Vitamin D Supplementation and Melanoma Incidence and Recurrence: A Meta-analysis of Randomized Controlled Trials.

BACKGROUND: Vitamin D has been hypothesized to influence melanoma risk and progression, but observational findings are confounded by ultraviolet exposure. OBJECTIVES: To assess the effect of vitamin D supplementation on melanoma recurrence and melanoma incidence using randomized controlled trial (RCT) evidence. METHODS: A PRISMA-guided systematic review and meta-analysis identified RCTs evaluating oral vitamin D supplementation, with or without calcium, reporting melanoma incidence or recurrence. Hazard ratios (HRs) were pooled for recurrence and relative risks (RRs) for incidence using random-effects models with the Hartung-Knapp-Sidik-Jonkman (HKSJ) correction. RESULTS: Five RCTs including 56,901 participants met inclusion criteria. Vitamin D supplementation was not associated with reduced melanoma recurrence (pooled HR 1.23; 95% CI 0.29-5.18; HKSJ-adjusted) or melanoma incidence (pooled RR 0.94; 95% CI 0.71-1.24; HKSJ-adjusted). Findings were consistent across varied dosing regimens and follow-up durations. LIMITATIONS: Melanoma was a secondary endpoint in some trials, event rates were low, and dosing regimens varied. CONCLUSIONS: Current randomized evidence does not support vitamin D supplementation as a strategy to reduce melanoma incidence or recurrence.