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.