Familial risks for testicular cancer (TC) are among the highest of all cancers. However, data are limited for histological types of TC and for possible familial associations of TC with other cancers. We used the nationwide Swedish Family-Cancer Database for years 1958 to 2015 to analyse familial relative risks (RR) for 11,138 TC patients when first-degree relatives were diagnosed with TC or other cancer in reference to those without a family history. A total of 191 familial TCs were found, which accounted for 2.0% of all TC. The RR was 5.06 when one family member was diagnosed with TC with no significant difference between seminoma and nonseminoma. However, the risk for nonseminoma was 33.59 when two family members were affected. Internally consistent familial associations of TC, particularly of seminoma, were found with breast and nervous system cancers and melanoma. Individual significant associations were found for a number of sites, including ovarian, endometrial and prostate cancers. Our results suggest that nonseminoma may have a stronger genetic background than seminoma but seminoma shares more familial associations with discordant cancers. Clustering of TC with hormone-dependent cancers of the breast, ovary, endometrium and prostate may suggest mechanistic links and possibly gene-environment interactions. In Europe, the incidence of TC has dramatically increased, concomitantly with an equally dramatic decrease in mortality3. Differences in incidence between the countries have been among the largest for any cancer. The increasing trend has been described as a birth cohort effect but in the high-incidence Scandinavian countries the increase has leveled off4. Precursor lesions of TC are thought to arise and accumulate as a result of aberrant fetal gonocyte development and these in-situ lesions gain invasive phenotype in early adulthood6. Individual risk factors of TC include cryptorchidism, hypospadias, inguinal hernia, subfertility and other lower risk birth-related factors8. Some of these factors are understood to be related to androgen insufficiency6. Environmental pollutants have been associated with the risk of TC; e.g. the type of organochlorine compounds among endocrine disruptive chemicals8. The role of environmental factors was documented among low-risk Finnish immigrants to Sweden whose TC incidence was only 0.45 of the Swedish rate9. The risk of TC in Sweden-born sons of Finnish immigrant parents was no longer different from native Swedes, which implies a strong environmental influence in spite of the 100% Finnish genotype9. In a family study on cancer etiology, TC was found to be the cancer with the highest proportion of childhood shared environmental effects among all assessed causes10. These results combined suggest that environmental factors during childhood and adolescence affect TC risk11. Finding these factors and their possible interactions with host genetic background would likely help to resolve the issue of increasing incidence trends.The incidence of testicular cancer (TC) varies with ethnic origin and with economic state, the incidence being highest in developed countries and lowest in developing countries12. Approximately 1.8% of TC patients have a father or a sibling diagnosed with TC12. According to a Nordic TC study, the risk of seminoma in brothers (SIR 4.2) was not different from the risk of all TC in brothers (4.1)13. TC has been shown to be associated with other (discordant) cancers in families including lung, kidney and oesophageal cancers, melanoma, leukaemia and non-Hodgkin lymphomas15. Our previous study covered the years 1958 to 2002 and used data from the Swedish Family-Cancer Database14. As we have recently updated the database with cancers up to the year 2015, we decided to revisit, here in this study, familial associations of 11,138 TCs with TC and discordant cancers.Familial risk of TC is among the highest of all cancers but the risk is significantly higher if the affected family member is a brother (6.94) rather than a father (3.90), which is likely related to birth cohort effectsWe identified a total of 11,138 TC of which 9711 were identified in offspring generations used in the RR calculations. Seminomas (6120) outnumbered nonseminomas (4729) in the total population and among the offspring generations (5133 and 4391). The median diagnostic ages for seminoma were higher (38 years) than for nonseminoma (29 years) for all, and in the offspring generations these were 36 and 28 years respectively. All cancers in the database amounted to 1.96 million, of which 701,617 were diagnosed in the offspring generations.Table Table In Table Analyses were also carried out for nonseminoma (data not shown). RRs for nonseminoma were not increased with any discordant cancer. However, prostate cancer was increased to 1.15 when 201 sons were diagnosed with nonseminoma (1.00–1.32), and other male genital cancers were increased to 2.36 when six sons were diagnosed with nonseminoma (1.06–5.26). All cancers were increased to 1.07 when 1245 sons were diagnosed with nonseminoma (1.01–1.13).TC has been associated with some other cancers as described in the introduction but the advantage of the present study is its size and its design in aiming at internal validation of the results in partially independent two-way analyses. We could show that all testicular cancers were associated with breast cancer and melanoma in both of the two-way analyses. Single significant associations were found with lung, ovarian, prostate and nervous system cancers. Most site-specific associations of TC were for seminoma, which was associated with melanoma in two ways, and with nervous system cancer in two different family types. Associations of seminoma with individual significant sites included pancreatic, lung, breast, endometrial and prostate cancers and Hodgkin and non-Hodgkin lymphomas. Site-specific associations of nonseminoma only included single significant results with prostate and other male genital cancers. Seminoma showed several discordant associations with other cancers, which may be related to an 8-year later onset compared to nonseminoma and underlying mechanistic differences.15. It, however, appears noteworthy that, in addition to breast cancer, other hormone-dependent female sites were associated with TC in single analyses including ovarian and endometrial cancers, and prostate cancer was an associated male site. These are common cancers and the magnitude of relative risk was rather modest. It may, however, be premature to consider such a clustering of hormone-dependent cancers to be fortuitous.Single discordant familial associations, listed above, may be of interest but they may also be chance findings and thus need to be confirmed in independent settings. Associations of TC with breast and nervous system cancers and melanoma were confirmed in at least two separate analyses and only the association with melanoma was reported previously13. Genome-wide association studies (GWAS) have identified some 50 single nucleotide polymorphisms (SNPs), which increased the risk of TC and many of these suggest disruption of developmental transcriptional regulation of germ cell differentiation as a basis of TC susceptibility17. It is, however, not well-known if SNPs may differentiate risks of seminoma and nonseminoma. The involved pathways cover KIT/KITLG/MAPK signalling, telomerase function, microtubule assembly and DNA damage repair16. The most prominent gene is KITLG that shows an allelic risk of 2.55 with a high population frequency of 0.8 for the risk allele18. The gene encodes the ligand for tyrosine-kinase KIT, which is commonly somatically mutated in seminomas. It has been calculated for 39 independent SNPs that these accounted for 37% of the (father-to-son) familial risk of TC17. The calculated polygenic risk score for men in the top 1% of genetic risk have a risk of 14, translating to a 7% lifetime risk of TC16. These data can be compared with our lifetime risk calculations in the Nordic familial setting13. The lifetime risk in the population was 0.6% and it was 2.3% for the brother of an affected individual, increasing to 10.3% for persons with multiple affected family members. As most of the present familial cases  were affected brothers. Therefore, one can conclude that empirical familial risk and polygenic risk scores only partially overlap.Although concordant familial risks for TC are well-known, the present results contributed to the notion that nonseminoma appeared to be more genetically predisposed than seminoma because the risks were very high in families where more than two males were affected but case numbers were few8.In summary, nonseminoma appeared to show higher familial associations with TC than seminoma but seminoma had many more familial associations with other cancer than nonseminoma. Associations of TC with breast and nervous system cancers and melanoma were internally consistent and mostly novel. Clustering of TC with hormone-dependent cancers of the breast, ovary, endometrium and prostate may have pathophysiological underpinnings, which could be related to interactions of endocrine disruptive chemicals or other unknown environmental factors with the host genetic background19. The Swedish “Multigeneration Register” was linked by the individually unique national registration number to the Cancer Registry for the years 1958–2015 to make the basis of the Family-Cancer Database. In the Database families are organized in subsequent generations. The Swedish personal number is issued to all permanent residents upon birth or immigration to Sweden. The completeness of the cancer registry is considered to be over 90%20. The cancer site is registered using diagnostic codes according to the 7th (and later) revisions of the International Classification of Diseases (ICD-7). Patients diagnosed with TC were identified as were all other cancers in family members. The histological classification of TCs was used, as present in the Cancer Registry, to define seminoma and non-seminoma.In the Swedish “Multigeneration Register” individuals who were born in Sweden in 1932 and onwards are registered with their parents. We define these as the offspring and parental generation, respectivelyst, 1958, whichever came latest. Follow-up was terminated on diagnosis of first cancer, death, emigration, or the closing date of the study, which was December 31st, 2015. Parents’ ages were not limited but sons were 0 to 83 years of age; siblings could be defined only in the offspring generation.Relative risks (RRs) were used to measure cancer risks for TC in the offspring generations according to occurrence of cancers in their first-degree family members . The parental generation born before 1932 was diagnosed with 1427 TC and served as probands only and were not used for person-year calculations. In one family TCs were diagnosed in three generations, and the person in the middle generation was entered separately as a case and a proband. In the reverse analysis, RR was calculated for cancer in offspring when family members were diagnosed with TC. These two types of analyses were partially independent, particularly for discordant cancers, and positive results in both analyses provided strong support for a true association. Follow-up was started for each offspring at birth, immigration or January 1Poisson regression modeling was employed to estimate RRs and corresponding 95% confidence intervals (CI). Potential confounders, including sex, age group (5-year bands), period (5-year bands), socioeconomic status , residential area  were added to the model as covariates. SAS version 9.4 was used to perform the statistical analysis.The study was approved by the Ethical Committee of Lund University and the study was conducted in accordance with the approved guidelines not requesting informed consent. The study is national register-based study on anonymous personal data.


