Obesity as a predictor of biochemical recurrence and survival after radiation therapy for prostate cancer.

OBJECTIVE Obesity has been demonstrated to predict biochemical progression in men undergoing radical prostatectomy for prostate adenocarcinoma, and is associated with a higher risk of biochemical and clinical relapse after radiation therapy (RT). We evaluated if obesity, determined by body mass index (BMI), is associated with adverse disease characteristics, pre-treatment serum testosterone, biochemical disease free survival (bDFS), disease-specific survival (DSS), or overall survival (OS) in patients undergoing radical external beam radiation therapy for prostate cancer. PATIENTS AND METHODS A cohort of 706 patients with localized prostate adenocarcinoma treated with RT between 1993 and 2001 were categorized as obese (BMI > or = 30 kg/m(2)), overweight (BMI 25-29.9 kg/m(2)) or normal (BMI < 25 kg/m(2)). The association between BMI, disease characteristics, and progression were evaluated by Chi-square and ANOVA tests, Kaplan-Meier survival analysis, and Cox regression analysis. RESULTS 195 patients (27.6%) were normal weight, 358 (50.7%) were overweight and 153 (21.7%) were obese. Obese men had lower serum testosterone levels than overweight and normal-weight men (means 12.8, 14.1, and 15.7 nmol/L, respectively; p < 0.001). The BMI groups did not differ in Gleason score, pretreatment PSA, or stage. On multivariate analysis, BMI group was predictive of reduced bDFS (p = 0.02) and DSS (p = 0.008), with a trend toward reduced OS (p = 0.062). CONCLUSION Obesity was associated with lower serum testosterone levels but not with adverse pretreatment pathological features. Obese men have a higher risk of biochemical recurrence and prostate-cancer specific death after RT.