Impact of obesity on the utility of preoperative prostate-specific antigen velocity to predict for relapse after prostatectomy: a report from the SEARCH database.

OBJECTIVES: To test the validity of preoperative prostate-specific antigen velocity (PSAV) (the rate of PSA rise before diagnosis) as a predictor for relapse after radical prostatectomy, in the context of patient obesity as measured by body mass index (BMI).
METHODS: The rates of biochemical relapse were examined among 215 patients who underwent radical prostatectomy between 1992 and 2005. Kaplan-Meier relapse rates as a function of preoperative PSAV 2 ng/mL/yr or less versus greater than 2 ng/mL/yr were compared in two groups: nonobese patients (normal to overweight, BMI less than 30 kg/m2) and obese patients (mild to severely obese, BMI 30 kg/m2 or greater).
RESULTS: A preoperative PSAV greater than 2 ng/mL/yr was associated with higher relapse rates after radical prostatectomy compared with a PSAV of 2 ng/mL/yr or less, with 5-year relapse-free survival rates of 60% versus 70%, respectively (P = 0.03). Prostate-specific antigen velocity was independently significant on multivariate analysis, along with biopsy Gleason score, percent positive cores, and BMI. In this study 24% of patients were obese. Prostate-specific antigen velocity greater than 2 ng/mL/yr was associated with higher relapse rates in nonobese patients (P = 0.01) but not in obese patients (P = 0.9). The two BMI groups did not differ with respect to any factors. Obese patients with slowly rising PSA (PSAV 2 ng/mL/yr or less) fared just as poorly as nonobese patients with rapidly rising PSA (PSAV greater than 2 ng/mL/yr). Obesity was independently associated with higher relapse rates.
CONCLUSIONS: Preoperative PSAV greater than 2 ng/mL/yr was associated with a higher risk of relapse after radical prostatectomy, but its clinical usefulness might be limited to nonobese patients. Obesity conferred higher relapse rates, regardless of other prognostic factors including preoperative PSAV.