We read with interest the article by Thigpen et al. . With 34The masking potential of dense tissue to hide detection of breast cancer or an “abnormality” is included in 28 existing laws (not including Iowa’s law which has vague language on this issue or North Dakota’s law which expired 31 July 2017), but only 14 (not including Maine’s “suggested” communication) mention supplemental screening. Even when supplemental screening is mentioned, none of the state laws inform women that adding screening ultrasound or MRI can detect cancer not visible with mammography, as Thigpen et al. suggest.www.DenseBreast-info.org to provide medically sourced information to patients and healthcare providers to assist in such shared decisions.Successful communication of the increased risk of developing breast cancer and the masking potential associated with dense breast tissue is of great importance and should be considered together with other risk factors. High-risk women of any breast density should be identified and offered screening MRI and possible genetic testing. Tomosynthesis (3D mammography), while an improvement on conventional mammography, has not been shown to improve cancer detection in extremely dense breasts . It is e


BRCA1/2 mutation carriers is unknown.Height and body mass index (BMI) are associated with higher ovarian cancer risk in the general population, but whether such associations exist among BRCA1/2 (CIMBA) data set, comprising 14,676 BRCA1 and 7912 BRCA2 mutation carriers, with 2923 ovarian cancer cases. We created a height genetic score (height-GS) using 586 height-associated variants and a BMI genetic score (BMI-GS) using 93 BMI-associated variants. Associations were assessed using weighted Cox models.We applied a Mendelian randomisation approach to examine height/BMI with ovarian cancer risk using the Consortium of Investigators for the Modifiers of 2 increase in observed and genetically determined BMI, respectively. No association was found for postmenopausal women. Interaction between menopausal status and BMI was significant (Pinteraction < 0.05).Observed height was not associated with ovarian cancer risk . Height-GS showed similar results . Higher BMI was significantly associated with increased risk in premenopausal women with HR = 1.25 (95% CI: 1.06–1.48) and HR = 1.59 (95% CI: 1.08–2.33) per 5-kg/mBRCA1/2 mutation carriers is consistent with findings in the general population.Our observation of a positive association between BMI and ovarian cancer risk in premenopausal  Penetrance of BRCA1/2 mutations is likely modified by other genetic variants and lifestyle or reproductive factors.9 Investigation of these factors could aid in implementation of strategies to reduce ovarian cancer risk among mutation carriers.Ovarian cancer is the fifth leading cause of cancer deaths in US women, due to its typically advanced stage at presentation.11 In the general population, both height and BMI appear to be positively but inconsistently associated with risk of ovarian cancer.14 Previous studies also showed that the association between BMI and ovarian cancer was stronger in premenopausal women.16 Because of differences in age at onset and tumour histology/grade, risk factors for ovarian cancer might be different for BRCA1/2 mutation carriers than women in the general population.17 Only one case–control study, with 469 ovarian cancer cases, has examined anthropometric measurements in BRCA1/2 mutation carriers and found that neither height nor BMI were related to ovarian cancer risk.18 Larger, adequately powered studies are needed to assess whether a relationship between either height or BMI and ovarian cancer risk exists for BRCA1/2 mutation carriers, and whether the direction of association is concordant with that in the general population.Both height and BMI are quantitative traits with substantial genetic bases. In recent genome-wide association studies (GWAS), numerous genetic variants were found to be associated with these traits.21 Compared to traditional epidemiologic approaches, MR can reduce biases such as reverse causation and residual confounding, which can interfere with causal interpretations. However, the MR approach requires that the genetic variants are associated with the exposure, the variants are not or only weakly associated with confounding factors in the causal pathway, and the variants only affect disease risk through the exposure (i.e. absence of pleiotropic effects).21 To the degree that these assumptions are met, the MR approach can strengthen the evidence for a causal relationship between exposure and disease.Mendelian randomisation (MR) methods use genetic markers associated with a trait as an instrumental variable (IV) to assess their potential relationship with a disease outcome.BRCA1/2 (CIMBA) with 22,588 participants. We examined heterogeneity of these associations with respect to the mutation carried (BRCA1 vs BRCA2), menopausal status, tumour histology, and tumour grade.Herein, using traditional epidemiologic and MR methods, we conducted analyses of height and BMI and their association with ovarian cancer risk in the Consortium of Investigators for the Modifiers of 24Characteristics of the CIMBA consortium and information on specific genotyping protocols are provided in P < 5 × 10−8).25 SNPs with low imputation quality (<0.5) were excluded, leaving 586 SNPs for height and 93 for BMI. Supplementary Tables From the latest publications of the Genetic Investigation of Anthropometric Traits, we identified single-nucleotide polymorphisms (SNPs) associated with height or BMI at genome-wide significance level P < 5 × 0−8.25 SN24 Briefly, we calculated the weighted sums of all of the height- and BMI-associated variants under additive models, which do not include interactions between variants. Namely, we used the formulas: βXGi is the literature-reported per-allele magnitude of association of the ith SNP for height and BMI, respectively. A scaling factor was calculated by regressing each GS against its respective trait among non-case carriers. The corresponding regression coefficients were β0 (intercept = 165.455) and β1 (slope = 5.217) for height and β0 (22.607) and β1 (5.523) for BMI. In the present study, BMI-GS was scaled to BMI at the date of questionnaire, rather than BMI at age 18 years, as previous GWAS were based on BMI measurements in middle-aged adults.Calculation of the height and BMI genetic scores (GS) was described in detail previously.BRCA1/2 carriers.27 We applied a robust sandwich variance-estimation approach to the risk estimates to account for non-independence among multiple carriers per family. In addition, we performed subgroup analyses by BRCA1/2 mutations and menopausal status. Menopausal status was defined as a time-varying covariate, coded as premenopausal from birth until age at natural menopause or bilateral salpingo-oophorectomy. For individuals with missing age at menopause, we imputed the age as 50 years. Imputing missing age at menopause as 46 years did not materially change the results. The mean and median ages at natural menopause in this population were 46 and 48 years, respectively. All analyses were adjusted for the first eight principal components (to account for ethnicity and population stratification), birth cohort, and country of enrolment. Additional analyses assessed the associations of height and BMI with ovarian cancer subgroups by histological type (serous vs. non-serous) and by tumour grade (well or moderately differentiated tumours vs. poorly or undifferentiated).We subsequently modelled each scaled GS against ovarian cancer risk using weighted Cox models. Our primary outcome of interest was ovarian cancer diagnosis, with individuals censored for breast cancer diagnosis, risk-reducing bilateral salpingo-oophorectomy, death, or end of follow-up, whichever occurred first. Owing to the study design of CIMBA, weights in the model were applied for cases and non-cases based on previously observed incidence of ovarian cancer in βXGi for each SNP i, which represents the per-allele magnitude of association with height or BMI from previous GWAS. Next, we calculated βYGi and G , principal components, birth cohort, BRCA mutation, and country of enrolment. The overall causal association (βYX) is calculated using inverse-variance weighted estimate of each variant’s effect: 28 Egger’s test was used to assess for possible pleiotropic effects of the variants (i.e. whether variants influence the outcome through other pathways), to ensure that this assumption held.29In addition, phenotype associations with each individual height and BMI variant were assessed and pooled using inverse variance-weighted meta-analysis. The individual associations were obtained by first extracting 30 In stage one, observed height or BMI was regressed against the corresponding GS, principal components, birth cohort, country, and mutation status. In the second stage, we used a Cox model to fit ovarian cancer risk against height or BMI, birth cohort, country, mutation status, and residuals from stage one. Variance estimates were obtained through 10,000 boot-straps  and Stata 14.0 . A two-sided BRCA1 and 7912 BRCA2 mutation carriers, are shown in Table BRCA1: 2319; BRCA2: 604). Compared with non-cases, participants who developed ovarian cancer were more often parous women, were younger at first live birth, and were from earlier birth cohorts. At the date of questionnaire/interview, height measurement was available for 7657 participants and BMI measurement for 7516 participants. Most tumours for BRCA1/2 mutation carriers were invasive, of serous, poorly, or undifferentiated grade, and stages 3 or 4 at diagnosis, characteristics which are consistent with prior reports.31Characteristics for the 22,588 individuals in the CIMBA consortium, comprising 14,676 P = 0.31)  = 1.07 per 10-cm increase, 95% confidence interval (CI): 0.94–1.23, P < 10−24)  (λ). Among the SNPs that were combined, there was a low degree