Asian Race and Risk of Prostate Cancer: Results from the REDUCE Study.

BACKGROUND: Global prostate cancer incidence rates are lower in Asian men than Caucasian men. Whether this is the result of less screening in Asian men remains to be determined. We examined whether Asian race was associated with prostate cancer diagnosis in the Reduction by Dutasteride of Cancer Events (REDUCE) study. METHODS: REDUCE was a 4-year, multicenter, randomized trial of dutasteride versus placebo for prostate cancer prevention among men who underwent prostate-specific antigen (PSA)-independent biopsies at 2 and 4 years. Eligible men were ages 50 to 75 years, had PSA between 2.5 and 10 ng/mL, and a negative prestudy prostate biopsy. We tested the association between Asian and Caucasian race and prostate cancer diagnosis using logistic regression. RESULTS: Of 8,122 men in REDUCE, 5,755 (71%) were Caucasian and 105 (1.8%) were Asian. Asians had lower body mass index (24.8 vs. 26.9 kg/m2, P < 0.001), had smaller prostate volume (35.0 vs. 43.5 cc, P < 0.001), and were less likely to have abnormal digital rectal exams (P = 0.048), but were similar in baseline age, PSA, family history of prostate cancer, and smoking status compared with Caucasian men (all P ≥ 0.164). Asian men were equally likely to receive any on-study biopsy compared with Caucasian men (P = 0.634). After adjusting for potential confounders, Asian men were less likely to be diagnosed with prostate cancer during the 4-year study (OR = 0.49; 95% confidence interval, 0.28-0.88; P = 0.016), compared with Caucasian men. CONCLUSIONS: In REDUCE, where all men underwent biopsies largely independent of PSA, Asian race was associated with lower prostate cancer diagnosis. IMPACT: These findings suggest that lower prostate cancer risk in Asian men may be due to biological, genetic, and/or lifestyle factors.