Tang JY et al.– Vitamin D supplementation at a relatively low dose plus calcium did not reduce the overall incidence of nonmelanoma skin cancer (NMSC) or melanoma. However, in women with history of NMSC, calcium plus 400 IU of vitamin D3 (CaD) supplementation reduced melanoma risk, suggesting a potential role for calcium and vitamin D supplements in this high–risk group. Results from this post hoc subgroup analysis should be interpreted with caution but warrant additional investigation.Methods
- Postmenopausal women age 50 to 79 years (N=36,282) enrolled onto the Women's Health Initiative (WHI) calcium/vitamin D clinical trial were randomly assigned to receive 1,000 mg of elemental calcium plus 400 IU of vitamin D3 (CaD) daily or placebo for a mean follow–up period of 7.0 years.
- NMSC and melanoma skin cancers were ascertained by annual self–report; melanoma skin cancers underwent physician adjudication.
- Neither incident NMSC nor melanoma rates differed between treatment (hazard ratio [HR], 1.02; 95% CI, 0.95 to 1.07) and placebo groups (HR, 0.86; 95% CI, 0.64 to 1.16).
- In subgroup analyses, women with history of NMSC assigned to CaD had a reduced risk of melanoma versus those receiving placebo (HR, 0.43; 95% CI, 0.21 to 0.90; Pinteraction=.038), which was not observed in women without history of NMSC.