of heterogeneity (I2 = 0%). Examining small-study effects using Egger’s test did not suggest likely pleiotropic effects. In the two-stage residual inclusion analysis, the estimated relative risk was larger though with wide CIs, which overlapped with those derived using other methods .Combining the effects of all 586 height-associated variants using inverse-variance weighted meta-analysis, we obtained similar findings , whereas no association was found in postmenopausal women , with significant interaction (P = 0.02). We found that BMI was a significant predictor of non-serous ovarian cancer risk  but not for serous ovarian cancer .After multivariable adjustment, we found a nonsignificant positive association between BMI at the date of questionnaire completion and ovarian cancer risk, HR = 1.04 per 5-kg/mP = 0.01), with a stronger association for premenopausal women  compared with postmenopausal women .Similar to BMI at the date of questionnaire completion, we detected a significant interaction of BMI in young adulthood and menopausal status . BMI-GS was positively associated with ovarian cancer risk in premenopausal women  but not in postmenopausal women . BMI-GS also tended to be more associated with non-serous  than serous tumours .In the entire consortium, the BMI-GS had a nonsignificant positive association with ovarian cancer risk with a HR = 1.10 per 5-kg/mI2 = 15.9%), indicating a low likelihood of pleiotropic associations. Using the two-stage residual inclusion approach, we found a generally similar association .We found similar results when we statistically combined the associations of the 93 BMI-associated variants, with an overall HR = 1.12, 95% CI: 0.86–1.46. Heterogeneity was low  and menopausal status on ovarian cancer risk, with increasing BMI associated with increased risk in premenopausal but not in postmenopausal women.Using data from a large international consortium of BRCA1 and BRCA2 mutation carriers is corroborated by several prior studies in the general population.33 One MR analysis using 77 BMI-associated SNPs, conducted in the general population, found that each 1-standard deviation (SD) increment in genetically-predicted adult BMI corresponded to an odds ratio (OR) of 1.35 (95% CI: 1.05–1.72).34 We found that 5-kg/m2 (about 1 SD) increment in genetically predicted BMI was associated with an HR = 1.10 (95% CI: 0.86–1.42) in mutation carriers. However, the association of BMI with ovarian cancer risk is likely to vary by menopausal status. In the general population, significant differential association of BMI with ovarian cancer risk by menopausal status has been found in some studies36 but not in others.37 A pooled analysis of 47 epidemiologic studies with 25,157 ovarian cancer cases showed that the relative risk per 5-kg/m2 increase in BMI was 1.12 (95% CI: 1.07–1.17) in premenopausal women and 1.08 (95% CI: 1.04–1.12) in postmenopausal women.12 The largest single cohort study, with 3686 ovarian cancer cases, found that the HR per 5-kg/m2 increase in BMI was 1.21 (99% CI: 1.09–1.33) in premenopausal and 1.07 (99% CI: 1.02–1.12) in postmenopausal women.15 An MR analysis conducted in the general population also observed stronger associations for non-high-grade serous carcinomas in premenopausal women  compared with postmenopausal hormone replacement therapy (HRT) users  and postmenopausal HRT non-users , though no formal statistical tests examining heterogeneity were performed.14 Similarly, we found in BRCA1/2 mutation carriers that 5-kg/m2 increment in genetically predicted BMI was associated with an HR = 1.59 (95% CI: 1.08–2.33) for premenopausal ovarian cancer and an HR = 0.80 (95% CI: 0.58-1.11) for postmenopausal ovarian cancer. Studies that have not demonstrated significant variation by menopausal status tended to show that the positive association between BMI and ovarian cancer risk was primarily among those who had never used HRT.12 Taken together, our results and previous literature are suggestive that higher BMI may increase ovarian cancer risk in premenopausal women but not in postmenopausal women.Our finding of a positive association between BMI and overall ovarian cancer risk in 2, 95% CI: 1.11–1.23) or mucinous ovarian cancer  but no association with serous ovarian cancer .16 A more recent MR analysis in the same consortium using a genetic score comprised of 87 SNPs showed that a genetically predicted BMI had a stronger association with endometrioid  or mucinous ovarian cancer  than high-grade serous cancer , though the 95% CIs for these estimates were largely overlapping.14 Consistent with findings in the general population, our study in BRCA1/2 mutation carriers showed that BMI was positively associated with non-serous ovarian cancer , of which endometrioid is a major subtype. Of note, obesity is an established risk factor for endometrial cancer.38 However, subsequent studies with greater number of cases of different ovarian cancer subtypes are needed to assess whether the effect of obesity truly differs by tumour subtype.In addition, several studies that had sufficient numbers of cases to evaluate the relationship between BMI and ovarian cancer risk by histologic subtype have shown significant heterogeneity. Observational studies in the Ovarian Cancer Cohort Consortium found stronger associations between BMI and endometrioid  in ovarian cancer risk,12 and 5-cm increment in genetically predicted height was associated with a 6% (95% CI: 1–11%) increase in ovarian cancer risk.39 The associations for observed height did not differ significantly between ovarian histological types,12 while genetically predicted height had a stronger association with clear cell  or low-grade/borderline serous ovarian cancers  compared to high-grade serous .39 We did not find statistically significant heterogeneity by histology in our study of mutation carriers, though point estimates varied across histology.Our finding of a nonsignificant positive association between height and ovarian cancer risk is also consistent with prior epidemiological studies in the general population.41 The association of PCOS with ovarian cancer risk was mainly confined to premenopausal women.42 Some studies have suggested that BRCA1/2 mutation carriers may have subclinical ovarian insufficiency, which could mediate the relationship between obesity-related infertility and increased ovarian cancer risk.43 Obesity itself also creates a proinflammatory state and adipocyte-secreted inflammatory markers have been implicated in ovarian cancer development.44 Circulating levels of oestradiol, androgen, and progesterone have also been implicated in the risk of ovarian cancer.46 One study in BRCA1/2 mutation carriers showed higher oestradiol levels during each menstrual cycle compared with non-carriers, supporting the potential role of sex hormones in ovarian tumorigenesis in this population.47 Obese premenopausal women tend to have lower circulating levels of progesterone compared with normal weight women.48 Higher progesterone levels may reduce ovarian cancer risk, through upregulation of p53, leading to tumour cell apoptosis.51 Taken together, these pathways may explain the association of higher BMI with premenopausal ovarian cancer risk. In addition, height has been associated with higher levels of circulating insulin-like growth factor-1 (IGF-1),53 a pathway that has been implicated in tumour transformation and may exert antiapoptotic and mitogenic effects.55 Moreover, BRCA1 may directly interact with the IGF-1 pathway to mediate cancer risk.56Several biological mechanisms potentially explain the associations observed in our study. Overweight/obese women are more likely to have anovulatory cycles and fertility issues, particularly when caused by polycystic ovarian syndrome (PCOS), and thus have an increased risk of ovarian cancer.57 found a substantial number of new genetic loci related to height and BMI, increasing the amount of variation that could be explained for these two traits to 24.6% and 6.0%, respectively, although the variation that could be explained when examining these SNPs in a validation cohort was 14.0% and 2.3%. This is comparable to the amount of variation that could be explained using the set of genetic variants in our study. Including these additional SNPs may be able to improve the precision of our estimates for both height and BMI. Moreover, the inclusion of rare variants to strengthen the height and BMI genetic instruments should also be considered in future studies.58 Our study did not explicitly examine whether adding height or BMI  to existing polygenic risk scores for ovarian cancer could further refine risk prediction. Histology was only available in a subset of ovarian cancer patients, which limits our capacity to understand subtype-specific effects of BMI and height. Our study only included women of European ancestry, which may preclude generalisation to women of other racial/ethnic groups.Our study has several strengths, including large sample size, genetic scores utilising most identified height and BMI variants, several MR methods, and consistent findings between observed and genetically predicted phenotypes. Several limitations of our study should be considered. First, even with a large sample size, the CIs for most risk estimates were wide, which limits inferences about causation. While both the height- and BMI-GS were clearly associated with their respective traits, they were only able to explain 13.4% and 2.6% of the variation, respectively. This reduced the statistical precision of our risk estimates. During the preparation of our manuscript, a new genome-wide meta-analysisBRCA1/2 carriers, possibly more so for premenopausal women. BMI could be used to identify premenopausal women at elevated risk of ovarian cancer. Our finding of a stronger association between BMI and non-serous ovarian cancer warrants confirmation in future studies.In summary, our study suggests that higher BMI may be causally associated with ovarian cancer risk in Supplementary Materials


