenting eligible women were randomly assigned (1:1) to either anastrozole  or matching placebo daily for 5 years. Randomisation was stratified by country. All participants and medical personnel were blinded to treatment allocation, which was only held by the central study statistician. Unblinding was only permitted if the participant developed breast cancer, when a clinician considered there to be valid medical or safety reasons, or the participant requested unblinding. Treatment allocation still remains largely blinded for investigators and participating women who have not developed breast or any other cancer . In the UK, these events were also collected through cancer registries and National Health Services . In non-UK centres, annual questionnaire or annual clinic visits were used to collect these data.The primary outcome was the development of histologically confirmed breast cancer—either invasive or non-invasive . Secondary outcomes were oestrogen receptor-positive breast cancer, breast cancer mortality, other cancers, cardiovascular disease, fractures, and all-cause mortality. Exploratory analyses reported treatment effects by more detailed breast cancer type, specific baseline patient characteristics , and other major cancers by site.All analyses were done on an intention-to-treat basis, including all randomly assigned patients. Analyses of the efficacy endpoints were based on hazard ratios (HRs) using Cox proportional hazard models,The funder of the study had no role in study design, data collection, data analysis, data interpretation, or writing of the report. The corresponding author had full access to all the data in the study and had final responsibility for the decision to submit for publication.2. Other baseline demographics are shown in the All women randomly assigned to treatment  have been included in this analysis. 3704 (95·9%) were still at risk of developing breast cancer after the 5-year treatment period  and follow-up is ongoing . Median vs 165 placebo [8·5%]; 250 breast cancers have been reported  of the breast cancers were invasive, and 151 (74·4%) of these were reported as oestrogen receptor-positive. A 54% reduction in incidence with anastrozole was observed for oestrogen receptor-positive cancers , with a larger 61% reduction in the first 5 years , and no effect on other specific cancers was apparent . A small non-significant increase in number of events during the active treatment period  was counterbalanced by slight reduction of events after treatment was completed . Myocardial infarctions were evenly distributed between treatment groups (vs eight) or in follow-up after treatment (eight vs six). Numbers of deep vein thromboses were slightly increased in the placebo group, with no differences observed in the two periods .No effect was seen on any other major adverse event . In partt groups , and no  periods . Cases o periods . TransieOther less serious side-effects observed in the first 5 years during treatment with anastrozole,vs 70 placebo; vs two placebo), but numbers are very small. Given the small number of deaths and the relatively young median age at entry (59·4 years), substantially longer follow-up will be needed to determine whether anastrozole affects breast cancer and other cause mortality. Deaths from cancers other than breast did not differ between treatment groups (p=0·39).139 (3·6%) women died during the study (69 anastrozole This updated analysis of the IBIS-II trial provides additional support for the use of anastrozole in breast cancer prevention for high-risk postmenopausal women. The large 61% reduction in breast cancer incidence in the first 5 years has been maintained in subsequent follow-up to 12 years. The significant 36% reduction during post-treatment follow-up was not significantly smaller than during treatment, and still greater than that observed for tamoxifen, which has produced a roughly constant 29% reduction for 20 years.The previously observedAll women have completed the active follow-up period of the trial and now are followed for long-term outcomes by various methods. In the UK, long-term data are collected through national registries for deaths, cancers, and major predefined adverse events, so we are confident that data are complete. Additionally, we still collect data through annual questionnaires where appropriate. For international centres, annual questionnaires were used to collect information on all primary and secondary outcomes. However, data on lesser side-effects, such as hot flushes and musculoskeletal events, were only collected during the 5-year treatment period.In conclusion, these updated results show a continuing long-term effect of 5 years of anastrozole treatment in preventing breast cancer in high-risk postmenopausal women. No new major adverse events were identified. Overall, our data substantially strengthen the findings from our initial report after 5 years of follow-up.j.cuzick@qmul.ac.uk. Details for data sharing policy and application process can be found on the website of Queen Mary University London.Data will be available according to IBIS-II's data sharing plan. Requests for specific analyses or data can be submitted by email to


FOXA1 gene body. FOXA1 is an essential transcription factor for mammary gland development and estrogen responsiveness of breast tissue. Young age at first full-term pregnancy (FFTP) is an important factor in breast cancer risk reduction. It is postulated that this protective effect is the result of stable molecular signatures imprinted by physiological process of pregnancy, but the molecular mechanism of this protective role is unclear. The aim of the current study was to identify the effect of early FFTP on methylation status of FOXA1 gene body methylation. Fresh frozen normal breast tissues (n = 51) were collected from Iranian women who underwent cosmetic mammoplasty (27 nulliparous women and 24 parous women who have experienced first pregnancy before the age of 25). DNA was extracted and then methylated DNA immunoprecipitation (MeDIP) real-time PCR was used to assess FOXA1 methylation level is significantly higher in early parous compared with nulliparous group (p = 0.041). Our results revealed that FOXA1 in normal breast tissue. More investigation is required for clarifying molecular mechanisms underlying this association in order to develop breast cancer prevention strategies.Our study provides new hint about the association between early FFTP and epigenetic modifications within gene body of  This malignancy has various risk factors that are divided into modifiable and non-modifiable factors. An early first full-term pregnancy (FFTP) is the most effective modifiable and natural prevention method against breast cancer that can decrease women’s lifelong risk up to 50%th century. He noted that “the nuns are found with breast tumors more than any other women”, and he deduced this because nuns remain celibate and childless in their lifetime[2].The first documented scrutiny of this preventive performance was conducted by Bernardino Ramazzini, the father of industrial medicine, in 18et al.'s[1] research, in which they carried out an international collaborative case-control study. They found that pregnancy at early age associates with protection against breast cancer. Women who experienced their first pregnancy before 20 years of age had a 50% reduced risk of breast cancer compared with nulliparous women[1]. Postponing first delivery after 35 years of age had a 23% increased breast cancer risk[3]. The early pregnancy protective effect is predominantly against estrogen receptor (ER) positive breast tumors[4] and this protection is negligible for first gestations, which occur between the age of 30 to 34 years. A lot of epidemiological studies have shown that further gestations and breastfeeding increase the mentioned protective effect[7-9]. It is important to consider this protection because most women in different countries, especially in Western communities, have been shown to remain nullipara or to postpone the first pregnancy till the age of 35. Therefore, the recognition of possible molecular mechanisms involved in protective effect of pregnancy will stimulate the advancement of new cancer prevention strategies. Major evidence that displayed a correlation between parity and decreased breast cancer risk was through MacMahon [12-16]. In addition to the complete differentiation of breast tissue, it has been suggested that FFTP protective effect may occur through three ways, including parity-specific changes in the levels of circulating hormones, reduction in the number of mammary stem cells, and variation in response to estrogen in normal breast tissue[4]. Despite extensive studies, the molecular mechanisms of parity-associated protective effect remain unclear. The lifelong breast cancer protection requires persistent molecular changes in the genome of mammary cells; hence, we hypothesize that epigenetic alterations, which are stable and permanent, may play a role in pregnancy-associated protective effect. A previous survey has revealed that the breast epithelial nuclei of postmenopausal parous women are small and heterochromatic with the high level of histone methylation, as compared to nulliparous females[12]. Therefore, since 2014, researchers have focused on the investigation of parity-associated epigenetic alterations in the breast tissue of human and mice. For instance, Ghosh et al.[17] have studied the epigenetic modifications of the normal breast tissue and found some parity-specific hypermethylated and hypo-methylated genes. FOXA1 was an important hypermethylated gene among their findings. Several animal models studies have revealed that physiological process of early FFTP can induce particular molecular signatures in normal breast tissue. Researchers have demonstrated that these molecular changes play an important role in full differentiation of mammary glands and finally result in lifelong breast cancer prevention, also it is critical for the complete function of ERα, which is essential for hormone responsiveness of mammary tissue. It has been shown that FOXA1 co-occupies ERα enhancers in the genome and regulates the expression of ERα downstream target genes. It has also been explained that the lack of FOXA1 expression leads to decreased breast cancer cell proliferation[22].FOXA1 is a pioneer transcription factor for mammary gland development and has a significant function in the biology of luminal epithelial cells of the breast tissue[23]. Since molecular status and molecular interactions in tumor tissues can be modified by malignancy process, which finally result in differences between malignant and normal tissues, in the next step, we evaluated this association in normal breast tissue with a different quantitative methylation assay, methylated DNA immunoprecipitation (MeDIP). According to our results, there was no relation between FFTP and ESR1 methylation levels in normal breast tissue[24]. Therefore, in the current study, we focused on FOXA1 as an upstream regulator of ER function, and the methylation status of FOXA1 gene was investigated in normal breast tissue specimens of early parous and nulliparous women, in order to identify specifically the effect of early parity on gene body methylation of FOXA1.In a preliminary research, we revealed the significant association between ESR1 methylation and some reproductive factors such as FFTP in breast tumorsSamples collection and DNA extraction2), reproductive factors , as well as medical and smoking history. Fresh frozen normal breast tissues were collected from Mehr-e-Sina Surgical Center, Sohrevardi Surgery Center, and Vali-e-Asr Clinic in Imam Khomeini Hospital in Tehran. Samples were divided into two groups: parous (n = 24) and nulliparous women (n = 27) and