MP14-13 WEIGHING IN ON ACTIVE SURVEILLANCE: IMPACT OF OBESITY ON PATIENT COUNSELING

Abstract

INTRODUCTION AND OBJECTIVES: The association between body mass index (BMI) and prostate cancer (PC) risk is mixed. Some have speculated that this relates to the fact that BMI is only a moderate measure of adiposity and that perhaps better measures (total percent body fat) or that central adiposity (waist circumference) may better correlate with PC risk. We tested multiple measures of adiposity and PC risk using prospectively collected and measured data from men undergoing prostate biopsies in a Veterans Affairs hospital. We hypothesized that on the aggregate level, BMI, total percent body fat and waist circumference would be highly correlated and that all would be associated with aggressive PC, but not overall incidence. METHODS: We used data from a case-control study among veterans between 2007 and 2012 undergoing prostate biopsy at the Durham Veterans Affairs. The sample consisted of 323 (46%) with biopsy-positive PC (cases) and 375 (54%) biopsy negative (controls). We abstracted Gleason score and race from the records. Weight, height, and waist circumference were measured by trained personnel. Body fat was measured using bio-impedance. We used logistic regression to obtain odds ratios (ORs) and 95% confidence intervals (CIs) to test the association between adiposity measures and PC risk. Multinomial logistic regression was used to examined high-grade PC (Gleason 7e10) vs. low-grade (2e6) vs. no-PC. RESULTS: BMI was strongly related to percent body fat (Spearman, r1⁄40.81) and waist circumference (r1⁄40.87). Men with higher BMI had significantly higher TRUSprostate volumes, percent body fat, and waist circumference. In both adjusted and unadjusted logistic regression analyses, all three adiposity measures were unrelated to total PC risk (all p>1⁄40.14). However, when stratified by Gleason score, all adiposity measures were associated with a significantly increased risk of high-grade disease (all p 1⁄40.35). CONCLUSIONS: BMI, body fat and waist circumference are all highly correlated with each other and all were significantly associated with aggressive PC, but not overall PC risk. Despite individual differences in these measures, this study supports the continued use of BMI in epidemiological studies of obesity and PC.