Statins have demonstrated antineoplastic effects in breast cancer cell lines, particularly in oestrogen receptor (ER)-negative cell lines. However, epidemiological studies have not supported a preventive effect of statin use against breast cancer. Therefore, we examined the association between statin use and contralateral breast cancer (CBC) risk among women with breast cancer.We identified 52,723 women with non-metastatic breast cancer during 1996–2012 from the Danish Breast Cancer Group database. We defined time-varying post-diagnosis statin use as minimum two prescriptions lagged by 1 year. Cox regression analyses were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for CBC associated with statin use.Statin use was associated with a lower CBC risk . The inverse association was strongest for long-term use overall , although the HR specifically for long-term consistent use and high-intensity use approached unity. Among ER-negative breast cancer patients, statin use was associated with a CBC risk reduction .We found some indication that statins reduce the risk of CBC. Further evaluations are needed to disentangle the equivocal results for long-term use and to establish if ER-negative breast cancer patients may benefit most from statin use. However, women who have developed breast cancer have proven susceptibility to the disease, and preventive measures against breast cancer may be more pronounced in such a high risk population. A study based on the Danish Breast Cancer Group (DBCG) and the nationwide Danish Prescription Registry reported a 46% reduced risk of contralateral breast cancer (CBC) associated with use of simvastatin, a lipophilic statin, up to 10 years after primary breast cancer diagnosis.We hypothesise that statin use reduces CBC risk among women with breast cancer, and that the protective effect is most pronounced in women with an ER-negative first breast cancer.8 The DBCG database became nationwide in 1977 and includes detailed clinical information on the vast majority of patients , had no record of laterality of the initial breast cancer (N = 838), or had synchronous (N = 1 447) or metastatic disease (N = 498) at diagnosis. In addition, by linkage to the Danish Cancer Registry,10 we excluded patients who had a history of cancer (except non-melanoma skin cancer) prior to or within 1 year after the primary breast cancer (N = 3770). Finally, we excluded women who received mastectomy of the contralateral breast (N = 748) or developed cancer in the contralateral or same breast within the first year after the first breast cancer diagnosis (N = 234), and women who died or emigrated during this period (N = 1229). The final cohort comprised 52,723 breast cancer patients who were alive and at risk of CBC 1 year after the diagnosis  was consecutively estimated during follow-up as the cumulative number of DDDs divided by the number of days between the first and the latest statin prescription and classified as <1 DDD/day or >=1 DDD/day. Finally, we categorised subtypes of statins according to solubility , but used as a censoring variable.We used a previously established nationwide database on CBCs derived from the Danish Cancer Registry.14 We lagged the date of mastectomy by 30 days to ensure the procedure was prophylactic. Information on death and emigration was obtained from the Danish Civil Registration System.15Follow-up for CBC started 1 year after the first breast cancer diagnosis (baseline) and continued until CBC, other cancer diagnosis (except non-melanoma skin cancer), ipsilateral breast cancer, prophylactic mastectomy of the contralateral breast, death, emigration or end of 2013, whichever came first. Contralateral mastectomy see , Table 116 We used the allocated treatment as adjustment variable in the analyses. Information on diabetes and alcohol- or tobacco-related diseases (yes/no) from 10 years prior to 1 year after the primary breast cancer was retrieved from the Danish National Patient Register.14 We also obtained information on use of prescription drugs from the National Prescription Registry, including pre-diagnosis hormone replacement therapy (>2 prescriptions) and post-diagnosis use (>2 prescriptions) of aspirin, bisphosphonates, metformin and digoxin. The 17 we retrieved information on the highest achieved educational level at primary breast cancer diagnosis .Information on potential confounding factors was retrieved from data available in the nationwide registries in Denmark. From DBCG, we included information on the primary breast cancer diagnosis: age (through a restricted cubic spline), date of breast cancer diagnosis (1996–2000/2001–2004/2005–2008/2009–2012), lobular histology (yes/no), and treatment  and 95% confidence intervals (CIs) for risk of CBC associated with statin use. The fully adjusted model included the covariates defined above and the presented results in the text are from these models. Time since baseline was used as the underlying time scale. In the main analyses, we evaluated the association between post-diagnosis use of statins and patterns of statin use  and type of statins as time-varying categorical variables compared to non-use. Effect measure modification was evaluated by stratified analyses according to information from DBCG on ER status of the primary breast cancer. Moreover, we analysed risk of ER-positive and ER-negative CBC associated with statin use by censoring at date of a non ER-positive and non ER-negative CBC, respectively. We repeated the main analyses restricting statin exposure to (1) lipophilic statins only or (2) simvastatin only  no use before or after first breast cancer diagnosis (reference), (2) use before the diagnosis, (3) use solely after the first breast cancer diagnosis, and (4) use both before and after the diagnosis. This analysis was restricted to women diagnosed between 1997 and 2012 to allow a pre-diagnosis exposure window of at least 2 years.We performed two pre-defined sensitivity analyses. First, we changed the definition of statin use to one prescription in the main analyses. Second, we examined the association between statin use (≥2 prescriptions) and CBC risk using a fixed exposure period of 1 year following the first breast cancer diagnosis.N = 710) were classified as premenopausal if younger than 50 years at diagnosis and postmenopausal if older than 50 years at diagnosis). In addition, we calculated a yearly updated propensity score using a logistic regression model to estimate the probability of being statin user during follow-up (time-varying) or the first year after breast cancer diagnosis (time-fixed). In the propensity model we included the same covariates as in the fully adjusted model as well as menopausal status, lymph node status (positive/negative/unknown) and ER status (positive/negative/unknown) at first breast cancer diagnosis.18 In the Cox model, the propensity score was included through a restricted cubic spline together with age at first breast cancer and statin use (ever use/non-use).In post hoc sensitivity analyses, we also adjusted for menopausal status  at first breast cancer diagnosis .19 using the survival package,20 applying a 5% significance level and two-sided alternatives.All analyses were performed in R version 3.2.321 Furthermore, statin users had a higher prevalence of diabetes, aspirin and metformin use, and shorter education compared with non-users.During the first year following the primary breast cancer, 5481 patients filled two or more statin prescriptions . Post-diagnosis statin use was associated with a slightly reduced risk of CBC  (Table >5 years), whereas the association with shorter duration of statin use was close to unity (<5 years)  (Table >5 years), low intensity ( < 1 DDD/day) statin use , whereas no apparent inverse association emerged for long-term, high-intensity (>=1 DDD/day) statin use . In addition, we observed a reduced risk for CBC for irregular use of statins , but not for consistent use . In a post hoc analysis, we found no difference in CBC risk when consistent statin use was stratified into short-term use  and long-term use . The majority of patients used the highly lipophilic statin, simvastatin (71%) and a slightly reduced risk of CBC was seen for these users . Use of hydrophilic statins was associated with a statistically insignificant increased risk of CBC , however, use of these agents were rare and the number of CBC was small. When restricting the analyses on patterns of use to lipophilic statins or simvastatin alone, the HRs remained unaltered (data not shown).We observed a reduced risk for CBC  associated with post-diagnosis long-term use (1) Table . StratifAmong women with ER-negative primary breast cancer, we observed a reduced risk of CBC  associated with ever post-diagnosis statin use Table , whereasAmong patients diagnosed between 1997 and 2012, pre-diagnosis statin use was associated with a neutral HR for CBC compared with never-use  Table , whereasThe sensitivity analysis defining statin use as ≥1 prescription showed no major change in the HR for overall post-diagnosis statin use . The analysis applying a fixed exposure period within the first year following the primary breast cancer yielded a HR of 0.76 (95% CI = 0.58–1.00).In post hoc sensitivity analyses, we found no change in the risk estimates when adding menopausal status at first breast cancer diagnosis as a confounder. Finally, adjusting for the propensity of being statin user yielded virtually the same results as in the fully adjusted models.The analyses for competing events showed largely the same pattern as for CBC risk estimates, i.e., use of statins was associated with a reduced risk of the competing events.In this population-based cohort study of 52,723 breast cancer patients, we found a tendency towards a slightly reduced risk of CBC associated with ever and current statin use and a substantial reduction in CBC risk with long-term statin