were stored at -80 °C, until DNA extraction was accomplished. Genomic DNA was extracted using the high salt method[25]. Isolated DNA was used as a template for MeDIP-quantitative polymerase chain reaction (qPCR) process. In this cross-sectional study, 51 normal breast tissue samples were collected from women who were mammoplasty candidates without a positive history of breast cancer or other forms of malignant diseases. The present work was approved by the local Ethical Committee of Tehran University of Medical Sciences , and all participants signed the informed consent form. They also filled out a questionnaire regarding age, BMI Epigentek, USA, Cat. No # P-1015). After extraction, DNA (1 μg) was sheared by sonication to obtain fragments ranging from 200 to 1000 bp. DNA was denatured at 95 °C for 5 minutes and was then divided into input (IN) and immunoprecipitated fractions. The immunoprecipitated fraction was incubated with anti-5′-Methylcytosine monoclonal antibody at room temperature for 1 hour and subsequently, was washed twice with 150 μl of antibody buffer and then with wash buffer. Finally, DNA was eluted from the column according to the kit instructions. Quality control of MeDIP and relative fold enrichment was performed by qPCR reaction using TAKARA SYBR Premix Ex Taq II (Tli Plus)  by Corbett rotor gene 6000 cycler . To carry out these steps, two pairs of primers were designed to detect CpG islands of H19 imprinted control region (which is methylated) and GAPDH promoter (an unmethylated housekeeping gene) as MeDIP positive and negative controls, respectively (http://bio.kuas.edu.tw/urpd/) was employed to design the primers. The thermal cycling started with an initial step at 95 °C for 40 seconds to activate the hot-start DNA polymerase. Subsequently, a two-step cycling profile was done as follows: 40 cycles of annealing/ extension at 95 °C for 15 seconds and 60 °C for 35 seconds. To confirm the amplification of the PCR target region, the amplification step was followed by a melting cycle from 70 °C to 99 °C  by real-time qPCR . Relative enrichment of target locus was normalized by positive control (H19 gene) and calculated with the 2-∆∆ct formula.After accomplishing quality control for MeDIP, the enriched DNA fragments in MeDIP were quantified for target gene  were analyzed by Mann-Whitney U test. Moreover, non-parametric spearman correlation test was employed to calculate the correlation between FOXA1 methylation and both age and breastfeeding durations. All analyzes were done by IBM SPSS Statistics version 22. Two tailed p values of less than 0.05 were considered statistically significant. Data were represented by median and interquartile range or frequency and percentage. Non-parametric Mann-Whitney U test was used to compare FOXA1 gene body methylation levels in normal breast tissue of early parous with nulliparous women. The MeDIP fold enrichment ratio and the specificity for all samples were in acceptable range; the means of them were 14663 and 98%, respectively, showing that MeDIP was performed successfully, and H19, as a methylated gene, was enriched 14663 times more than GAPDH, as an unmethylated control gene. The first group was early parous women  who had experienced their first full-term pregnancy under 25 years, and the second group was nulliparous women  who had never experienced pregnancy. All participants in this study were cancer-free Iranian women. The differences in methylation levels of studied subgroups are presented in FOXA1 relative methylation level in parous group is significantly higher than nulliparous (p = 0.041), as indicated in FOXA1 methylation in parous group was around twofold higher than nulliparous women .  In this study, we used qPCR following MeDIP to compare FOXA1 gene body methylation; the results of these analyses are displayed in FOXA1 methylation and both age and breastfeeding duration through spearman's correlation test.We found no association of reproductive (breastfeeding duration and number of deliveries) and non-reproductive factors  with [1], the exact molecular mechanisms underlying this effect has remained unclear. Researchers hope to prevent or postpone the breast cancer in women at risk such as nulliparous women by some molecular interventions. This prevention policy requires discovering and understanding molecular changes that occur with early parity in normal breast tissue of women and lead to breast cancer protection. Early age at FFTP is a known modifiable and a natural protective factor against breast cancer in women worldwide. Although this phenomenon was recognized many years ago[24] and parity[17]. Hence, it is possible that these lifelong epigenetic alterations, which are influenced by women’s lifestyle, can play a crucial role in the protective effect of pregnancy[27]. According to previous studies, the effect of early pregnancy on hormone responsiveness of breast tissue, especially estrogen hormone, is one of the proposed mechanisms of parity-associated breast cancer protection[4]. Therefore, we assume that studying the effects of early parity on some genes such as ESR1 and FOXA1, which have important functions in estrogen responsiveness[18], can improve the better understanding of underlying mechanisms of early pregnancy associated with breast cancer protective effect.  DNA methylation is a kind of epigenetic change that can be inducible and stable with a strong link to lifestyle-dependent features, such as BMI. This result is consistent with the notion that the malignancy process can affect molecular status in tumor cells and make them different from normal cells. Following these investigations, in the present study, we decided to focus on the influence of early pregnancy on FOXA1 gene methylation, which is an upstream regulator of ERS1 gene. Evidence from one study on normal breast tissue samples of a small group of American women (19 parous vs. 16 nulliparous) has shown the association of early FFTP with gene body hypermethylation of FOXA1 by MBD-Cap technique[17]. In the current study, for investigating these new findings in a different larger study population, we evaluated 51 normal breast tissue samples of Iranian women with another quantitative epigenetic method (MeDIP-qPCR), which is more efficient for the investigation of gene body methylation in comparison with MBD-Cap method[28]. Our findings demonstrated that early parity has significant correlation with gene body hypermethylation of FOXA1. This finding is compatible with the results from the previous study[17]. In our two previous studies, we showed that ESR1 methylation status has a significant association with FFTP in the breast tumors, but we did not find this association in normal breast tissues[18]. This gene has high expression levels in luminal progenitor cells of the normal breast tissue, and their epigenetic status can be modified by early pregnancy. Moreover, it has been shown that early parity is related to FOXA1 epigenetic modification in epigenome mammary of mouse models[30]. In this case, researchers have shown that epigenetic modifications increase in FOXA1 gene during mice gestation, which in turn correlates with down-regulation of FOXA1 mRNA expression[30]. Thus, according to these findings[30], which are in line with our results, it seems that FOXA1 gene hypermethylarion is a new candidate epimark that is modified by early pregnancy in normal breast tissue. Regarding the protective role of early FFTP against ERα+ breast tumors and its influence on methylation status of FOXA1 gene (as an upstream regulator of ERα)[18], it can be hypothesized that early pregnancy may change estrogen responsiveness of normal mammary tissue and result in protection against breast cancer. FOXA1 is a pioneer transcription factor that co-localizes with ERα at enhancers in the genome and also is essential for ERα’s function[7-9]. Hence, we attempted to investigate whether these reproductive factors could alter FOXA1 gene body methylation in normal breast tissue or not. Regarding our results, there was no association between these factors and FOXA1 methylation levels. It seems that the protective effect of lactation and the increased number of births against breast cancer do not act through the same molecular mechanisms of early FFTP. Epidemiological studies have shown that reproductive factors such as prolonged breastfeeding duration and increased number of births can lead to reduction in the risk of breast cancerFOXA1 methylation. It seems that non-reproductive factors cannot influence the epigenetic status of FOXA1 gene in normal breast tissue. However, regarding our limited sample size, these results should be interpreted with caution and are required to be clarified in future investigations with a larger sample size.Based on our results, non-reproductive factors such as BMI, age, and smoking do not have any significant association with FOXA1 in normal breast tissue. Because of limited sample size and lack of FOXA1 expression analysis in this research, more investigation is needed to clarify the molecular mechanisms underlying this association with the aim of identifying promising new ways to advance breast cancer prevention strategies[32].In conclusion, it seems that early parity, as an important breast cancer protective factor, can induce epigenetic changes in normal breast tissue. Also, all protective reproductive factors perhaps do not have similar effect on epigenetic status of normal breast tissue and may reduce the risk of breast cancer through different mechanisms. Our study provides a new hint about the association between early FFTP and epigenetic alterations within gene body of


Neurofibromatosis type 1 (NF1) is a cancer predisposing syndrome. Studies suggest that women < 50 years old (y.o.) with NF1 have an increased breast cancer (BC) incidence and BC associated mortality. However, this has not been widely recognized secondary to small study populations.A systematic literature review was conducted through database searches for BC and NF1: 3456 articles identified, 166 reviewed, 58 used for descriptive analysis and 4 utilized for meta-analysis. Fisher’s exact tests, Kaplan-Meier curves and random-effects meta-analysis models were used for analysis.p = 0.005). Median survival for the entire cohort was 5 years vs. the reported median BC survival of over 20 years in the general population using the SEER database. Median age at BC death was 48.5 years; 64% of deceased patients were <  50. Meta-analysis of a total of 4178 women with NF1 revealed a BC standardized incidence ratio (SIR) of 3.07 (95%CI 2.16–4.38) for women with NF1 vs. the general population. Women < 50 y.o. demonstrated a higher SIR of 5.08 (95%CI 3.77–6.81) compared to 1.92 (95%CI 1.40–2.63) if ≥50 y.o.Two hundred eighty-six cases of NF1 and female BC were identified with a median age of 46 years at diagnosis; 53% were <  50. Peak age of BC diagnosis was between 34 to 44 years. Women < 50 y.o. presented with more advanced disease vs. those ≥50  contains supplementary material, which is available to authorized users. NF1) gene located on chromosome 17q11.2, with a heterozygous mutation having nearly 100% penetrance [NF1 gene is 282.7 kilobase pairs in length, contains 60 exons, and encodes neurofibromin [NF1 gene has one of the highest rates of spontaneous mutations in the entire human genome [Neurofibromatosis type I NF1) is one of the most common autosomal dominant genetic disorders in humans and has a reported incidence of 1 in 2000 to 3000 live births with most population based studies demonstrating a prevalence of the clinical diagnosis in 1 in 3000 to 1 in 5000 individuals  is one o, 7. NF1 netrance . The NF1Neurofibromin functions as a tumor suppressor gene through regulation of Ras guanosine triphosphatase