ovarian cancer is a highly fatal gynecologic cancer and the fifth leading cause of cancer mortality in women , with 14,030 deaths occurring in the united states per year ( 1 ) . in korea , ovarian cancer is the ninth leading cause of death with an age - standardized cancer mortality rate of 2.3 per 100,000 women during 2010 ( 2 ) . most cases of ovarian cancer are discovered at an advanced stage and quickly progress , resulting in a poor outcome . the national cancer institute 's surveillance , epidemiology , end results program ( seer ) reported that 68% of ovarian cancer cases diagnosed during 2002 - 2008 presented at the late distant stage with very low 5-yr survival rates ( < 26% ) ( 3 ) . due to the rapid progression and low survival rate , there is usually only a short window of time to evaluate the environmental factors affecting the course of the disease . obesity is a health problem with increasing prevalence and is directly related to various morbidities . among gynecologic cancers , hormone - related cancers such as endometrial cancer and breast cancer are associated with obesity ( 4 ) . recently , there have been some epidemiologic and experimental studies indicating that abdominal adiposity and weight gain increase ovarian cancer risk . they may also increase tumor invasiveness and tumor cell migration in various cancer types ( 5 , 6 ) . however , there have been only a few clinical studies determining the role of obesity in ovarian cancer outcomes . advanced ovarian cancer patients are frequently found in a cachectic state with ascites which may contribute significantly to body weight , but do not counted as real body mass . most patients with ovarian cancer are operative candidates who then receive adjuvant chemotherapy , which can jeopardize their health status . in asian populations , the categorizing standard of obesity is different from that applied to people of western populations , and the incidence of comorbidities is different ( 7 , 8) . therefore , there is still some question regarding whether obesity truly has an adverse effect on the outcome of ovarian cancer among asian patients . the aim of this study was to analyze the relationship between obesity and the survival of patients with advanced epithelial ovarian cancer in korean population . a total of 236 patients who underwent staging laparotomy for advanced ( stage iii and iv ) eoc between january 2000 and february 2009 were included . medical records of 320 patients were retrieved from korea university anam hospital ( 86 patients ) , korea university guro hospital ( 44 patients ) , gachon university gil medical center ( 120 patients ) , kyung hee medical center at gangdong ( 22 patients ) and cha university hospital ( 48 patients ) , korea . all cases were reviewed for height , weight , age , comorbidities and treatment - specific details . patients with a non - epithelial tumor histology , synchronous or metachronous tumors , borderline tumors and early stage ( stage i and ii ) ovarian cancer were excluded . the patients ' primary surgery was performed at the gynecological department of one of the five different hospitals , and the staging procedure was done at the time of surgery . cytoreductive surgery was considered to have achieved optimal debulking when the residual disease was < 1 cm . postoperatively , all patients received at least six cycles of taxane - platin based chemotherapy . four patients had three or fewer cycles of neoadjuvant chemotherapy before staging operation and no patient had intraperitoneal chemotherapy . recurrence was defined as the earliest date when abnormal findings were detected on a follow - up ct scan . time of survival was defined as the time from diagnosis to recurrence for progression free survival ( pfs ) , and from diagnosis to death irrespective of cause for overall survival ( os ) . for censored cases survival patients were evaluated for complications , rates of optimal debulking ( residual disease<1 cm ) , pfs , os and platinum sensitivity , i.e. recurrence more than 6 months from completion of platinum - based chemotherapy . body weight and height were checked at diagnosis which means within three months before operation . body mass index ( bmi ) was calculated using the quetelet 's index expressed in kg / m and categorized into five groups : underweight ( bmi<18.5 ) , normal ( 18.5bmi<23 ) , overweight ( 23bmi<25 ) , obese i ( 25bmi<30 ) and obese ii ( 30.0bmi ) . the bmi cut - off points followed those proposed by the regional office for western pacific region of world health organization ( who ) ( wpro criteria , 2000 ) ( 9 ) . survival was analyzed using the kaplan - meier method and compared using a log - rank test . statistical analysis was performed using the chi - square test , fisher 's exact test and anova , where appropriate . this study was approved by institutional review board of korea university anam hospital ( ed10313 ) and 4 other hospitals . the subjects ' informed consent was waived by the boards due to the observation design of this study . this study was approved by institutional review board of korea university anam hospital ( ed10313 ) and 4 other hospitals . the subjects ' informed consent was waived by the boards due to the observation design of this study . five ( 2.1% ) , 85 ( 36.0% ) , 69 ( 29.2% ) , 64 ( 27.2% ) , and 13 ( 5.5% ) patients were underweight , normal weight , overweight , obese i and obese ii , respectively . age at diagnosis significantly differed across the five bmi groups ( p = 0.003 ) . the initial hb of underweight patients ( 10.41.8 g / dl ) was significantly lower compared to the other bmi groups ( p = 0.049 ) . no significant differences were seen in parity , medical history , surgery optimality , stage , ca 125 , ca 19 - 9 and follow - up time among the five bmi categories . histologic characteristics showed an even distribution across the five bmi groups , and the serous type comprised majority for each bmi group ( table 1 ) . the median pfs was 9.5 months ( 1 - 132 months ) and the 5-yr os was 47% , considering all stages for the whole series ( data not shown ) . during the median follow - up period of 21.4 months ( range , 1 - 141 months ) , a total of 56 deaths were recorded ( 23.7% ) with an even distribution across the bmi strata ( table 1 ) . table 2 shows the univariate and multivariate hazard ratios ( hrs ) and 95% confidence intervals ( cis ) for ovarian cancer mortality associated with bmi and surgical optimality . underweight patients ( bmi<18.5 ) had a significantly higher mortality compared to patients in the reference group ( 18.5bmi<23 ) ( hr , 8.622 ; 95% ci , 1.871 - 39.737 ; p=0.006 ) . the hr and 95% ci comparing women who had non - optimal surgery versus patients with optimal surgery was 2.302 ( 95% ci , 1.326 - 3.995 ; p=0.003 ) . our analysis did not find any other factors affecting the survival of stage iii and iv ovarian cancer ( data not shown ) . in the