use. Somewhat puzzling, we observed CBC risk reductions associated with long-term statin use of low intensity or irregular use, but not with long-term high intensity or consistent statin use. A substantial reduction in CBC risk with statin use was seen among patients with ER-negative primary breast cancer.7 of 18,769 breast cancer patients from DBCG diagnosed during 1996–2003, thus overlapping with our study population, reported a reduction in CBC risk associated with the most commonly used lipophilic statin, simvastatin . That association was based on 520 women with CBC within 10 years of their first breast cancer. A more recent, but smaller, cohort study from the United States22 had insufficient power to allow a meaningful conclusion on CBC risk. Our study was larger than previous studies and had more detailed information on statin type, timing and patterns of statin use, as well as on ER status of breast tumours.A Danish cohort study2 Similar to our study, a meta-analysis of 10 studies evaluating breast cancer risk according to drug solubility has reported slight risk reductions associated with the highly lipophilic statin, simvastatin.6 Thus, so far there is a suggestion from this meta-analysis and the previous Danish study7 as well as our study that simvastatin use is associated with a decreased breast cancer risk.Lipophilic statins have been suggested to possess the strongest antineoplastic effects due to their ability to cross cell membranes.6 This previous study is compatible with our finding of a reduced CBC risk associated with long-term use for more than 5 years. However, when we combined long-term use with the highest level of daily dose or with use without exposure gaps to identify the women who would be most heavily exposed to statins, we did not observe a pattern supporting a duration- or dose-response relationship. However, the results were based on relatively small numbers. Additional studies are needed to explore these equivocalities in our results, e.g. to investigate the dose level required to achieve antineoplastic effects of statins in humans.Long-term use of statins (>5 years) was suggested to be associated with a reduced risk of breast cancer in a meta-analysis based on 8 studies.24 Besides, women with ER-negative breast cancer are at increased risk of CBC compared with women diagnosed with the ER-positive phenotype, and in particular ER-negative CBC.26 Previous epidemiological studies of either lipophilic statin use specifically28 or any statin type31 have found no evidence of a differential effect by ER status. Our study suggested a reduced risk of CBC associated with statin use in patients with ER-negative primary breast cancer. This finding could imply an additional benefit of post-diagnosis statin use in addition to the growing evidence of reduced mortality35 and reduced risk of recurrences36 associated with statin use after breast cancer. Therefore, our results deserve to be evaluated further.Preventive measures for ER-negative breast cancer are highly warranted.37The strengths of our study included comprehensive nationwide data from a clinical database (DBCG), ensuring an unselected study population of breast cancer patients with high case validity. This was supplemented by high quality data from nationwide demographic and health registries ensuring virtually complete follow-up. Prescription data are not subject to recall bias, and statins are in Denmark available only by prescription. Large observational studies with long-term follow-up are valuable when investigating the influence of statin use on CBC risk, given the difficulties to implement a randomised trial among breast cancer patients with sufficient power to detect rare and long-term adverse outcomes, such as CBCs.38 Statin users were more likely to have shorter education and comorbidities than non-users, which do not support that the overall group of statin users in our study had a heathier lifestyle. Nevertheless, we cannot rule out that long-term low intensity statin use might reflect adherence to a healthier lifestyle. In all instances, the analyses were adjusted for education and comorbidity that are indicators of lifestyle.42 Our results suggested no major difference in overall risk estimates according to timing of statin use indicating that prevalent user bias may not be a major concern. Further analyses on patterns of statin use and ER status restricted to ‘new users’ are not likely to provide additional information on the issue of prevalent user bias due to limited statistical precision. Patients with recurrence following primary breast cancer may be more unlikely to be registered with a new primary tumour in the contralateral breast than those without recurrence. Since statin users tend to have fewer recurrences, this may have biased the association toward the null. In observational studies of statins and cancer risk reverse causality might impact results if patients undiagnosed with cancer experience weight loss and improved lipid profiles and consequently do not use statins. However, this is unlikely to have affected our results to any great extent because general or non-breast symptoms are uncommon in patients with primary breast cancer.43 In addition, we censored patients with distant metastases at CBC diagnosis and other cancer diagnoses for whom disease symptoms potentially could have affected their use of statins. Finally, we cannot exclude the possibility of important residual confounding from unmeasured variables associated with both statin use and CBC risk.Our study also had some limitations. We had no information on compliance to statins and other drug use. We attempted to minimise exposure misclassification by defining drug use as at least two prescriptions filled on separate dates. In addition, adherence to statins in Denmark has been reported to be high (>84%).In conclusion, we found some support of a reduced risk of CBC associated with statin use among breast cancer patients. Further studies are required to clarify the equivocal findings according to pattern of statin use, notably for long-term use, and to determine if statin use could be particularly useful for women with breast cancer of the ER-negative phenotype.Supplemental material


The objective of this article is to review the basis supporting the usefulness of melatonin as an adjuvant therapy for breast cancer (BC) prevention in several groups of individuals at high risk for this disease. Melatonin, as a result of its antiestrogenic and antioxidant properties, as well as its ability to improve the efficacy and reduce the side effects of conventional antiestrogens, could safely be associated with the antiestrogenic drugs presently in use. In individuals at risk of BC due to night shift work, the light-induced inhibition of melatonin secretion, with the consequent loss of its antiestrogenic effects, would be countered by administering this neurohormone. BC risk from exposure to metalloestrogens, such as cadmium, could be treated with melatonin supplements to individuals at risk of BC due to exposure to this xenoestrogen. The BC risk related to obesity may be reduced by melatonin which decrease body fat mass, inhibits the enhanced aromatase expression in obese women, increases adiponectin secretion, counteracts the oncogenic effects of elevated concentrations of leptin; and decreases blood glucose levels and insulin resistance. Despite compelling experimental evidence of melatonin’s oncostatic actions being susceptible to lowering BC risk, there is still a paucity of clinical trials focused on this subject. Breast cancer is one of the most common neoplasias in women, with about 1.7 million new cases diagnosed worldwide in 2012, representing about 25% of all cancer cases in women, and is the second leading cause of cancer deaths in developed countries . As a co prevention of breast radiation dermatitis [Melatonin is an indoleamine secreted mainly by the pineal gland with circadian rhythmicity. This molecule exerts regulatory actions on multiple physiological functions. For example, melatonin is involved in the modulation of the neuroendocrine reproductive axis, the metabolism of lipids and carbohydrates, the rhythm of body temperature, the sleep/wake rhythm, the oxidative status, etc. ,7,8,9. Frmatitis  or to dermatitis . It is crmatitis , as wellrmatitis , togethermatitis ,18. CurrThe aim of this article is to review the evidence that supports the usefulness of melatonin, not for BC treatment, but rather as an adjuvant preventive therapy for BC in several groups of individuals at high risk for this disease. In this review we will attempt to demonstrate that there is ample evidence which suggests that melatonin could be an efficient complement in at least the following situations: (1) where the reduction of BC risk is based on treatment with antiestrogenic drugs; (2) when the risk of BC depends on environmental factors such as chronodisruption due to exposure to light at night (i.e. night shift work) or the exposure to contaminants such as xenoestrogens and, (3) in BC risk cases related to obesity.About 70% of all breast cancers express estrogen-receptors (ER+) and circulating concentrations of estrogens are positively associated with an increased risk of BC in premenopausal women . The parWhile the main source of estrogens in premenopausal women is the ovaries, in postmenopausal women adrenal androgens and sulfated estrogens are the primary circulating steroids, and these steroids are converted into active estrogens by enzymatic processes in the mammary tissue. In the last 20 years, two main families of drugs which are able to interact with the synthesis and actions of the estrogens were developed and are now used for the prevention and treatment of ER+ BC. Selective estrogen receptor modulators (SERMs) are drugs that are able to bind to the ER and act as estrogen antagonists in the uterus and breast. Tamoxifen, a first generation SERM, is probably the most widely