activity, inhibiting GTPase activation, and regulating cell proliferation and differentiation , 7. LossA link between NF1 and breast cancer has been suggested in several cohort and epidemiological studies , 17–22 aThe guidelines published by the Meta-analysis of Observational Studies in Epidemiology (MOOSE) group were followed to complete the meta-analysis  case-control or cohort-based study design; (ii) investigation of the association between NF1 and breast cancer incidence; (iii) presented standardized incidence ratio (SIR), relative risk (RR), odds ratios (OR), or hazard ratio (HR) estimates with 95% confidence intervals (CI) or sufficient data with which to calculate these. The exclusion criteria were (i) abstracts without full texts, (ii) unpublished studies, (iii) lack of available data, (iv) male sex and (v) the following types of articles: news, previews, reviews, comments, and discussions.The following data from each included study were extracted: first author, publication year, country, study design, sample size, number of cases/controls, diagnostic criteria, age at time of breast cancer diagnosis, follow-up duration, breast cancer stage at time of diagnosis, breast cancer subtype, development of bilateral breast cancer, development of other primary cancers, development of metastatic breast cancer, survival outcome, and effect sizes  with 95% CI and adjusted factors. Data were independently extracted and analyzed by two investigators and a final decision was reached by consensus. The methodological quality of the studies included in the meta-analysis was assessed using the Newcastle-Ottawa Scale (NOS) . NOS scoRough comparisons of the NF1 patients with breast cancer identified in this study were made to the general population using data reported in the Surveillance Epidemiology and End Results (SEER) database for the years 1975–2012 . Age disDescriptive statistics were provided to summarize patient characteristics and outcomes for the two NF1 age groups. For those variables in categories, Fisher’s exact test was used for testing across groups. Kaplan-Meier curves were used to estimate survival probabilities for the collected NF1 cases, and compared to the matched survival probabilities of general population from SEER database. To statistically combine estimates from studies that contained sufficient information, we used random effects meta-analysis models . The logThe search strategy resulted in 3796 records: 89 from PubMed, 2572 from PMC and 1135 through examination of reference lists. After excluding duplicated reports, 166 full-text articles were identified on the basis of language, title, and abstract. After further evaluation, 101 records were excluded due to male sex, the lack of NF1 diagnosis, benign breast disease, review article, duplicate data, neurofibromatosis type 2, and non-primary breast cancer. A total of 58 eligible articles published between 1933 and 2015 were identified and were included in the descriptive analysis , 35–84. Among the 58 studies included in the descriptive analysis, 41 were case reports, one was a case series, 13 were retrospective cohort studies, two were prospective cohort studies, and one was a cross-sectional cohort study. Two hundred and eighty-six cases of NF1 and female breast cancer were identified. The female NF1 patients with breast cancer originated from 23 different countries, with the majority of them originating from the United States of America (38%), United Kingdom (31%), and Japan (12%). Characteristics of these cases are described in Table Of the 286 cases identified, 181 reported the age of the patient. Mean age at breast cancer diagnosis was 49.3 years with a median age of 46 years and an interquartile range of 38.3 to 58.0 years. The majority of the patients were <  50 years of age with 53% <  50 years old, 28% between 35 and 44 years old and 15% < 35 years old. Age distribution of the incidence of breast cancer identified in these NF1 cases was evaluated based on their age at the time of diagnosis and revealed a peak age of diagnosis between the ages of 34 to 44 years. This incidence of breast cancer cases was compared to the SEER database for reported breast cancer age distribution of incident cases, which demonstrated a peak age of diagnosis between the ages of 55 to 64 years in the general population  was the most commonly reported breast cancer subtype (75.5%). The other 176 breast cancer cases were identified as breast carcinoma. Breast cancer stage at time of diagnosis was reported in 54 cases (27 cases of patients < 50 years of age and 27 cases of patients ≥50 years of age). When analyzing all the female NF1 patients with breast cancer, the majority presented with stage I or II disease. However, when separated by age, women < 50 years of age presented with more advanced disease compared to those ≥50 years of age  and two were from the United Kingdom (UK). These studies involved a total of 4178 female participants with NF1 who were being followed and documented 87 reported cases of breast cancer. The characteristics of these studies are summarized in Table 2 = 44%). However, women with NF1 < 50 years of age demonstrated a higher SIR of 5.08 (95% CI: 3.77–6.81) compared to 1.92 (95% CI: 1.40–2.63) in those ≥50 years of age. For both age groups, very low heterogeneity was observed with I2 values less than 5%. Similar results were found using a fixed-effects model (data not shown).The unadjusted SIRs for each study and the combined SIR of breast cancer in women with NF1 are presented in Fig. The association between NF1 and increased risk of malignant tumors has been widely described with the most commonly reported associations being gliomas and malignant peripheral nerve sheath tumors –14. CaseDescriptive analysis of these 286 reported cases of NF1 and female breast cancer demonstrated a median age of 46 years at time of breast cancer diagnosis, compared to 62 years in the general population reported in the SEER database. The peak age of breast cancer diagnosis in these NF1 women was between 34 to 44 years. NF1 women younger than 50 years of age were found to have more advanced disease at the time of their breast cancer diagnosis (56% presenting with stage III-IV disease) compared to those 50 years of age or older (22% presenting with stage III-IV disease). The median survival for all of the identified cases of NF1 women with breast cancer was 5 years compared to the reported median breast cancer survival of over 20 years in the general population using the SEER data base. The median age at time of breast cancer death was found to be 48.5 years in this group of NF1 breast cancer cases compared to 68 years in the general population reported in the SEER database. These findings suggest that there is a high incidence of breast cancer in NF1 women younger than 50 years of age and that these women tend to present with more advanced disease and possibly experienced an increased breast cancer related mortality. However, it is important to note that true comparison with SEER database is difficult with this cohort of patients as these patients originated from 23 different countries and the survival reported in the USA SEER database may be better than in some other countries included in this cohort.To our knowledge, this study is the first meta-analysis to evaluate the association between women with NF1 and the risk of developing breast cancer. Findings of this meta-analysis of 4 cohort studies, following a total of 4178 female patients with NF1, indicate that women with NF1 have a three-fold increased risk of developing breast cancer compared to the general population . Additionally, a higher-than-expected number of breast cancer cases were identified in women with NF1 who were younger than 50 years of age, giving a five-fold increased risk of breast cancer in this age group compared to women younger than 50 years old in the general population . Women with NF1 who were 50 years of age and older demonstrated a smaller increased risk of breast cancer compared to women 50 years and older in the general population. This lower increased risk of breast cancer in older NF1 patients may be due to the fact that women with NF1 develop breast cancer at a younger age than the general population. Given this early elevated risk a fair number of the susceptible NF1 population may develop breast cancer prior to 50 years of age, thereby decreasing the number of susceptible women in the older population.In addition to the four studies included in this meta-analysis, several other cohort and epidemiological studies have suggested an association of breast cancer in young women with NF1. In 1972 Brasfield et al. described a cohort of 110 NF1 patients from the USA looking at the biologic behavior and the natural history of this disease. Herein, he found that 5 of 54 (9.3%) females, one of them 39 years old, developed breast cancer and noted that all patients with breast cancer died within 5 years of the breast cancer diagnosis . FollowiWalker et al. conducted a prospective population based cohort study of 448 NF1 patients  to evaluate the incidence and type of malignant tumors in this population in the UK. In this study, five (1.8%) females developed breast cancer and the risk of breast cancer was found to be significantly higher in NF1 patients younger than 50 years of age compared to this age group in the general population; SIR = 4.0 (95% CI: 1.1–10.3) . In thisGiven the rarity of breast cancer events described, especially when divided by age groups, it is important to evaluate a large defined population. This meta-analysis was able to assess the risk of breast cancer in a large defined patient population. The strengths of the present meta-analysis include less influence exerted by small-study bias, a moderate-to-high quality of studies included in the meta-analysis, and very low heterogeneity observed for both age groups. However, this study has several limitations. First, the associations presented are unadjusted. Due to the lack of reporting across studies, other known confounding risk factors for breast cancer, such as medications, smoking, use of hormone replacement therapy, parity or other reproductive factors cannot be accounted for. Thus, one cannot exclude residual or unmeasured confounding as the alternative explanation of these results. Second, given that the number of available cohort studies was limited, this study has a potential to be limited by publication bias. It is possible that a number of neuro-fibromatosis centers have assessed breast cancer in their cohorts without finding evidence of an increased risk and that these findings have not been published. Third, referral bias may be present in two of the included studies , 20. RefThis systematic literature review and meta-analysis suggests that women with NF1 less than 50 years of age have a five-fold increased risk of breast cancer, present with more advanced disease, and may have an increased breast cancer related mortality. The findings of this study support the notion that it may be reasonable to consider NF1 in conjunction with other hereditary breast cancer syndromes. Early breast cancer screening guidelines need to be extended to include women with NF1. Given that this study demonstrated a peak age of breast cancer diagnosis between 35 and 44 years of age in these patients with NF1, this study provides further evidence for early breast cancer screening starting at 30 years of age in women with NF1. Guidelines recently produced by the National Comprehensive Cancer Network (NCCN) now suggested early screening for NF1 patients beginning at age 30 . HoweverNF1 gene is included in some of the breast cancer screening genetic panels as deleterious mutations on the NF1 gene have been associated with a two to four fold increased risk of