Obese men have more advanced and more aggressive prostate cancer at time of surgery than non-obese men after adjusting for screening PSA level and age: results from two independent nested case–control studies

BACKGROUND: It remains unclear whether the hemodilution effect of body mass index (BMI) on PSA levels translates to inappropriate prostate cancer (PCa) screening in obese men. To address this, we conducted two nested case–control studies within prospective cohorts of men undergoing radical prostatectomy for newly diagnosed PCa. METHODS: We identified 1817 men with BMI ⩾30 kg m(−2) (cases) and 1244 men with BMI <25 kg m(−2) (controls) who underwent surgery to treat PCa at Mayo Clinic in Rochester between 2000 and 2009. Cases and controls were frequency matched on age and PSA level. In a similar manner, we identified 206 cases and 133 controls treated at Mayo Clinic in Florida between 2006 and 2011. We employed logistic regression models to evaluate the association of pathologic features of aggressiveness with obesity status. RESULTS: After adjusting for age and PSA level, we noted that obese men in the Rochester population are more likely to present with Gleason grade 8–10 tumors (OR= 1.50; 95% CI 1.14–1.96; P=0.003) and pT3, pT4, pTxN+ stage disease (OR=1.30; 95% CI 1.05–1.62). We noted a similar association seminal vesicle involvement (OR= 1.41; 95% CI 1.03–1.92; P=0.03). Results from the smaller Florida population supported these same associations but did not achieve conventional statistical significance. CONCLUSIONS: Obese men present with more aggressive PCa tumors compared with non-obese men of similar age and PSA screening values. If confirmed, this would support the need to explore PSA-based screening in obese men to possibly account for a hemodilution effect.