used drug in BC prevention. The results of different clinical trials in women classified as having a high risk for BC showed that treatment with tamoxifen (20 mg/day) for 5 years significantly reduced the incidence of ER+ BC, but not of ER− tumors ,31. FlusA second family of antiestrogenic drugs includes the selective estrogen enzyme modulators (SEEMs), that is to say, drugs that do not bind to the ER but instead modulates the activity of the enzymes involved in the conversion of androgens into estrogens, as well as those involved in the interconversion between inactive (conjugated) and active (unconjugated) steroids. Exemestrane and anastrozole are drugs belonging to the SEEM family, and both have antiaromatase properties. Their efficacy in reducing the risk of BC in postmenopausal women has been demonstrated in different clinical trials . Their mInterestingly, melatonin acts as a SEEM and inhibits the expression and activity of P450 aromatase, type I 17β-hydroxysteroid dehydrogenase and estrogen sulfatase, that is to say, the expression of the enzymes responsible for the formation of biologically active estrogens from steroids (androgens and estrogens) with low biological activity . FurtherIn addition to its simultaneous properties functioning as both a SEEM and a SERM, experimental data has also revealed that melatonin increases the sensitivity of MCF-7 cells to the effects of antiestrogens such as tamoxifen , and thaN-desmethyl-4-hydroxytamoxifen-melatonin showed anticancer effects without the uterine hyperproliferation observed after treatment with tamoxifen alone. These results have not yet been published in ordinary scientific journals.Furthermore, melatonin could be also useful for reducing or suppressing some of the side effects of conventional antiestrogens . In thisInterestingly, the possible association of melatonin with antiaromatases could reduce the risk of osteoporosis described with treatment with this family of drugs. Melatonin promotes osteoblast proliferation and the synthesis of osteoprotegerin, a member of the tumor necrosis factor receptor (TNFR) superfamily. This protein inhibits the differentiation of osteoclasts by preventing the binding of osteoclast differentiation factor (ODF) to receptor activator of NK-κB ligand (RANK) on the differentiating osteoclasts. In this way, melatonin could cause an inhibition of bone resorption and an increase in bone mass ,53,54,55A meta-analysis of 51 epidemiological studies comprising more than 150.000 women, carried out by the Collaborative Group on Hormonal Factors in Breast Cancer  concludeIn conclusion, the above-mentioned data strongly supports the possible benefits of the association of melatonin with conventional antiestrogens as well as HRT to reduce the risk of BC, and clinical trials to analyze the efficiency of these cotreatments are encouraged.The “classical” risk factors for breast cancer, that is to say, genetic mutations, reproductive history, obesity, alcohol consumption, radiation and sedentary lifestyle do not explain all the potential situations of increased risk of mammary carcinogenesis. The link between BC risk and environmental factors is a subject of growing relevance . There iCircadian rhythm disruption induces alterations in one hallmark of cancer, cell division, thus contributing to cancer progression, and the pharmacological modulation of proteins related to clock genes is being considered as a possible strategy for cancer treatment ,65. ChroThat LAN increases the rate of growth of mammary tumors has been solidly established in experiments carried out in rodents with chemically induced tumors or xenografts of cancer cells ,67. FurtThe association between shift work including night work and the increased risk of different kinds of cancer is supported by numerous studies ,69,70,71The two most widely accepted explanations for the biological effects of LAN in elevated BC risk are: the light-induced inhibition of melatonin secretion, with the subsequent loss of the SEEM and SERM effects of this neurohormone; and alterations to the circadian system (chronodisruption) induced by exposure to nocturnal light ,82,83,84Regarding the influence of decreased melatonin secretion, a relationship between low plasma melatonin concentration and breast cancer was described as early as 1978 by Cohen et al. ; women wCLOCK gene in the development of breast cancer in shift workers has been proposed [CLOCK, BMAL1, BMAL2 and NPAS2 clock genes [The cell cycle is controlled by the circadian system, and the progression through its different stages occurs at specific times of the night/day cycle. Although the body’s central clock, situated in the suprachiasmatic nucleus of the hypothalamus is responsible for the synchronization of the entire circadian system, peripheral clocks located in almost all cells assume important regulatory functions such as control of the cell cycle. The coupling between the cellular clocks and the cell cycle is the key to explaining the relationship between chronodisruption and cancer ,90; the proposed , and epick genes ,97.The administration of melatonin (1–10 mg/day) to night shift workers has been widely assayed as a way to ameliorate the body’s adaptation to nocturnal work or to lessen insomnia during the day ,99,100. Among the environmental factors with possible incidence in BC risk, the role of chemical contaminants is a matter of discussion, although there is general agreement that environmental estrogen-like compounds (xenoestrogens) could be related to the onset and development of BC . CurrentCd is naturally present in soils, sediments, seawater, plants, and animals and is a food-chain contaminant. An individual’s environmental exposure to Cd depends on dietary sources but also from tobacco smoke (a pack of cigarettes contains about 2–4 μg of Cd) . OccupatAlthough the kidneys are the organs most affected by Cd exposure, epidemiological studies have demonstrated that this metal can increase the risk of BC ,112,113.There are two basic explanations for the effects of Cd on the mammary gland. One, is related to the estrogenic effects of this metal. Cd increases the in vitro proliferation of ER+ breast cancer cells as well as the expression of estrogen-regulated genes, and increases signaling by ERK1/2 and Akt pathways ,125. In Melatonin exerts remarkable actions against the estrogenic effect of Cd. In MCF-7 human BC cells, melatonin prevents cell proliferation by acting as a specific inhibitor of Cd-induced ERα-mediated transcription in both, estrogen response elements and AP1-containing promoters . FurtherEpidemiologic studies included in the Women’s Health Initiative Observational Study have concluded that generalized obesity represents an important risk factor for breast cancer among postmenopausal women who have never received HRT, in comparison with slimmer women ,136,137.2) participants were randomly treated with melatonin (10 mg/day) or placebo for 30 days, combined with caloric restriction. A significant reduction in BW was observed in obese patients treated with melatonin in comparison with those receiving placebo [Obviously, the prevention of obesity is the first way to avoid the BC risk related to being overweight. Melatonin should be considered as a tool for obesity management. Various experiments carried out in rats have demonstrated that chronic melatonin consumption prevents the effects of obesogenic diets . Further placebo . Interes placebo . Sleep d placebo ,148,149. placebo ,151. TheIn postmenopausal women ovarian synthesis of estrogens is replaced by local synthesis in peripheral tissues including mammary glands. The expression of aromatase, the enzyme involved in the synthesis of estrogens via aromatization of the adrenal androgens, is present in mammary adipose tissue of normal and tumoral glands . One of Being overweight or obese is a result of an excessive accumulation of fat in white adipose tissue (WAT) with hyperplasia and hypertrophy of adipocytes, and the development of a state of chronic inflammation of the WAT. In addition to the storing triglycerides, WAT is the source of bioactive molecules globally termed as adipokines, which have been correlated with the development of BC ,158. AmoAdiponectin, whose levels are inversely correlated with adiposity, exerts direct growth-inhibitory effects on tumor cells by inhibiting cell proliferation and angiogenesis, and upregulating apoptosis . The levRegarding leptin, its concentration is increased in the obese, reflecting the amount of fat in the body. In mammary glands, leptin is synthesized in preadipocytes, adipocytes and epithelial cells . This hoObese persons become insulin resistant (IR), as a part of the metabolic syndrome (MS). This IR is due to the effects of some of the adipokines such as tumor necrosis alpha, interleukine-6 or resistine . AnotherRecently, it has been shown that the oral antidiabetic drug metformin, used in the treatment of type 2 diabetes, has in vitro antiproliferative effects in different breast cancer cells lines , and preIn this review we have summarized the evidence in favor of the possible use of melatonin as an adjuvant therapy for individuals with risk factors for BC. One conclusion is that experimental studies provide results which support the value of melatonin as an oncostatic drug for reducing the risk of ER+ breast cancer. The antiestrogenic effects of melatonin (as SEEM and SERM); the additive results of its association with conventional antiestrogenic drugs , improving their positive effects while mitigating or preventing their unwanted side effects; its antioxidant properties; its effects in obesity and associated metabolic disorders; and its properties as a chronobiotic agent, countering the effects of exposure to LAN, these are all arguments that, together with its lack of toxicity, strongly recommend the realization of clinical trials to evaluate whether this basic knowledge is applicable to programs for reduction of BC risk.