breast cancer [NF1 gene in patients not previously known to have NF1. Given that approximately 50% patients with NF1 have de novo mutations [With the recent improvement and reduced cost of DNA sequencing technology, the use of multigene panels for clinical genetic testing of patients with a high risk of hereditary breast cancer has increased . The NF1t cancer . The goat cancer . Howeverutations , patientNF1 gene has been implicated as a breast cancer driver with somatic mutations reported in 27.7% of all breast carcinomas [NF1 gene may also result in, or predispose cells to, a mutation in other genes on that same chromosome [NF1 gene and BRCA1 gene are both on chromosome 17, about 20 centiMorgan (cM) apart, and it has been suggested that there may be an interaction between these two genes [NF1 gene without any clinical evidence of NF1 is not clear.The rcinomas , 16. Preromosome . The NF1wo genes , 81. HowNF1 gene, along with several other genes associated with increased risk of breast cancer, identified by clinical genetic testing of patients with breast cancer. After exclusion of BRCA1, BRCA2, and syndromic breast cancer genes , observed pathogenic variants in ATM, BARD1, CHEK2, PALB2 and RAD51D were associated with high or moderately increased risks of breast cancer [NF1 pathogenic variants and an increased risks of breast cancer [NF1 gene may have not been associated with an increased risks of breast cancer; 1) it is likely that patients with NF1 are selected out of testing due to their know diagnosis or other socioeconomic factors and 2) lack of appropriate controls [NF1 constitutional mutation types and breast cancer risk in patients with NF1 and breast cancer showed that different NF1 variants demonstrated different risks of breast cancer and that nonsense and missense mutations may be associated with a higher breast cancer risk [Couch et al. recently evaluated the risk of breast cancer associated with inactivating variants of the t cancer . But, pat cancer . Severalt cancer –94. Howet cancer . Their rcontrols . Additiocer risk .NF1 pathogenic variants identified in patients undergoing clinical genetic testing on breast cancer risk in individuals without clinical evidence of NF1.The increased risk of breast cancer found in this meta-analysis and other previous studies reinforces that increased attention to the breast cancer risk in young women with NF1 is needed. Appropriate physician and patient education with increased awareness of the association of early onset breast cancer in patients with NF1 and the need for early breast cancer screening is crucial for this patient population. Continued education of the general public and primary health care providers will allow for appropriate implementation of the most recent NCCN breast cancer screening guidelines in all young women with NF1 starting at 30 years of age. Furthermore, additional studies are required to assess the influence of Additional file 1:Meta-analysis of Observational Studies in Epidemiology (MOOSE) Checklist. Checklist with brief description of how research criteria of observational studies in epidemiology were handled for reporting of background, search strategy, methods, results, discussion, and conclusion in the meta-analysis. (PDF 306 kb)


Considering the lack of efficient breast cancer prediction models suitable for general population screening in China. We aimed to develop a risk prediction model to identify high-risk populations, to help with primary prevention of breast cancer among Han Chinese women.A cause-specific competing risk model was used to develop the Han Chinese Breast Cancer Prediction model. Data from the Shandong Case-Control Study (328 cases and 656 controls) and Taixing Prospective Cohort Study  were used to develop and validate the model. The expected/observed (E/O) ratio and C-statistic were calculated to evaluate calibration and discriminative accuracy of the model, respectively.Compared with the reference level, the relative risks (RRs) for highest level of number of abortions, age at first live birth, history of benign breast disease, body mass index (BMI), family history of breast cancer, and life satisfaction scores were 6.3, 3.6, 4.3, 1.9, 3.3, 2.4, respectively. The model showed good calibration and discriminatory accuracy with an E/O ratio of 1.03 and C-statistic of 0.64.We developed a risk prediction model including fertility status and relevant disease history, as well as other modifiable risk factors. The model demonstrated good calibration and discrimination ability.The online version of this article (10.1186/s12885-019-5321-1) contains supplementary material, which is available to authorized users. Breast cancer is one of the most prevalent malignancies among women worldwide . AlthougBRCA gene mutation rate, is lower in the Chinese population than those in Western countries [Competing risks are said to be present when an individual is at risk for more than one mutually exclusive event, such as death from a different cause, and the occurrence of one of these competing events will prevent the event of interest from ever happening. A cause-specific hazard model considers competing risks and therefore has better performance than the Cox model when used for disease risk prediction. Gail proposed a method to estimate individual probabilities of developing breast cancer, based on a cause-specific hazard model . Severalountries . The aimAll participants were selected from the study population of the project “Ministry-affiliated Hospital Key Project of the Ministry of Health of the People’s Republic of China (No. 07090122)”. We conducted a population-based case-control study in Shandong Province to develop the prediction model, which was then validated in the Taixing Prospective Cohort Study. The study protocol was approved by Shandong University and informed consent was obtained from all study participants.In the population-based Shandong Case-Control Study, which was conducted from 2008 to 2012, the target population included 25- to 70-year-old women of Han ethnicity, with over 2 years of local residence and at least 6 months of local residence at the time of the survey. Breast cancer patients were from the department of breast surgery at the Second Hospital of Shandong University. All patients were newly diagnosed with breast cancer. Each eligible patient who had been pathologically diagnosed with breast cancer was matched with two healthy controls according to age (± 2 years) and location (neighbor or co-worker in the same region). Finally, 328 cases and 656 controls were included in the Shandong Case-Control Study. Details of the questionnaire used in this study are described elsewhere .n = 18,657), after excluding participants with missing data of risk factors (n = 116). Among 18,541 eligible participants, 5365 participants were lost to follow-up. The rate of lost to follow-up was 28.9% . Finally, 13,176 individuals were enrolled. New incident cases of breast cancer were identified from local cancer registries and via active follow-up telephone and face-to-face interviews. The flow chart of the enrollment in these two studies was shown in Fig. In the Taixing Prospective Cohort Study, 18,681 participants who completed a questionnaire in 2008 were included as the baseline population, and outcomes were collected after 7 years of follow-up. Participants who have not been diagnosed with breast cancer at baseline were selected for the study  of developing breast cancer, we applied the cause-specific hazard model approach , accordi(1) We estimated the relative risks (RRs) and attributable risk (AR) in the Shandong Case-Control Study.To estimate RRs, odds ratios (ORs) and the corresponding 95% confidence intervals (CIs) were calculated in conditional logistic regression for matched data using the above variables and coding, as described in Table (2) We calculated age-specific baseline hazards for breast cancer (based on the breast cancer incidence rate of the Cancer Surveillance System of the Taixing Centers for Disease Control) and for competing events .Twelve age groups were defined . The baseline hazard was defined as the hazard rate for each individual whose risk factors were at the lowest risk level. The baseline hazards of breast cancer were estimated by multiplying the age-specific breast cancer incidence rates by (1 – estimated population AR).(3) We combined baseline hazards (for breast cancer and competing events) and RRs to estimate probabilities in the developed Han Chinese Breast Cancer Prediction (HCBCP) model. The absolute risks were calculated according to initial age, follow-up duration, and initial RRs in the HCBCP model. A simple computing method for individualized risk assessment was performed .(4) Finally, the Taixing Prospective Cohort Study was used to validate the HCBCP model. We used E/O ratios  to assess model calibration. The C-statistic, which is the probability that a randomly chosen positive instance will rank higher than a randomly chosen negative one, was used to evaluate the model’s discriminatory ability.SAS version 9.4  was used to perform data cleaning and to calculate RRs. We used R  to develop the HCBCP model; the corresponding code is provided in Additional file Table RRs were estimated using multivariate conditional logistic regression. Risk factors that were significant in univariate ordered logistic regression , who was age 27 years at the first live birth (code = 1), no history of benign breast disease (code = 0), BMI of 27 (code = 1), with a family history of breast cancer (code = 1) and life satisfaction score of 7 (code = 0); the RR is derived as 2.512 × 1.895 × 1 × 1.372 × 3.250 × 1 = 21.23. Thus, in this example, the 20-year absolute risk would be 2.71% with RR of 20.0 . Receiver operating characteristic (ROC) curve analysis was performed to evaluate the discrimination ability of the HCBCP model. Figure We compared the HCBCP model with the Gail model in the Taixing Prospective Cohort Study. Owing to a lack of information for the number of biopsies and biopsy atypical hyperplasia among study participants, these predictors were marked as unknown. The E/O ratio and 95% CI was 2.39 , and the C-statistic was 0.54 . The results showed that the Gail model tended to overestimate the absolute risks in the Taixing cohort. The Health risk appraisal (HRA) model , a risk We developed a risk prediction model for breast cancer for use in Han Chinese women. The results of validation showed good calibration and discriminative ability, with E/O ratio 1.03, and C-statistic 0.64 . Using this model, women with a high risk of developing breast cancer can be identified using simple data collection. With the model, women identified as having high risk can be selected for further breast cancer-related examination, such as mammographic screening. Consequently, there is greater likelihood of identifying women with early-stage breast cancer. Women with higher risk might be motivated to maintain their current health status and take measures to prevent or delay the onset of breast cancer.Competing risk is commonly existing in disease risk prediction. Traditional survival analysis models (like the Cox model) treat deaths from competing causes as independent censoring events. Hence, bias would be induced into risk prediction . The proSelection of the risk factors included in the current model was based on a systematic review of epidemiological studies as well as statistical analyses. In this study, we assessed a variety of factors that are considered to be associated with breast cancer including: number of abortions, age at first live birth, benign breast disease history, BMI, diabetes, breast cancer family history, and life satisfaction score; most risk factors have been confirmed in previous studies.The relationship between diabetes and breast cancer is controversial. In our study, diabetes was a risk factor in univariate logistic regression ; therefore, the precision of the validation estimates may be affected. Fourth, owing to the administrative jurisdiction, the rate of loss to follow-up in the validation study was high and may bias the results. Hence, further studies in other areas of China are needed, to validate the performance of this model.There were also some limitations in our study. First, gene markers were not included in this model, which would lead to a decrease in the discriminative power. Second, we conducted the model using the age-specific breast cancer incidence rate and non-breast cancer mortality rate in Taixing; therefore, application of this HCBCP model may vary by geographic region. Third, the number of incident cases in the Taixing study was small Additional file 2:Table S1. Relative Risk (RR) and 95% confidence interval (95% CI) of risk factors associated with breast cancer by univariate conditional logistic regression in Shandong Case Control Study (DOCX 15 kb)Additional file 3:Table S2. The age-specific breast cancer incidence rates and non-breast cancer mortality rates of Taixing in 2015 (DOCX 14 kb)Additional file 4:Questionnaire. An English language version of the questionnaire used in this study (PDF 84 kb)


