Cancer Epidemiology, Biomarkers & Prevention, 04/18/2014  Clinical Article

Kristal AR, et al. – The results of this study suggests that both low and high vitamin D concentrations were associated with increased risk of prostate cancer, and more strongly for high–grade disease.

Methods

• Data for this case (n=1,731)–cohort (n=3,203) analysis are from the Selenium and Vitamin E Cancer Prevention Trial.
• Cox proportional hazard models were used to test whether baseline plasma vitamin D (25–hydroxy) concentration, adjusted for season of blood collection, was associated with the risk of total and Gleason Score 2–6, 7–10 and 8–10 prostate cancer.

Results

• There were U–shaped associations of vitamin D with total cancer risk: compared to the first quintile, hazard ratios were 0.83 (95% CI 0.66–1.03, p=0.092), 0.74 (95% CI 0.59–0.92, p=0.008), 0.86 (95% CI 0.69–1.07, p=0.181) and 0.98 (95% CI 0.78–1.21, p=0.823), for the 2nd through 5th quintiles, respectively.
• For Gleason 7–10 cancer, corresponding hazard ratios were 0.63 (95% CI 0.45–0.90, p=0.010), 0.66 (95% CI 0.47–0.92, p=0.016), 0.79 (95% CI 0.56–1.10, p=0.165) and 0.88 (95% CI 0.63–1.22, p=0.436).
• Among African American men (n=250 cases), higher vitamin D was associated with reduced risk of Gleason 7–10 cancer only: in the a posteriori contrast of quintiles 1–2 vs 3–5, the hazard ratio was 0.55 (95% CI 0.31–0.97, p=0.037), with no evidence of dose–response or a U–shaped association.

1. Alan R. Kristal

Abstract

Background:In-vitro, animal and ecological studies suggest that inadequate vitamin D intake could increase prostate cancer risk, but results of biomarker-based longitudinal studies are inconsistent. Methods:Data for this case (n=1,731)-cohort (n=3,203) analysis are from the Selenium and Vitamin E Cancer Prevention Trial. Cox proportional hazard models were used to test whether baseline plasma vitamin D (25-hydroxy) concentration, adjusted for season of blood collection, was associated with the risk of total and Gleason Score 2-6, 7-10 and 8-10 prostate cancer. Results:There were U-shaped associations of vitamin D with total cancer risk: compared to the first quintile, hazard ratios were 0.83 (95% CI 0.66-1.03, p=0.092), 0.74 (95% CI 0.59-0.92, p=0.008), 0.86 (95% CI 0.69-1.07, p=0.181) and 0.98 (95% CI 0.78-1.21, p=0.823), for the 2nd through 5th quintiles, respectively. For Gleason 7-10 cancer, corresponding hazard ratios were 0.63 (95% CI 0.45-0.90, p=0.010), 0.66 (95% CI 0.47-0.92, p=0.016), 0.79 (95% CI 0.56-1.10, p=0.165) and 0.88 (95% CI 0.63-1.22, p=0.436). Among African American men (n=250 cases), higher vitamin D was associated with reduced risk of Gleason 7-10 cancer only: in the a posteriori contrast of quintiles 1-2 vs 3-5, the hazard ratio was 0.55 (95% CI 0.31-0.97, p=0.037), with no evidence of dose-response or a U-shaped association. Conclusions:Both low and high vitamin D concentrations were associated with increased risk of prostate cancer, and more strongly for high-grade disease. Impact:The optimal range of circulating vitamin D for prostate cancer prevention may be narrow. Supplementation of men with adequate levels may be harmful.