Background: Association between metabolic syndrome (MetS) and incidence of breast cancer remains to be validated. Moreover, whether menopausal status of the women affects this association is unclear. A meta-analysis was performed to summarize the association between MetS and breast cancer risk.Methods: Follow-up studies were identified by search of PubMed and Embase databases published until May 26, 2019. A random-effect model or fixed-effect model was applied to pool the results according to the heterogeneity. Subgroup analyses according to the menopausal status, ethnic groups, cancer histopathological features, and study design characteristics.Results: Overall, 17 follow-up studies with 602,195 women and 15,945 cases of breast cancer were included. Results of meta-analysis showed that MetS defined by the revised National Cholesterol Education Program's Adults Treatment Panel III criteria was associated with significantly increased risk for breast cancer incidence . Subgroup analyses showed that MetS was associated with significantly increased risk of breast cancer in postmenopausal women , but significantly reduced breast cancer risk in premenopausal women . Further analyses showed that the association between MetS and increased risk of breast cancer were mainly evidenced from studies including Caucasian and Asian women, reporting invasive breast cancer, and of retrospective design.Conclusions: Menopausal status may affect the association between MetS and breast cancer incidence. Postmenopausal women with Mets are associated with increased risk of breast cancer. Breast cancer is one of the most common malignancies in women globally, with ~1.4 million new cases diagnosed annually . DespiteThe meta-analysis was designed and performed in accordance with the MOOSE   and CochElectronic databases of PubMed and Embase were systematically searched using the combination of the following terms: (1) “metabolic syndrome” OR “insulin resistance syndrome” OR “syndrome X”; (2) “cancer” OR “tumor” OR “neoplasm” OR “carcinoma”; and (3) “cohort” OR “prospective” OR “retrospective” OR “nested case-control” OR “follow-up” OR “followed.” We applied this extensive search strategy to avoid missing of potentially related studies. The search was limited to studies published in English. The reference lists of original and review articles were also analyzed manually. The final literature search was performed on May 26, 2019.Studies were included if they met the following criteria: (1) published as full-length article in English; (2) designed as longitudinal follow-up studies with the minimal follow-up duration of 1 year; (3) included women without breast cancer at baseline; (4) women with MetS were identified as exposure of interest at baseline; (5) women without MetS at baseline were included as controls; (6) documented the incidence of breast cancer during follow-up; and (7) reported the adjusted risk ratios  and their corresponding 95% confidence intervals (CIs). Definitions of MetS were consistent with that was applied in the original studies. Reviews, editorials, preclinical studies, and non-cohort studies were excluded.Literature search, data extraction, and study quality assessment were independently performed by two authors according to the predefined inclusion criteria. If inconsistencies occurred, discussion with the corresponding author was suggested to resolve these issues. The following data were extracted: (1) name of the first author, publication year, study location, and study design; (2) characteristics and numbers of the women, ethnic groups, criteria for the diagnosis of MetS, and follow-up period; and (3) number of cases with breast cancer during follow-up, and variables adjusted when presenting the RRs. The quality of each study was evaluated using the Newcastle-Ottawa Scale (NOS) . This scI2 statistic was also calculated. A significant heterogeneity was considered if I2 > 50%. A random effect model was used to pool the results if significant heterogeneity was found; otherwise a fixed effect model was applied. Sensitivity analyses, by omitting one study at a time, were performed to evaluate the potential influence of certain study on the outcome of the meta-analysis  from each study was logarithmically transformed . The Cocanalysis . To evalanalysis . Potentianalysis . The RevThe flowchart of database search was shown in Overall, this meta-analysis included 17 follow-up studies –32 incluI2 = 79%). Pooled results with a random-effect model showed that women with MetS were associated with significantly increased risk for breast cancer incidence , suggesting the robustness of the finding. Meta-analysis with two studies , but with significantly reduced risk of breast cancer in premenopausal women , a trend of increased risk of breast cancer in Asian women , but unchanged risk of breast cancer in African women , but the association was not significant for breast cancer in situ , but not significant in prospective cohort studies . Publication bias for the meta-analysis of IDF defined MetS and breast cancer risk was difficult to estimate since only two studies were included.The funnel plots for the association between MetS diagnosed by the revised NCEP-ATP III and breast cancer risk were symmetry on visual inspection , suggestIn this meta-analysis of longitudinal follow-up studies, we found that women with MetS were associated with significantly increased incidence of breast cancer during follow-up. Interestingly, stratified analyses showed that MetS was associated with increased risk of breast cancer in postmenopausal women, but with reduced risk of breast cancer in premenopausal women. Stratified analyses also showed that the significant association between MetS and breast risk was mainly driven by studies including Caucasian and Asian women, reporting outcomes of invasive breast cancer, and those of retrospective design. Taken together, results of our study confirmed previous findings that MetS is associated with significantly increased risk of breast cancer in postmenopausal women. Moreover, results of our study suggested that the menopausal status of the women may be an important modifier for the association between MetS and breast cancer risk. Premenopausal women with MetS may be associated with reduced risk of breast cancer.Our study has a few strengths compared to previous meta-analyses of the same topic. Firstly, we included longitudinal follow-up studies only, and case-control studies were excluded from the meta-analysis. This is to control the potential recall and interviewer biases inherited in case-control studies. Secondly, we extracted the most adequately adjusted RRs to reflect a potentially independent association between MetS and breast cancer risk. Thirdly, the numbers of included follow-up studies were relatively large (nineteen datasets from 17 follow-up studies) compared with those previous published meta-analyses , which allowed us to analyze the potential study characteristics on the association between MetS and breast cancer incidence. Finally, our subgroup analyses for the first time showed that menopausal status of the women may be an important modifier for the association between MetS and breast cancer risk, and premenopausal women with MetS may be associated with reduced risk of breast cancer.The potential mechanisms underlying the independent association between MetS and increased risk of breast cancer in postmenopausal women are likely to be multifactorial. Pervious experimental studies showed that insulin resistance and chronic inflammation are the characterized pathophysiological features in MetS people . Insulin2 increase of BMI was associated with 12% increased risk of breast cancer in postmenopausal women, but 8% reduced risk in premenopausal women  and breast cancer risk, the authors found that every 5 kg/mal women . Similaral women , but 9% al women . The divl biases , resultsl biases .in situ) should be confirmed in future studies since limited datasets were available. Finally, as mentioned above, breast cancer is a heterogeneous disease with different histopathological features. The association between MetS and different subtypes of breast cancer should be evaluated in the future.Our study has limitations, which should be considered when interpreting the results. Firstly, as a nature of meta-analysis of observational studies, we could not exclude other residual confounding factors that may contribute to the association between MetS and breast cancer risk, such as treatments with metformin . SecondlIn conclusion, our updated meta-analysis showed that MetS is associated with significantly increased risk of breast cancer in postmenopausal women. Moreover, menopausal status of the women may be an important modifier for the association between MetS and breast cancer risk, and premenopausal women with MetS may be associated with reduced risk of breast cancer.PL and WW designed the study. PL, TW, and CZ performed database search, data extraction, and quality evaluation. PL, MY, GL, and JH performed data analyses. PL and WW drafted the manuscript. All authors critically revised the manuscript and agreed submission.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Across the African Diaspora, hair is synonymous with identity. As such, Black women use a variety of hair products, which often contain more endocrine-disrupting chemicals than products used by women of other races. An emerging body of research is linking chemicals in hair products to breast cancer, but there is no validated instrument that measures constructs related to hair, identity, and breast health. The objective of this study was to develop and validate the Black Identity, Hair Product Use, and Breast Cancer Scale (BHBS) in a diverse sample of Black women to measure the social and cultural constructs associated with Black women’s hair product use and perceived breast cancer risk.Participants completed a 27-item scale that queried perceptions of identity, hair products, and breast cancer risk. Principal Component Analyses (PCA) were conducted to establish the underlying component structures, and confirmatory factor analysis (CFA) was used to determine model fit.sociocultural perspectives about hair and identity loaded on subscale 1 and accounted for 32% of total variance . Six items assessing perceived breast cancer risk related to hair product use loaded on subscale 2 and accounted for 29% of total variance (α = 0.82 (95% CI = 0.74–0.86). CFA confirmed the two-component structure .Participants (n = 185) were African American (73%), African, and Caribbean Black women (27%) aged 29 to 64. PCA yielded two components that accounted for 61% of total variance. Five items measuring The BHBS is a valid measure of social and cultural constructs associated with Black women’s hair product use and perceived breast cancer risk. This scale is useful for studies that assess cultural norms in the context of breast cancer risk for Black women. Breast cancer remains the second leading cause of death in the United States among women , 2, withOne environmental factor that has been gaining increasing attention in breast cancer research is hair and personal care products –11. A grIn addition, Myers et al.  assessedDespite the mounting evidence of possible health risk, hair products remain popular in the Black community , 11, 18.The literature on Black women’s attitude to their hair offers mixed explanations for the popularity of hair care products in Black communities. Some scholars suggest hair across the African diaspora is synonymous with identity, individuality, and beauty norms , 21. ForThere is a gap in our understanding of how these environmental, sociocultural, and biological factors converge and impact breast cancer risk and outcomes among Black women. Currently, there is no validated scale that measures constructs related to hair, identity, and breast health. Instruments have been developed to measure related but general issues, such as social and personal identity , health This study was part of a broader project that used a mixed method design and community-based participatory research (CBPR) principles to evaluate the association between hair products use and perceived breast cancer risk among Black women in Southern California. The study was conducted in two phases: a qualitative phase followed by a quantitative phase. Findings from the qualitative phase were used to inform quantitative data collection. This design is particularly useful for developing a new scale . The proTo ensure all research activities were within ethical guidelines, an application detailing the project was submitted and approved by the Loma University Institutional Review Board (IRB). Every participant provided written informed consent. All individuals involved with data collection were certified  in research ethics using an IRB approved curriculum developed specifically for CBPR data collection .Recruitment for the broader study took place in two stages. In stage 1, we used purposive sampling to recruit participants (n = 125) who self-identified as African American, African, or Afro-Caribbean. In stage 2, we used snowball and convenience sampling to recruit African