Given rising rates of breast cancer in parts of Asia, immigrant Asian American women in the United States may have higher rates of breast cancer than previously anticipated. This study examined breast cancer risk among Asian American women by nativity and percentage of life lived in the United States, accounting for established breast cancer risk factors.We analyzed a breast cancer case-control data set of Asian American women living in the San Francisco Bay Area; this data set included 132 cases of women with breast cancer selected from a Surveillance, Epidemiology, and End Results cancer registry and 438 Asian American women without diagnosed breast cancer matched to cases by age and country of origin. We used logistic regression to compare 3 Asian American groups: US-born, immigrants who lived 50% or more of their life in the United States, and immigrants who lived less than 50% of their life in the United States.In the minimally adjusted and fully adjusted models, both groups of immigrant Asian American women had higher risk of breast cancer than US-born Asian American women. In the fully adjusted model, compared with US-born Asian American women, immigrant Asian American women who lived more than 50% of their life in United States were on average 3 times as likely  and immigrants who lived less than 50% of their life in United States were on average 2.46 times as likely  to have breast cancer. We found no difference in fully adjusted odds ratios of having breast cancer between the 2 immigrant groups.This study provides preliminary evidence that breast cancer risk among immigrant Asian American women may be higher than among their US-born counterparts. Research in the United States has found that among Asian Americans, risk for female breast cancer was higher among US-born women than among women born outside the United States.This report finds that this trend, in a more recent cohort of Asian Americans, may be shifting, such that breast cancer risk is higher among women who are immigrants compared with those who are US-born.There may be an increased need for breast cancer treatment services for immigrant Asian Americans as well as for continued efforts to increase access to mammograms among all Asian American women.Research in the United States has consistently found that for racial/ethnic minority populations such as Asian Americans, those not born in the United States have lower rates of female breast cancer than their US-born counterparts ,2. HowevWorldwide, breast cancer incidence is high in North America and relatively low in Asia . AlthougCurrent US immigration policies have led to the influx of highly skilled Asian immigrants who perhaps have a higher socioeconomic status than previous immigrant groups. In 2013, 51% of recent East and South Asian immigrants in the United States had at least a college degree; in 1970, only 20% of all immigrant arrivals had this level of education . ConsistOur study adds to the existing literature by describing how breast cancer risk among Asian American women varies by nativity status and percentage of life lived in the United States, accounting for established breast cancer risk factors, and it is among the first to do so. We hypothesized that 1) breast cancer risk would differ by nativity, 2) a greater percentage of life lived in the United States would be associated with higher breast cancer risk, and 3) modifiable risk factors, including reproductive history and body mass index (BMI) ,13, woulWe used a population-based case-control data set of Asian American women. We collected data from the Asian Community Health Initiative, a case-control study of breast cancer among Asian American women in the San Francisco Bay Area . The Sanwww.armyofwomen.org). The third strategy used monthly advertisements and posts on Craigslist, Facebook, Twitter, and listservs reaching Asian Americans. A fourth strategy used traditional address-based sampling of a randomly generated sample of 3,000 residential addresses of people with Asian American surnames; this strategy yielded a response rate of less than 2%. The fifth strategy involved disseminating flyers at health fairs, senior centers, community events, and fundraisers.Because selection bias can result from relying on a single recruitment method, the Asian Community Health Initiative used several methods to recruit women for the control sample . The IniInitiative researchers frequency-matched controls to cases by Asian country of origin  and age  in a 3:1 ratio of controls to cases. Researchers found the control sample to be representative of the overall population of Asian American women in the San Francisco Bay Area in comparisons of key demographic characteristics with data from the California Health Interview Survey (CHIS) .Recruitment took place from March 2013 through October 2014 and yielded an analytical sample of 570 Asian American women consisting of 132 cases and 438 controls. Survey data were collected through telephone interviews and self-administered questionnaires in English, Chinese, or Tagalog. Written materials for Chinese and Tagalog were translated and independently back-translated. Participants received a $30 check for completing the telephone interview. Participants in the second-phase self-administered survey received an additional $15. Participants consisted of Chinese (53%), Filipina (20%), and other Asian American (27%) women aged 22 to 87 . Among immigrant women, the average age at immigration was 22 . All study procedures were approved by the ethical review boards at the Cancer Prevention Institute of California, University of California–Los Angeles, and the University of California–Riverside.The outcome was breast cancer . The independent variable of interest was nativity and percentage of life lived in the United States .We adjusted for the following established breast cancer risk factors: pregnancy history , family history of breast cancer , and menopausal status and use of hormone replacement therapy (HRT) . We also adjusted for BMI, calculated as the respondents’ reported weight in kilograms divided by the square of their height in meters. We adjusted for BMI because it is positively associated with higher risk of breast cancer among postmenopausal women  and becaAdditional covariates were socioeconomic status, operationalized as education level , home ownership , and health insurance status . All study variables were self-reported.For each study variable, we calculated frequency and percentage by breast cancer status. We then used unconditional logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs) of breast cancer risk. Models were minimally adjusted for age group  and country of origin  . Fully aAdditionally, we analyzed whether other risk factors were associated with breast cancer, including physical activity, smoking status, alcohol use, and oral contraceptive use. In this sample none of these variables were associated with having breast cancer, and they were excluded from the final model.A lower percentage of Asian American women with breast cancer (17% [22 of 132]) were US-born compared with controls (33% [144 of 438]) . A greatP = .06), but the lower limit of the CI just included the null. After we adjusted for potential confounders in the fully adjusted model, immigrant Asian American women still had higher risk of breast cancer than US-born Asian American women . We found no difference in fully adjusted odds ratios of having breast cancer between the 2 immigrant groups .Minimally adjusted ORs show that immigrant Asian American women had higher risk of breast cancer than US-born Asian American women . The risk of breast cancer was only slightly higher among immigrant Asian American women who lived ≥50% of their life in the United States compared with immigrant Asian American women who lived <50% of their life in the United States  , suggestSecular changes in breast cancer risk factors and the resulting increases in breast cancer rates in Asian countries, especially in affluent areas, may further explain our finding ,4. The cOther findings in our study coincide with previous findings on breast cancer among Asian American women. Greater breast cancer risk was associated with higher socioeconomic status, measured as home ownership and health insurance status ,24. GiviOur study had several limitations. One limitation was the relatively small sample size. A second was that the case and control subsamples were matched according to Asian country of origin, so we were unable to disaggregate the various Asian American subpopulations. A third limitation was the case-control design, which did not allow us to examine trends over time. Lastly, our study was conducted only in the San Francisco Bay Area, so our results may not be generalizable to the larger population of Asian American women in the United States. The San Francisco Bay Area is unique in its relative affluence and the characteristics of the Asian immigrants it attracts, so our findings may not apply to other areas of the United States, especially less affluent areas. Nevertheless, as with the research on breast cancer in Marin County in the San Francisco Bay Area ,28, the Clinicians who serve Asian American patients should be aware of the potential trend of higher breast cancer risk among immigrant Asian American women and allocate resources for breast cancer treatment among this demographic accordingly. Interventions are needed to increase breast cancer screening among both immigrant and US-born Asian American women to prevent breast cancer from progressing. Immigrant Asian American women likely have different barriers to screening and treatment than US-born Asian American women, including language and culturally appropriate care.Future studies are needed to corroborate the novel findings of our research. Studies using larger samples in broader geographic areas should compare breast cancer risk among Asian Americans by nativity and explore possible explanations for differences. Cross-national studies that examine breast cancer risk in the country of origin and upon immigrating to the United States would be useful. Such research could illuminate our understanding of how breast cancer risk changes over time, especially in an environment of international migration and changing contextual risk factors. Such investigations can lead to better breast cancer prevention activities, especially among immigrant groups living in the United States.


