Objectives. To determine whether obesity is associated with more advanced prostate cancer (PCa) in radical prostatectomy patients and to explore the ethnic variability in body mass index (BMI) as a potential explanation for racial differences in PCa risk.

Methods. A multi-institutional retrospective analysis of the clinical and pathologic parameters was performed on data from 860 patients with PCa undergoing radical prostatectomy between 1992 and 1998. Patient height and weight was used to calculate the BMI, which categorized patients into obese (BMI 30 kg/m ² or greater), overweight (BMI 25 to 30 kg/m ² ), and normal (BMI 25 kg/m ² or less) groups. Age, serum prostate-specific antigen level, pathologic stage, and Gleason score for each group were compared. The distribution of the BMI in each of four ethnic groups was also determined.

Results. Of 860 patients, 171 (20%) were obese, 425 (49%) overweight, and 264 (31%) normal. The obese patients presented at a younger mean age (62 years, P = 0.001), had higher mean Gleason scores (6.7, P = 0.002), had a higher likelihood of Gleason score 7 or greater cancer (71%, P = 0.003), and had a lower chance of organ-confined cancer (46%, P = 0.050). The BMI was highest in blacks, followed by whites and Asians, and blacks had significantly higher grade cancers ( P = 0.045). In multiple logistic regression analysis of the BMI and race, only BMI remained an independent predictor of Gleason grade.

Conclusions. Obese patients with PCa present for radical prostatectomy at a younger age with higher grade and more pathologically advanced cancers. Blacks have higher grade cancers than other ethnic groups and, at the same time, have significantly higher BMIs. These findings suggest that obesity may in part account for the racial variability in PCa risk.