Background: Findings from epidemiologic studies examining associations of serum retinol and carotenoids with prostate cancer risk have been inconsistent. This case-control study nested in the Prostate Cancer Prevention Trial evaluated associations of serum retinol and carotenoids with total, low-, and high-grade prostate cancer risk in a highly screened study population. Methods: We used logistic regression adjusting for age, family history of prostate cancer, race, body mass index, and serum cholesterol to estimate ORs and 95% confidence intervals (CI) of prostate cancer by quartiles of serum retinol and carotenoids, separately in the placebo (975 cases/1,009 frequency-matched controls) and finasteride (708 cases/743 frequency-matched controls) arms of the trial. Results: Serum retinol concentrations were associated with increased risk of total prostate cancer [OR (95% CI) comparing the highest quartile of serum retinol with the lowest: 1.30 (1.00-1.68)] and high-grade prostate cancer [OR (95% CI), 1.74 (1.14-2.68)] in the placebo arm of the trial only. Also in the placebo arm, there was a moderate positive association of a-carotene with risk of total prostate cancer [OR (95%CI), 1.32 (1.01-1.73)]. None of the other carotenoids was associated with prostate cancer risk in the placebo arm. No associations were observed for retinol and carotenoids in the finasteride arm. Conclusion: In the placebo arm of this prospective study, high serum retinol and a-carotene concentrations were associated with increased risk of total and high-grade prostate cancers. Impact: Men with higher levels of serum retinol and a-carotene may be at increased risk for prostate cancer.
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