subcohort analysis , within 97 patients with serous ovarian cancers after optimal surgery , underweight patients had significantly poorer survival than other bmi groups ( p=0.031 ) and obese ii patients showed no significant difference in survival compared to normal weight , overweight and obese i patients ( p=0.097 ) ( fig . however , among the three mid - range bmi groups overweight and obese i patients had a higher rate of survival than normal weight patients ( p=0.012 ) ( fig . ovarian cancer is one of the most lethal cancers in women ; however , there is little data available on the precise nature of the relationship between obesity and ovarian cancer mortality . furthermore , there is lack of study about the effect of obesity to the ovarian cancer survival in asian population . this study examined whether bmi group following asian criteria has an association with the ovarian cancer survival . we found that an underweight bmi and surgical optimality are independent risk factors for the survival of patients with advanced ovarian cancer . however , there was no significant relationship between ovarian cancer survival and the other four bmi groups . only in the subgroup analysis with a serous histology and with optimal surgery , patients in the overweight and obese i groups had better survival than normal weight patients . the median pfs and 5-yr os of our data ( 15 months and 47% , respectively ) are pretty better than the pfs and os expected in advanced ovarian cancer patients . it seems because only patients who completed over six cycles of chemotherapy were included in this study . these results are notable because to date obesity has been shown to have only two effects on ovarian cancer survival , either a worse prognosis or no effect . ( 10 ) reported that obesity was independently associated with both shorter time to recurrence and shorter overall survival for patients with advanced ovarian cancer . our study is both of a different ethnic population and a large sample size . according to study by yang et al . however , bmi was measured one year before the diagnosis of ovarian cancer , and the bmi definition used were different from those in our study . the pathophysiology of both obesity and cancer biology is complicated , and therefore , the approach to reveal the association between them should be carefully considered . despite the technical challenge that may be present during surgery , our patients had consistent optimal cytoreduction rates across the bmi groups . this important factor in the rate of survival was emphasized in the study of matthews et al . who suggested that maximal effort should be directed towards debulking tumor mass in obese patients with eoc ( 12 ) . they reported that survival rates are similar between obese and non - obese patients when optimal debulking status is the same . underweight patients in our study showed a significantly poor survival rate than other bmi groups . although elevated bmi is associated with an increased prevalence of comorbidities , the survival rate of obese ii patients was not different from normal weight patients . these findings are similar to a study done by skrnisdttir and sorbe ( 13 ) . however , the study population in underweight and obese ii groups was very small ( five and thirteen , respectively ) so , we obtained the reliability of our results through subgroup analysis with normal , overweight and obese i patients . serous carcinoma is the most common type of ovarian cancer with a frequency of over 90% ( 14 ) . nearly all comprehensively staged patients present in advanced stage with tumor disseminated throughout the abdominal and pelvic cavities . some characteristics of serous carcinoma , including early metastasis and dissemination , can be key targets for improving the prognosis of overweight and obese i patients . it is possible that overweight status in asians with advanced ovarian cancer is a protective factor since asian obesity appears to be associated with a better prognosis than western obesity . overweight and obese i patients may be resistant to the toxicity of chemotherapy due to better initial nutritional status . one potential confounder in advanced serous ovarian cancer is that there is a discrepancy between real body mass and bmi due to the burden of ascites and multi - organ metastasis . the international obesity task force of the who proposed a system of classification based on bmi , and selected a bmi of 30.0 as the cutoff point for obesity based on mortality and morbidity outcomes ( 15 ) . in recent years , accumulating evidence has suggested that the who criteria for classifying obesity in adult caucasians may not be appropriate for asian populations . asian populations have a high level of abdominal fat at a lower bmi relative to caucasians , and show an increasing trend toward obesity . therefore , the regional office for the western pacific region of the who , the international association for the study of obesity and the international obesity task force proposed a separate classification of obesity for asian population in 2000 . this led to the proposal that overweight adults be designed as such in asia with a bmi23.0 , and that obesity be defined by a bmi25.0 ( wpro criteria ) ( 9 ) . to the best of our knowledge , this is the first study analyzing ovarian cancer survival using the asian bmi criteria . however , there are still many unanswered questions about the association between asian bmi criteria and ovarian cancer survival . some strengths and limitations of the present study should be considered when interpreting these findings . strengths include appropriate bmi criteria for asian patients , subgroup analysis excluding the effects of important variables , directly measured anthropometric variables and a study population consisting of advanced epithelial ovarian cancer . to the best of our knowledge , this is the first epidemiologic evidence showing that overweight and obese status is associated with a better prognosis . with regard to limitations , a history of medical disease was not detailed for patients enrolled in the study . nevertheless , overweight and obese i patients had better outcomes despite being older and potentially being at higher risk for cardiovascular disease . further large scale studies including other asian countries will be needed to confirm the observed associations in this study . in conclusion , underweight and surgical optimality are independent risk factors for advanced ovarian cancer survival in korean patients . bmi does not influence the survival of advanced eoc patients except in underweight patients . in the subgroup of serous histology and optimal debulking surgery , patients of the overweight and obese i groups have higher rates of survival than normal - weight patients . these results provide a useful reference for planning further studies and for predicting the prognosis of asian patients with ovarian cancer .