Flight attendants are an understudied occupational group, despite undergoing a wide range of adverse job-related exposures, including to known carcinogens. In our study, we aimed to characterize the prevalence of cancer diagnoses among U.S. cabin crew relative to the general population.In 2014–2015, we surveyed participants of the Harvard Flight Attendant Health Study. We compared the prevalence of their self-reported cancer diagnoses to a contemporaneous cohort in the National Health and Nutrition Examination Survey (NHANES 2013–2014) using age-weighted standardized prevalence ratios (SPRs). We also analyzed associations between job tenure and the prevalence of selected cancers, using logistic regression and adjusting for potential confounders.n = 2729), flight attendants (n = 5366) had a higher prevalence of every cancer we examined, especially breast cancer, melanoma, and non-melanoma skin cancer among females. SPR for these conditions were 1.51 , 2.27 , and 4.09 , respectively. Job tenure was positively related to non-melanoma skin cancer among females, with borderline associations for melanoma and non-melanoma skin cancers among males. Consistent with previous studies, we observed associations between job tenure and breast cancer among women who had three or more children.Compared to NHANES participants with a similar socioeconomic status  contains supplementary material, which is available to authorized users. Flight attendants are a highly understudied occupational cohort that is consistently exposed to several known and probable carcinogens in the cabin environment . These iUntil 2014, flight attendants were excluded from Occupational Safety and Health Administration protections typically granted to U.S. workers, and only limited protections (such as with regard to blood-borne pathogens) were implemented in 2014. Flight attendants’ exposure to ionizing radiation is still not monitored or regulated in any way, despite the fact that cabin crew are exposed to the largest average annual effective dose relative to all other U.S. radiation workers . StudiesTo address gaps in the literature, we launched the Harvard Flight Attendant Health Study (FAHS) in 2007 . In the Our participants were enrolled in the second wave of the FAHS, an ongoing study of flight attendant health which was established in 2007 and originally enrolled 4011 flight attendants . For theAny current or former U.S. flight attendant was eligible to participate in the FAHS . While Wave 1 of the FAHS restricted participants to flight attendants employed by two U.S. airlines, Wave 2 was open to any U.S. flight attendant. Hence, participants in the current study worked for a wide range of airlines, flying both domestically and internationally. We collected 1642 surveys from returning participants, which represents a 40% response rate from the original cohort with still-valid addresses. In total, the 2014–2015 FAHS cohort enrolled 5366 U.S. flight attendants with information on age and gender. These variables were among the last questions to be asked in the online questionnaire and are thus indicators of survey completeness. Our study was approved the Harvard T.H. Chan School of Public Health Institutional Review Board, and all participants provided their written informed consent.Our survey instrument included validated questions about self-reported health outcomes and symptomology, work experiences, and personal characteristics , 11, takWe compared the prevalence of cancers reported in the FAHS to equivalent information collected from a nationally representative sample from the NHANES during the years 2013–2014 . We restWe compared the prevalence of self-reported cancers in the NHANES and FAHS using the Standardized Prevalence Ratio (SPR), an indirect method of standardization which compares observed and expected prevalence given rates in the reference study population, which in our case was the NHANES . The SPR2), and educational attainment ; breast cancer models were further adjusted for number of live births. Tenure was meant to serve as a proxy for the duration of occupational exposures [We analyzed gender-stratified associations between net job tenure  and self-reported cancers using logistic regression and adjusting for potential confounders: age (continuous), current and past smoking status (yes/no for both), current overweight status based on body mass index . For breast cancer, we evaluated these associations both overall and stratified by parity . Parity categories were chosen based on previous studies of breast cancer among cabin crew , 21. We We report characteristics of both FAHS and NHANES participants in Additional file We report SPRs comparing the prevalence of cancer diagnoses in the FAHS and the NHANES in Table We also found associations between each five-year increase in net job tenure as a flight attendant and non-melanoma skin cancer among females , with borderline associations for melanoma and non-melanoma skin cancers among males   among this occupational group relative to the general population. This is striking given the low rates of overweight and smoking among flight attendants in our study population, which we take to be indicators of general health and healthy behaviors, as well as being independent risk factors for some cancers , 11. We Our finding of a greater prevalence of breast and skin cancers among flight attendants is consistent with most of the epidemiologic literature on this topic to date –11. As nOur results are also consistent with cabin crews’ occupational exposures to ionizing radiation , 6, CircWe report associations between duration of employment as a flight attendant and breast cancer risk among women who had three or more children, with some evidence of an association among nulliparous women as well, though the latter association was imprecise. Nulliparity is a risk factor for breast cancer, and women who are parous may be less susceptible to the effects of carcinogenic exposures on the breast due to breast cell differentiation occurring after a first pregnancy , 33. HenLimitations of our study include its cross-sectional design, which precludes inferences about causality, as an observed association may reflect the effect of flight attendant work on a given condition, or the effect of an outcome on a factor related to employment as a flight attendant. Use of structured questionnaires, as in our study, aims to minimize this bias. We also note a further limitation that the date of cancer diagnosis was not recorded in the FAHS questionnaire. Hence, some reported cancers may have been diagnosed prior to employment as a flight attendant, and some flight attendant work (i.e. exposure) may have occurred following a cancer diagnosis, making the direction of the potential bias unclear. These limitations are counteracted in part by our analyses evaluating job tenure prior to age 40 and 45 years in relation to cancer prevalences, as many cancers, including of the skin and breast, occur later in life. Therefore, this restriction increases the probability that the exposure of interest occurred prior to the reported cancer outcome.Another potential limitation of our study involves the question of whether a population of flight attendants is sufficiently comparable to the general U.S. population with regard to cancer risk factors, and whether differences in risk factors may introduce bias to the SPRs. For example, we report substantial differences in racial profile, smoking status, overweight prevalence, and number of live births between the FAHS and NHANES cohorts, all of which are related to the risk of various cancers. We have counteracted this issue in part by restricting the NHANES comparison group to currently employed adults with at least a high school degree and above a certain income to poverty ratio, and by conducting sensitivity analyses restricting to non-Hispanic white participants that showed no meaningful differences from our main results. We also note that the FAHS includes a substantially smaller percentage of current smokers and overweight participants than the NHANES population, which would be expected to decrease the risk of several cancers, whereas we consistently observed increased cancer SPRs. At the same time, we should note that FAHS participants had fewer children than NHANES participants (which elevates the risk of breast cancer), though this is in part ameliorated by the fact that we observed associations between tenure as a flight attendant and breast cancer within parity subgroups. Even with the above reported sensitivity analyses, we acknowledge that the potential for residual confounding by cancer risk factor profile differences between the two study populations (such as for race and parity) still exists.In addition, health outcomes in our study and in the NHANES were based on self-report; validation through medical records was not possible due to the scope and cost of this endeavor. Validity of self-reported health outcomes varies by study population and the outcome of interest. Sensitivity and specificity of self-reported outcomes relative to medical records or linkage to disease registries were found to be moderate to high for common cancers (including breast cancer and melanoma), particularly among those with higher socioeconomic status, such as in our well-educated cohort . HoweverA further limitation of our study is that we recruited flight attendants from a mix of company rosters, on-site airport recruitment, and an online/social media presence. Recruiting volunteer participants not recruited from employee files may have contributed to selection bias. For example, volunteer participants may differ from those recruited using a more randomized approach in terms of various factors, including their socioeconomic status, attitude toward health research, and factors related to time and ability to complete online surveys , as discussed in a recent analysis with regard to online recruitment in the Heart eHealth Study relative to NHANES . HoweverOur study may have attracted a disproportionate number of flight attendants with cancer, leading to detection bias, as flight attendants with worse health are likely to be more motivated to participate in an epidemiological study of flight attendant health, are likely to attend regular medical check-ups , and the question of cancer risk in relation to flight exposures is well known within the aviation community. However, it is reassuring that our results are consistent with previous studies that recruited