Circulating 25-hydroxyvitamin D concentration and risk of breast, prostate, and colorectal cancers: the Melbourne Collaborative Cohort Study.

BACKGROUND: The role of vitamin D in cancer risk remains controversial and limited data exist on associations between vitamin D and subtypes of specific cancers. We investigated associations between circulating 25-hydroxyvitamin D (25(OH)D) and risk of colorectal, breast, and prostate cancers, including subtypes.

METHODS: A case-cohort study within the Melbourne Collaborative Cohort Study included 547 colorectal, 634 breast, and 824 prostate cancers, and a sex-stratified random sample of participants (n=2,996). Concentration of 25(OH)D in baseline dried blood spots was measured using liquid chromatography-tandem mass spectrometry. Cox regression yielded adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for each cancer in relation to plasma-equivalent 25(OH)D concentration. Associations by stage and BRAF/KRAS status for colorectal cancer, estrogen receptor status for breast cancer, and aggressiveness for prostate cancer were examined in competing risks models.

RESULTS: 25(OH)D concentrations were inversely associated with risk of colorectal cancer (highest versus lowest 25(OH)D quintile: HR=0.71, 95% CI 0.51-0.98), which was limited to women (HR=0.52, 95% CI 0.33-0.82). Circulating 25(OH)D was also inversely associated with BRAF V600E positive colorectal cancer (per 25 nmol/L increment: HR=0.71, 95% CI 0.50-1.01). There were no inverse associations with breast cancer (HR=0.98, 95% CI 0.70-1.36) or prostate cancer (HR=1.11, 95% CI 0.82-1.48).

CONCLUSIONS: Circulating 25(OH)D concentration was inversely associated with colorectal cancer risk for women, but not with risk of breast cancer or prostate cancer.

IMPACT: Vitamin D might play a role in preventing colorectal cancer. Further studies are required to confirm whether vitamin D is associated with specific tumour subtypes.