Obesity and biochemical outcome following radical prostatectomy for organ confined disease with negative surgical margins

Purpose: We have previously shown that men with a body mass index (BMI) greater than 35 kg/m² had higher rates of positive surgical margins and significantly higher biochemical recurrence rates following radical prostatectomy (RP). To determine whether the higher prostate specific antigen (PSA) recurrence rates were due solely to the higher positive margin rate, we examined whether obesity was an independent predictor of biochemical failure among men with negative surgical margins. Materials and Methods: We examined data from 1,250 men treated with RP between 1988 and 2003 at 5 equal access medical centers, of whom 731 had pathologically organ confined disease and negative surgical margins. Multivariate Cox proportional hazards analysis was used to determine if BMI was a significant independent predictor of biochemical recurrence. Results: Mean BMI significantly increased over time (p = 0.010). Black men were significantly more likely to be obese than white or nonwhite-nonblack men. After controlling for all preoperative characteristics, body mass index was a significant predictor of biochemical failure with moderately and severely obese men (BMI 35 kg/m² or greater) having greater than a 4-fold increased risk of PSA failure (p = 0.035). After controlling for the higher pathological Gleason grades among obese men, body mass index remained a significant predictor of biochemical failure with moderately and severely obese men (BMI 35 kg/m² or greater) having nearly a 4-fold increased risk for PSA failure (p = 0.036). Conclusions: BMI 35 kg/m² or greater was associated with higher grade tumors and worse outcome following RP in a cohort of men with favorable pathological findings. Thus, surgical technique (margin status) cannot fully explain the worse outcomes among obese men, suggesting that obesity may be associated with a biologically more aggressive form of prostate cancer.