ABSTRACT
BACKGROUND: Epidemiologic studies have reported inconsistent associations of vitamin D and prostate cancer risk; however, few have adequately controlled for detection bias related to prostate-specific antigen (PSA) screening, and the results of many studies may be affected by occult prostate cancers among controls. METHODS: Data for this nested case-control analysis (n = 1,695 cases/1,682 controls) are from the Prostate Cancer Prevention Trial. Baseline serum was analyzed for 25-hydroxyvitamin D [25(OH)D]. The presence or absence of cancer was subsequently determined by prostate biopsy. Polytomous logistic regression models were used to estimate associations of 25(OH)D with risk of total, Gleason 2-6, Gleason 7, and Gleason 8-10 prostate cancer. Results are presented for placebo and finasteride arms separately and combined. RESULTS: There were no associations of serum 25(OH)D with total prostate cancer risk. For Gleason 2-6 cancers, results were inconsistent across treatment arms with a suggestion of increased risk in the placebo arm only; however, there was no dose-response relationship. For Gleason 8-10 prostate cancers, 25(OH)D concentrations were associated with a linear decrease in risk among combined treatment arms [quartile 4 vs. 1: OR, 0.55; 95% confidence interval (CI), 0.32-0.94; P(trend) = 0.04]. These findings were somewhat stronger among men ≥65 versus 55-64 years at baseline (quartile 4 vs. 1: OR, 0.40; 95% CI, 0.18-0.88 vs. OR, 0.73; 95% CI, 0.35-1.52, respectively; P(interaction) = 0.52). CONCLUSIONS: Higher serum 25(OH)D may modestly increase risk of Gleason 2-6 disease and more substantially reduce risk of Gleason 8-10 prostate cancer. IMPACT: Vitamin D may have different effects for different stages of prostate cancers.
