The association between serum vitamin D level and risk and prognosis of melanoma: a systematic review and meta-analysis

Background Vitamin D has antineoplastic effects, but the synthesis of vitamin D requires ultraviolet radiation, a known risk factor for melanoma. Objective To investigate the correlations between serum vitamin D levels and risk and prognosis of melanoma. Methods A systematic review and meta-analysis were conducted. Online databases were searched on 31 Oct 2018. Results Twenty-five studies with a total of 11166 patients with melanoma were included. There was no significant difference in serum vitamin D levels between patients with melanoma and controls [standardized mean difference (SMD), -0.185; 95% confidence interval (CI), -0.533 to 0.162]. However, the prevalence of vitamin D deficiency was significantly higher in patients with melanoma than that in controls (odds ratio, 2.115; 95% CI, 1.151-3.885). In terms of prognosis, serum vitamin D levels were significantly higher in melanoma patients with lower Breslow thickness (<= 1 vs. >1 mm: SMD, 0.243; 95% CI, 0.160-0.327). Moreover, melanoma patients with lower vitamin D levels had a significantly higher mortality rate (hazard ratio, 1.558; 95% CI, 1.258-1.931). Conclusions Vitamin D deficiency is associated with higher Breslow thickness and mortality in melanoma patients.