BMI is associated with larger index tumors and worse outcome after radical prostatectomy.

Background: To investigate the impact of body mass index (BMI) on tumor characteristics and biochemical recurrence (BCR) after radical prostatectomy (RP) for prostate cancer (PCa) in Japanese men.

Methods: We evaluated data from consecutive patients who had undergone RP. Data analyzed included age, preoperative serum PSA, prostatic volume, BMI (continuous or categorized (≤ 25 kg/m(2)) values), clinical and pathological findings including index tumor volume (ITV), and current status in areas such as smoker or nonsmoker and presence or absence of diabetes. We analyzed association between BMI and BCR, especially based on ITV using univariate and multivariate analysis.

Results: We analyzed data from a total of 703 patients. The median follow-up time was 38.4 months. BCR was diagnosed in 154 patients (21.9%) at a median of 9.7 months postoperatively. Multivariate linear regression analysis adjusted for preoperative variables showed a significant positive association between BMI and ITV (continuous BMI: P=0.002; categorical BMI: P<0.001, respectively), especially for higher-grade tumors (Gleason score ≥ 7). Cox proportional hazards analysis showed a significant association between continuous BMI and BCR after surgery (preoperative variables, hazard ratio (HR) 1.09, 95% confidence interval (CI) 1.02-1.16, P=0.008), independent of clinical and pathological findings. In patients with high-risk cancer, the positive association between BMI and BCR was strengthened (preoperative variables, continuous BMI, HR 1.16, 95% CI 1.07-1.26, P<0.001; categorical BMI, HR 2.11, 95% CI 1.29-3.45, P=0.003, respectively).

Conclusions: Greater BMI significantly correlates with higher rates of BCR after surgery; BMI is a preoperative variable associated with high-grade ITV. Our results suggest that the biological environment created by greater BMI may contribute to increasing tumor aggressiveness.