Body mass index trends and role of obesity in predicting outcome after radical prostatectomy

Abstract

Objectives: One in three American men is obese (body mass index [BMI] >or=30 kg/m(2)); however, the relationship between obesity and prostate cancer is highly debated. We examined BMI trends in patients undergoing radical prostatectomy (RP) and evaluated the role of obesity in predicting biochemical failure (BCF) after RP.

Methods: From 1988 to 2006, 964 patients underwent RP and had BMI data available. The patients who had received neoadjuvant therapy or were followed up for <1 year were excluded, yielding 702 patients who were grouped by BMI and stratified by year of surgery. The postoperative Kattan nomogram was used to assess BCF risk after RP. Obese and nonobese patients' BCF rates were compared using the Kaplan-Meier method, and Cox proportional hazard models were used to assess the effect of obesity on BCF.

Results: The mean BMI (P = .02) and proportion of patients undergoing RP who are obese (P = .02) have increased, parallel to, but less than, national trends. Our obese patients had higher grade cancer and showed a trend toward having a more advanced pathologic stage. Obese patients also had a lower predicted free from BCF survival at 7 years (74.3% vs 80.1%). However, no difference was found in the obese and nonobese patients' actual observed BCF rates (P = .48), nor was obesity an independent predictor of BCF in univariate or multivariate models (P = .46).

Conclusions: The growing proportion of obesity at RP parallels, but is less than, national trends. Our data have shown that, despite the increased recurrence risk and advanced tumor parameters, obesity does not contribute to predicting BCF for a given tumor stage, grade, or prostate-specific antigen level on multivariate analysis.