American, African, or Afro-Caribbean men (n = 66) and women (n = 211). The social networks of the two community co-principal investigators agencies were used to recruit participants. For both stages, participants were primarily recruited face-to-face at churches, hair salons, community meetings, women’s conferences, hair and education showcases, and other areas where the target population congregated. Also, flyers were posted in these settings and emailed to listservs of the community investigators. For stage 1, participants received $20 in the form of store cards . Participants were not compensated for their participation in stage 2 of the study. For both stages, data were collected in churches, beauty salons, and community meetings.The analysis described in this paper includes only Black women with or without a history of breast cancer (n = 185). Women were excluded from the study if they did not self-identify as African American, African, or Afro-Caribbean.In Phase 1 of the study, we explored the cultural and personal meaning of hair in the Black community. Interview questions were developed by participant type  . QuestioNavigators were trained in basic qualitative and quantitative research approaches including the development of semi-structured interview guides, interviewing skills, the codebook development for qualitative data analysis, and research team trainings on how to use QDA-miner—a qualitative data analysis software  that wasTo achieve triangulation, the navigators used a common semi-structured interview guide adjustedInterviews and focus groups were audio recorded and transcribed verbatim to maintain accuracy. We used QDA-Miner to code and analyze the transcripts using a Grounded Theory approach . FollowiStrongly disagree, Disagree, Agree, and Strongly agree. The 27-item scale discussed here was one component of a larger 42-item survey instrument. Other questions explored respondent’s lifestyle, health behaviors, BC knowledge, demographics, and family medical history. Questions were reviewed for clarity among the research team and pilot tested prior to their use in the final survey.After the themes from the qualitative results were identified, the investigator from the academic institution guided the community navigators in a series of discussions that resulted in the development of questionnaire items. Items were grouped into two categories:1) perceived risk, knowledge, and attitudes about Black hair and breast cancer (8 items); and 2) perceptions about hair and Black culture (19 items). Questions pertaining to perceived risk, knowledge, and attitudes about Black hair and breast cancer included items such as “All Black women should worry about the ingredients in hair products”; and “Because of breast cancer, I intend to watch the ingredients of the products I will use”. Questions pertaining to perceptions about hair and Black culture explored beliefs about Black hair in the workplace, hair product use, and cultural and personal attitudes related to hairstyles. Items included “Hair has a special role in Black culture”; “My hair is a cultural reflection of who I am”; and “I do not care how much I spend on hair products.” For all questions, the Likert scale response options were In Phase 2, navigators used the 42-item questionnaire developed in Phase 1 to collect data in settings previously mentioned. Each questionnaire took approximately 30–45 minutes to complete and the majority (approximately 98%) were completed in person. Those that were not completed in person were submitted electronically or via postal mail. Data were collected from 2015 through 2016.Some high school, High school diploma , Some college, College degree, Graduate degree, and Professional certification . Age was denoted in years. Household income question was: “Please check the range of income that is closest to your own:” with the following response options: Less than $25,000; $26,000-$50,000; $51,000-$75,000; $76,000-$100,000; $100,000-$150,000 and More than $151,000. Insurance status was assessed using the question: “Do you have health insurance?” With response options Yes or No. Birth place was determined using the question: “Were you born in the United States?” With response options Yes or No. The question, “Have you been diagnosed with cancer?” With response options Yes or No, was used to assess diagnosis status. Family history of breast cancer was determined using the question: “Have any of your family members been diagnosed with breast cancer?” With response options Yes or No. The question “Have you ever had a mammogram?” was used to assess participant breast cancer screening history with response options Yes or No. Product use information was obtained using the question “How often do you use the following products?” Product types included wash out conditioner, leave in conditioner, relaxer from salon, do it yourself relaxer, detangler, damaged hair treatment (i.e. hair mayonnaise), do it yourself hair dye kits, and professional hair coloring. Response options included 1) Several times a week, 2) Daily, 3) Several times a month, 4) Several times a year, 5) Used to/stopped using and 6) Never used it. Response options 1–5 were recategorized as Yes for product use and response option 6 was recategorized as No for product use in analyses.Education level was assessed using the question: “What is the highest level of education you have completed?” Response options were: In order to examine the underlying structure and dimensions of identity, hair products use, and perceived breast cancer risk, a Principal Component Analysis (PCA) was conducted using SPSS 24.0 . As thisSeveral criteria were used to examine the number and combination of items in each component, including Horn’s parallel analysis, a scree2 assess overall fit and the discrepancy between the sample and fitted covariance matrices. In addition to the χ2 test, the AIC is compared for each fitted model[Confirmatory factor analyses (CFA) were performed using Mplus software  to deterted model. The AICThe final analytic sample (n = 185) was comprised of 73% African American and 27% Caribbean and African Black women aged 29 to 64 years . ParticiWe examined the factor structure of the 27 items with an aim to better understand the structure and dimensionality of identity, perceived risk, and attitude regarding Black hair and perceived breast cancer risk. According to fit criteria, PCA with Varimax rotation yielded two distinct components that accounted for 61% of the total variance, with 11 of the 27 items loading highly on these two unique components. A parallel analysis also indicated a two-component solution, though 1-component and 3-component solutions were also examined in subsequent CFA. The remThe first component, which consisted of five items representing sociocultural perspective about hair and identity, accounted for 32% of the total variance and demonstrated robust reliability . The second component accounted for an additional 29% of the total variance and consisted of six items that measure perceived breast cancer risk related to hair product use. Cronbach’s alpha for the six-item subscale was 0.82 (CI = 0.74–0.86).2 = 87.225, p-value = <01; AIC = 4219.615; RMSEA = 0.07; CFI = 0.91; TLI = 0.88). Both one-component  and three-component models  were also tested but neither fit the data well according to the fit criteria. The interrelationship between the two confirmed subscales was 0.03 (not significant), demonstrating that each subscale represents a distinct component with no significant intercorrelation at the higher-order level. Given the patterns in both PCA and CFA, we concluded that two subscales were represent in these 11 questions: S1. Sociocultural perspective about hair and identity, and S2. Perceived breast cancer risk related to hair product use.CFA confirmed a two-component model fit the data according to fit statistics for these 11 items  composed of 2 subscales and 11 items, was validated in this study using the methodology utilized in psychometry, 40, 41.Sociocultural perspective about hair and identity, consists of five items representing a sociocultural perspective regarding hair and identity with items like “Q3. In order to be successful in business, it is a necessary for Black women to have their hair straight” and “Q7. Black women feel pressure from their partners to straighten their hair.” This component reflects a distinct dimension that measures hair and identity constructs. Subscale 2, Perceived breast cancer risk related to hair product use is comprised of six items that assess perceptions of risk associated with hair products. Items that loaded highly on this distinct component included questions like “Q24 Because I am concerned about breast cancer, I intend to watch the ingredients of the products I will use” and “Q25 All Black women should worry about the ingredients in hair products”. These reflect a dimension that measures perceived risk and product usage specifically. Both dimensions were found to describe these data, with additional dimensions  leading to degradation in fit. Importantly, the initial PCA model fitting also revealed that more than one component was required to describe the structure of these data. This specifically showed that two components are needed because each reflects a distinct construct that assesses different underlying mechanisms and perceptions.Subscale 1, Furthermore, the topic of hair in the Black community has always represented varying degrees of prominence, ranging from politically charged euphemism to exhortation of African pride –22. TherOverall, this scale acknowledges that both perceived health risk associated with hair products and the sociocultural significance of hair are critical to Black women. Culture is often regarded as the defining element of an individual’s actions that reflects their beliefs, attitudes, and normative behavioral patterns . This stWe hope that the BHBS will help increase our understanding of the interplay between identity, health, and behavioral intentions for Black women, since it provides targeted questions that measure women’s perceptions regarding breast health and identity. With the increasing prominence of research on Black hair and breast health it is critical to take these issues into account. It is also important to note that our women acknowledged both a socio cultural perspective as well as a breast cancer risk perspective in their responses. As the discussion about hair product risk for breast health matures we need to measure and then weigh both, as both clearly affect women’s perspective on the issue. Moreover, since perception precedes and influences behavior, this scale has utility for community-based interventions aimed at promoting healthier hair care alternatives. Through the parent study, for example, stylists and salon owners expressed interest in learning about less harmful products to use on their clients’ hair. This scale can capture data that may help researchers and community based-organizations gauge community members’ willingness to adopt safer products as the field is moving from exploration of risk for breast cancer to community based prevention education.While awareness on the potential hazards of hair and personal care products is increasing, interventions geared towards minimizing risk and exposure should be developed in parallel. It was only 80 years ago (1940s/1950s) that studies from animal experiments, chemical analyses, and epidemiology concluded that cigarettes were the cause of lung cancer . DespiteThere are several limitations that should be considered in the interpretation of findings from this study, including the relatively small group of participants. We also lack participation of a larger group of women with a history of breast cancer. It is recommended for future studies, that women with breast cancer represent a larger percentage of the sample. As many people experience hair loss when receiving treatment for breast cancer , a questWhile the findings of this study are limited by the issues stated above, there is currently no scale examining the relationship between hair, identity and perceived breast cancer risk. As research in the hair-health discipline continues to expand, social/behavioral and basic scientists may benefit from use of this tool.Black women continue to be diagnosed and die from more aggressive forms of breast cancer than White women . There iHowever, all behavior change is complicated and subject to many influences, even in light of emergent scientific insights. As we seek to better understand cultural influences that perpetuate breast cancer disparities, the impact of hair on identity for Black women should also be recognized. Hair is a fundamental component of one’s cultural identity. Our Black Identity, Hair Product Use, and Breast Cancer Scale may provide important insights into the social and behavioral patterns as well as the growing perceptions about risk of Black women in relation to breast cancer prevention and hair product risk. Considering both of these perspectives of women across the African diaspora may yield culturally appropriate strategies that inform interventions about identity, hair product use, and breast cancer risk.