participants from employee rosters –10.Additional limitations of our study include reliance on job tenure as a surrogate for occupational exposures, lack of correction for multiple testing, insufficient power to evaluate less common cancers, and insufficient information on confounders for some cancers. In particular, we were not able to control for leisure-time UV exposure when evaluating skin cancer risk, though it should be noted that a large study found no difference in sunbathing habits between flight attendants and the general population . We planStrengths of our study include access to the resources of a large cohort of cabin crew with information on a range of cancer outcomes, work experiences, and potential confounders. In addition, online questionnaires are an increasingly popular option in epidemiologic research, including high profile studies such as the Millennium Cohort and the Nurses’ Health Study 3 . This moOur study findings contribute to the sparse literature on flight attendant health, which may also be applicable to passengers, especially frequent flyers. Conducting high quality studies within this group of workers is important given that U.S. cabin crew are subject to fewer protections than most workers in this country and relative to flight attendants working in the European Union (EU). For example, the EU requires airlines to monitor radiation dose, organize schedules to reduce radiation exposure, and inform workers of current studies .We have conducted a large and comprehensive study characterizing cancer prevalence rates among flight attendants relative to the general population. Despite low smoking and obesity levels indicative of positive health behaviors, we report that flight attendants have elevated rates of several cancers, especially breast, melanoma, and non-melanoma skin cancers. These results are consistent with previous findings regarding flight crew health. Ours is the first study to report an elevated rate of non-melanoma skin cancer in a U.S. flight attendant cohort (consistent with European studies). Some of these cancers were also related to tenure as a flight attendant, overall or within subgroups of parity in the case of breast cancer. Our results yield information to guide future research regarding the health of this understudied group of workers, which can also be considered when evaluating how to improve health and quality of life among cabin crew.Additional file 1:Table S1. Participant Characteristics, Harvard Flight Attendant Health Study (2014–2015) and NHANES (2013–2014). (XLS 13 kb)Additional file 2:Table S2. Comparative age-adjusted cancer prevalence in the Harvard Flight Attendant Health Study  and NHANES (2013–2014), evaluating only flight attendants with occupational smoking exposure prior to the year 1988. (XLS 10 kb)


Fully automated assessment of mammographic density (MD), a biomarker of breast cancer risk, is being increasingly performed in screening settings. However, data on body mass index (BMI), a confounder of the MD–risk association, are not routinely collected at screening. We investigated whether the amount of fat in the breast, as captured by the amount of mammographic non-dense tissue seen on the mammographic image, can be used as a proxy for BMI when data on the latter are unavailable.Data from a UK case control study (numbers of cases/controls: 414/685) and a Norwegian cohort study (numbers of cases/non-cases: 657/61059), both with volumetric MD measurements (dense volume (DV), non-dense volume (NDV) and percent density (%MD)) from screening-age women, were analysed. BMI (self-reported) and NDV were taken as measures of adiposity. Correlations between BMI and NDV, %MD and DV were examined after log-transformation and adjustment for age, menopausal status and parity.I2 statistics.Logistic regression models were fitted to the UK study, and Cox regression models to the Norwegian study, to assess associations between MD and breast cancer risk, expressed as odds/hazard ratios per adjusted standard deviation (OPERA). Adjustments were first made for standard risk factors except BMI  and then also for BMI or NDV. OPERA pooled relative risks (RRs) were estimated by fixed-effect models, and between-study heterogeneity was assessed by the r = 0.74 in the UK study and r = 0.72 in the Norwegian study) and with DV . Both %MD and DV were positively associated with breast cancer risk in minimally adjusted models : 1.34  and 1.46 , respectively; I2 = 0%, P >0.48 for both). Further adjustment for BMI or NDV strengthened the %MD–risk association ; I2 = 0%, P = 0.33 and 1.51 ; I2 = 0%, P = 0.32, respectively). Adjusting for BMI or NDV marginally affected the magnitude of the DV–risk association ; I2 = 0%, P = 0.87 and 1.49 ; I2 = 0%, P = 0.36, respectively).BMI was positively correlated with NDV (adjusted When volumetric MD–breast cancer risk associations are investigated, NDV can be used as a measure of adiposity when BMI data are unavailable. Mammographic density captures the amount of (radio-)dense tissue in the breast. Mammographic density, for a woman’s age and body mass index (BMI), is a well-established breast cancer risk factor , 2. ThisMammographic density has traditionally been assessed as the absolute or relative amount  occupied by the dense tissue which appears on a mammographic image as white “cotton-like” patches. Percent mammographic density (%MD) is negatively correlated with BMI , whiThe recent introduction of full-field digital mammography (FFDM), paralleled by the development of fully automated digital image assessment software, has meant that mammographic density assessment is now routinely performed in many screening settings, thus providing a unique opportunity for the conduct of large-scale studies on this biomarker of risk. However, a common barrier to such investigations is the lack of information on a woman’s BMI as data on this variable are rarely collected at screening.Most of the fully automated density assessment methods developed for FFDM attempt to estimate from the two-dimensional images, the volume of radio-dense tissue (DV) as well as the volume of non-dense (fat) tissue (NDV) and the total volume of the breast (BV) which, in Western populations, is highly correlated with NDV. Hence, NDV, or its BV correlate, has been used as a proxy for BMI in analyses of mammographic density and breast cancer risk in studies where BMI data are not available , 8. HoweThe present analysis was conducted within two studies: a case control study from the UK and a cohort study from Norway.n = 414) were women with newly diagnosed breast cancer at the Royal Marsden Hospital (RMH), London, between April 2010 and July 2012. Controls (n = 685) were women screened and found to be breast cancer-free at the Central and East London Breast Screening Service (CELBSS) in the same time period. The CELBSS invites women between 50 and 70 years of age for mammographic screening once every 3 years as part of the English National Health Service Breast Screening Programme. Women over 70 years can optionally contact the service for a self-referred appointment every 3 years.The study methodology of the UK case control study is described in detail elsewhere . In shor2. Ethnicity was categorised in accordance with the census classification as “White”, “Black” (African or Caribbean), “Asian”  and “Other” [Data on breast cancer risk factors, including age, ethnicity, parity, menopausal status, use of oral contraceptives, use of hormone therapy and self-reported height and weight, were collected by a self-administered questionnaire at the time of screening for controls and within 15.5 months of the diagnostic mammography for cases. BMI was calculated as weight in kg/(height in m) “Other” .3) of the total breast (BV), non-dense (fat) tissue (NDV) and dense (fibro-glandular) tissue (DV) separately for each one of the four breast/view images, and percent mammographic density (%MD) was estimated as DV/BV×100.Participants underwent full-field digital mammography, with two views  and mediolateral-oblique (MLO)), of both breasts. The images were taken on Senographe DS machines . The anonymised raw images were analysed by using Volpara version 1.0  . This aln = 970), a ductal carcinoma in situ (DCIS) diagnosis up to 6 months after the screening date (n = 224) and a bilateral breast cancer (n = 11) were excluded.The Cancer Registry of Norway is responsible for the administration of BreastScreen Norway (the Norwegian Breast Cancer Screening Program). All women within a targeted age-range of 50–69 years resident in the country are invited to undergo mammography screening every 2 years. From August 2006 to 2014, women who underwent mammographic screening in the nationwide programme were asked to complete a questionnaire on a number of standard breast cancer risk factors and a second questionnaire on current exposure to risk factors. Included in the present study were women who participated in BreastScreen Norway in four counties, had information on volumetric mammographic density from their first mammographic screening between 2007 and 2014, and had completed both questionnaires. However, for the second questionnaire on current exposures, if the questionnaire or certain values were missing, information from the questionnaire completed at a previous screening round was used (approximately 16.5%). The cohort consisted of 61,716 women, including 657 women who were diagnosed with a first occurrence of breast cancer during a median follow-up from date of screening of 3.84  years. Women with a previous diagnosis of breast cancer  or MDM L50 or MDM L30 machines (Phillips). The raw images were read by Volpara version 1.5.0  to obtain, similarly to the UK study, volumetric estimates of BV, NDV, DV and %MD.The UK study was approved by all relevant ethics committees . The Norwegian study was approved by the Regional Committee for Medical and Health Research ethics in the South-East Health Region of Norway. In the UK, participants provided written informed consent. In the Norwegian study, in accordance with the Cancer Registry Regulations, returning the questionnaire was considered consent, and information about screening examinations can be used for quality assurance and research if the women have not actively opted out. About 2% of the women attending the programme have opted out.Descriptive analysis of UK controls and the full Norwegian cohort included examination of the distributions of BMI and volumetric mammographic measurements. For these analyses, measurements were averaged over the four images . Natural-log transformations were applied to average %MD, DV, NDV and BMI to normalise their distributions. Scatter plots and Pearson’s correlation coefficients were used to examine BMI associations with %MD, DV, NDV and BV. BMI and each mammographic measure were regressed on age at mammogram, parity and menopausal status using linear regression (including controls only in the UK study and the full cohort in the Norwegian study). Pearson’s correlation coefficients between the residuals derived from these models were then calculated (and denoted r) to allow examination of correlations that are not influenced by these variables.For the UK case control analysis, the average density measures from the CC and MLO images from the unaffected breasts for cases and for a randomly selected breast for controls were used. In order to compare the association of %MD and DV with the odds of breast cancer, after adjusting for different sets of confounders, three different logistic regression models were fitted where these two exposures were first standardised as recommended previously . The resr = 0.99; P = 0.001), its interpretation is made more difficult by the fact that it reflects both DV and NDV.The first  model controlled for age (continuous), menopausal status  and parity (yes/no).  %MD and DV with breast cancer risk, expressed in terms of hazard ratios and referred to as OPERA HRs.Three different models were fitted as in the UK study; the first was minimally adjusted for screening year , menopausal status  and parity (yes/no) (further adjustment for country of birth as a proxy for ethnicity did not affect the findings). A second model was additionally adjusted for BMI, and a third model was additionally adjusted for NDV in place of BMI. In all, 10,288 participants, including 99 cases, were excluded from all three models because they missed data for at least one of the variables listed.Three further models were also fitted to the Norwegian data using the full reproductive and lifestyle risk factor questionnaire data collected in this study . In the first model, BMI was omitted; in the second model, BMI was included; in the third model, NDV was used instead of BMI. In total, 25,833  women with missing data on any of the variables examined were excluded to ensure that these additional models were fitted to the same subset of women. Departure from the proportional hazards assumption underlying each of these fitted models was evaluated by using tests based on Schoenfeld residuals. The Akaike information criterion (AIC) corresponding to each multivariable model from the two countries is also reported.Similar analytical steps were followed to study the associations between BMI and breast cancer risk, and then NDV and breast cancer risk, in both studies, in each case adjusting for age, menopausal status and parity.I2 statistic [Fixed-effects models were used to obtain pooled summary OPERA relative risk (RR) estimates from the two studies. Between-study heterogeneity was assessed by the Q statistic and the tatistic .P value of less than 0.05. All analyses were conducted in Stata  [In all the analyses, we considered statistical significance (two-sided) at a The baseline characteristics of the participants in the two studies are shown in Table r = 0.74) and in the Norwegian (r = 0.72) study. In contrast, the correlation between DV and BMI was weakly positive in both the UK study (r = 0.33) and the Norwegian study (r = 0.25). Consequently, %MD was negatively correlated with BMI in both the UK (r = −0.66) and Norwegian (r = −0.57) studies. The correlation between %MD and DV was only moderate after adjustment for age and BMI in the UK (r = 0.33) and Norwegian (r = 0.55) studies (data not shown). Further analyses showed that the findings were robust after stratification by mammographic view, age at mammography and, for the UK study, restricting the analysis to White women (data not shown).The distributions of self-reported BMI and of NDV, the volumetric measurement that reflects the fatty tissue in the breast, were right-skewed in the UK control group and in the full Norwegian cohort Fig. . Table 2P > 0.30 and P > 0.10, respectively, in models that included interactions with either menopausal status or age), most likely because of the relatively small number of younger  women in either study. There was no evidence of an association between NDV and breast cancer risk adjusting for the same covariates as for BMI ; Norwegian study OPERA HR 1.01, 95% CI 0.93, 1.09).There were weak positive associations between BMI and breast cancer risk  in both the UK  0.95, 1.26) and the Norwegian  studies. The magnitude of the BMI–risk association was not modified by menopausal status or age in either study . Further adjustment for BMI showed a strengthening of the positive association between %MD and breast cancer risk: the magnitude of the pooled OPERA RR increased from 1.34  to 1.51  upon adjustment for BMI and there was no evidence of between-study heterogeneity for the latter . Replacing BMI with NDV, as a proxy for level of adiposity, yielded the same strength of association between %MD and breast cancer risk with the pooled OPERA RR increasing to 1.51  and there was no evidence of between-study heterogeneity .Figure I2 = 0%; P = 0.87). Adjusting for BMI had little impact on the magnitude of the DV–breast cancer risk association . When BMI was replaced by NDV, the magnitude of the pooled OPERA RR increased only slightly to 1.49  and there was no evidence of between-study heterogeneity .The association between DV and breast cancer risk was slightly stronger than that found for %MD in the minimally adjusted model  and there was no evidence of between-study heterogeneity  preferable.Further analyses of the OPERA estimates in the Norwegian data show that the magnitude of the associations of %MD and DV with breast cancer risk was little changed by adjustment for additional reproductive and lifestyle factors in the subset of women with information on these variables. The addition of BMI to this expanded model strengthened the association between %MD and breast cancer risk; the OPERA HR increased from 1.24  to 1.39 . Likewise, replacing BMI with NDV to control for adiposity led to similar estimates  though with a marginally better fitting model using AIC. In contrast, adjustment for BMI or NDV had little effect on the magnitude of the DV–breast cancer risk association  and breast cancer risk, adjustment for BMI or NDV had little or no impact on the magnitude of the association. All of these estimates of association are expressed in terms of units per relative standard deviation of the exposure . This allows us to compare estimates while adjusting for different sets of potential confounders, in units that account for the strength of association between the confounders and the exposure of interest . Both thAfter adjustment for age, parity and menopausal status, BMI was found to be strongly positively correlated with NDV but strongly negatively correlated with %MD. In contrast, BMI was weakly positively correlated with DV. The observed strong positive BMI–NDV correlation is consistent with findings from area-based mammographic studies , 6, 15. The present study found a positive, albeit weak, association between BMI and breast cancer risk, reflecting the predominantly peri-/post-menopausal status of the participants, but no association between NDV and breast cancer risk. There is little evidence for an NDV–breast cancer association from volumetric studies to date, but a meta-analysis of data from 13 area-based studies has reported an overall inverse association between mammographic non-dense area and risk  albeit wStrengths of this investigation include the availability of data from two independent studies of women of screening age. Both studies used the same objective volumetric density assessment method, making the two datasets comparable. In addition, the Norwegian study was population-based and had a very large sample size and detailed data on a wide range of potential confounding variables collected prior to breast cancer diagnosis and therefore was unlikely to have been affected by recall bias. Furthermore, although other studies have assumed that it is reasonable to used NDV as a surrogate for BMI , 8, we bA limitation of this investigation is that it relied on self-reported BMI. Previous research suggests that women tend to understate their weight and overstate their height, particularly those who are overweight or obese , 23, altWe used the OPERA approach to allow comparison across different exposures . It is argued that this provides a fairer comparison of the different risk gradients across the different models . HoweverThe study was restricted to women of screening age and not generalizable to younger women. There is also evidence that the relationship between percent body fat and BMI is dependent upon ethnicity , 27, witFinally, both studies were based on a particular volumetric mammographic density assessment approach. It would be worthwhile to examine the extent to which the present findings can be replicated when alternative methods of assessment of volumetric mammographic density are used.The availability of fully automated methods to measure mammographic density enables the integration of such measurements within screening programme settings, thus facilitating the conduct of large-scale studies, including research on whether screening should be tailored to a woman’s individual risk. A perceived barrier to the conduct of such studies is the lack of information on a woman’s BMI. This study shows that the association between DV and breast cancer risk is not confounded by BMI or NDV and hence no adjustment for these variables is required. In contrast, the association between volumetric %MD and risk is confounded by level of adiposity and adjustment for either BMI or NDV yields similar results. Adjustment for NDV may offer some advantages over BMI as the NDV measurements are objective, being generated by a fully automated algorithm, and thus do not suffer from measurement errors associated with self-reported BMI. Furthermore, in most breast screening settings, it is not feasible to collect BMI data; therefore, NDV values are potentially very valuable because they will be automatically available for every woman screened. Nevertheless, these findings need to be replicated in other populations, particularly among those with a different age and ethnic mix.