Cancer - Prostate(구연) (NP-059) Does Increased Body Mass Index Lead to Elevated Prostate Cancer Risk? It Depends on Waist Circumference 가톨릭대학교 부천성모병원1, 가톨릭대학교 서울성모병원 최진봉1, 신동호, 성재우, 양종협, 조신제, 허경제, 문형우, 박용현, 배웅진, 홍성후, 이지열, 하유신 Purpose: The previous epidemiological studies about the associations between obesity and prostate cancer risk have reported inconsistent results. These discrepancies might be due to that most studies used body mass index (BMI) to analyze the relationship between obesity and prostate cancer. Therefore, in this study, we examined the association between obesity and prostate cancer based on both BMI and waist circumference (WC) using the National Health Insurance System (NHIS) database for the entire male population of Korea. Patients and Methods: Of the 5,860,389 men who underwent at least one health examination in 2009, a total of 1,917,430 men without a previous diagnosis of any other cancer were tracked through December 2015. Multiple Cox regression analysis was conducted to examine the hazard ratio (HR) and 95% confidence interval (CI) for the association between prostate cancer and obesity relative to the reference. Results: The HR for prostate cancer was lowest in people with a BMI < 18.5 and highest in those with 23.0 ≤ BMI < 25 in the multivariate-adjusted model. However, the HRs for prostate cancer showed decreasing trend with BMI over 25 (obese class 1 and obese class 2) (P for trend = 0.168). In the group with WC < 85 cm, there was also no significant change in the HRs for prostate cancer development beyond the reference BMI in the multivariable-adjusted models (P for trend = 0.158). However, in the groups with WC ≥ 85 cm (groups with 85 ≤ WC < 90, 90 ≤ WC < 95, and 95 ≤ WC), the HRs for prostate cancer increased as the BMI increased beyond the reference BMI (P for trend < .001). In addition, there was a significant interaction among categories for WC in the development of prostate cancer (P for interaction < .001). And the increasing rate of prostate cancer development risk according to BMI was greatest in the group with WC ≤ 95 cm. Conclusion: When we did not consider WC as an adjustment factor, there was no statistically significant association between BMI and prostate cancer development risk. However, in the groups with WC ≥ 85 cm, there were significant linear relations between increasing BMI and prostate cancer risk and the higher the WC category, the stronger the association was noted. Therefore WC should be estimated together when we considering obesity as a risk factor of prostate cancer development. keywords : prostate cancer, obesity, waist circumference