Freedland, Stephen J.

Abstract Background: Studies suggest that obesity is associated with lower risk of prostate cancer but more aggressive cancers. As obesity lowers PSA levels, these observations may be influenced by detection bias. We examined the association between obesity and risk of low- and high-grade prostate cancer in REDUCE, in which biopsies were largely independent of PSA. Methods: The REDUCE study tested dutasteride for prostate cancer risk reduction in men with a PSA of 2.5 to 10.0 ng/mL and a negative biopsy. Study participants included 6,729 men who underwent at least one on-study biopsy. The association between baseline body mass index (BMI <25 kg/m2 normal weight; 25–29.9 kg/m2 overweight; and ≥30 kg/m2 obese) and risk of high-grade (Gleason ≥7) or low-grade prostate cancer (Gleason <7) versus no prostate cancer was examined using multinomial logistic regression. Results: Overall, 1,739 men (27%) were normal weight, 3,384 (53%) overweight, and 1,304 (20%) were obese. Obesity was associated with lower risk of low-grade prostate cancer in both univariable (OR, 0.74; P = 0.001) and multivariable analyses (OR, 0.79; P = 0.01). In univariable analysis, obesity was not associated with high-grade prostate cancer (OR, 1.08; P = 0.50). However, in multivariable analysis, obesity was associated with increased risk of high-grade prostate cancer (OR, 1.28; P = 0.042). This analysis was not able to address how obesity may influence prostate cancer progression. Conclusions: Obesity is associated with decreased risk of low-grade and increased risk of high-grade prostate cancer. These data provide further support to the hypothesis that obesity is associated with aggressive prostate cancer. Impact: Obesity is linked with aggressive prostate cancer. Avoiding obesity may prevent the risk of developing high-grade prostate cancer. Cancer Epidemiol Biomarkers Prev; 23(12); 2936–42. ©2014 AACR.