Increased body mass index as a risk factor in localized prostate cancer treated by radical prostatectomy.

Background: The association between obesity and aggressive forms of prostate cancer is controversial. We compared preoperative body mass index (BMI) and prostate-specific antigen (PSA) levels as predictive risk factors for increased prostate weight and disease aggressiveness.

Materials And Methods: This retrospective review of 464 patients with localized prostate cancer who underwent radical prostatectomy between March 1999 and October 2006 examined relationships among clinicopathological variables (BMI, preoperative serum PSA, biopsy and pathologic Gleason score [GS], and whole prostate weight) using linear and multinomial logistic regression analysis. We used multivariate regression modeling adjusting for age, year of surgery, PSA or BMI, pathologic stage, and GS.

Results: Median age of patients (51% cT1c, 69% pT2) was 61 years (41-76), mean BMI 26.50kg/m(2) (standard deviation = 4.82), mean PSA 6.8ng/ml (0.67-27.2), median prostate weight 51g (12-200), median biopsy GS 6 (3-9), and median pathologic GS 7 (4-10). GS was upgraded in 227 patients (49%) from median GS 6 to 7 (P<0.00001). Mean prostate weight was 47±13.7g for BMI<25kg/m(2) (n = 170), 47±15g for BMI 25 to 30kg/m(2) (n = 224), and 59±26g for BMI>30kg/m(2) (n = 69) (P<0.00184). Mean prostate weight was significantly higher for BMI>30 than BMI<25 (47±13g vs. 59±25g, P<0.00015). Mean PSA was significantly higher for BMI>30 than for all other patients combined (8.56 [95% CI: 6.94-10.18] vs. 8.34 [7.23-9.45]; P = 0.001). PSA was positively associated with high biopsy GS for BMI≥25 (P = 0.048) and BMI≥30 (P = 0.009) but not for BMI≤25 (P = 0.151). BMI≥30 was associated with higher pT stage (odd ratio = 1.279 [1.5-1.56]; P = 0.015). In multivariate analyses, higher BMI was associated with higher prostate weight (P = 0.036) and pT stage (P = 0.008), and higher PSA with higher biopsy GS (P = 0.002). Neither BMI nor PSA was associated with GS upgrading.

Conclusions: Higher BMI was associated with higher prostate weight and PSA, as well as with higher pT stage and pathologic GS in men undergoing radical prostatectomy, providing further evidence that obese men are more likely to have aggressive cancer. BMI thus constitutes an additional risk factor besides PSA.