Influence of body mass index and total testosterone level on biochemical recurrence following radical prostatectomy

Objective: A high body mass index (BMI) and a low testosterone level were recently reported to be prognostic factors for prostate-specific antigen (PSA) recurrence following radical prostatectomy (RP). The goal of this study was to clarify their relationship and influences on biochemical recurrence after RP. Methods: We analysed 126 patients whose data, including the pre-operative BMI and preoperative serum total testosterone level, were available. All patients underwent RP at our institution between March 1998 and April 2006 without any adjuvant therapy or pelvic lymph node metastasis. The Cox proportional hazards model was used for the multivariate analysis regarding PSA recurrence for the variables of age, operation period, BMI, clinical stage, PSA, Gleason's sum, pre-operative serum total testosterone level and margin status. Results: There were no internal correlations among the parameters we used, even between BMI and the total testosterone level. The total testosterone level was not different between two BMI groups (BMI <26.4 and > 26.4 kg/m(2): the cut-off is the mean + 1 SD). BMI, PSA and Gleason's sum were found to be independent predictors for PSA recurrence through the multivariate analysis. PSA recurrence-free survival rates at 2 years were 77% for BMI <26.4 kg/m2, and 31% for BMI > 26.4 kg/m(2) (P = 0.002, log-rank test, 95% CI: 1.489-7.726). Conclusions: The current study suggests that high BMI independently contributes to PSA recurrence but that the total testosterone level does not. Although the mechanism by which obesity promotes PSA recurrence in RP patients has not been established, careful observation is needed for patients with high BMI.