Calcium, vitamin D combination cuts risk of melanoma in some patients
Palo Alto, Calif. — Supplementation with a combination of calcium and vitamin D may cut the chance of melanoma in half for a group of high-risk women, researchers at Stanford University say.
A post hoc analysis of a very large, randomized, controlled trial of calcium and vitamin D supplementation found no statistically significant association with incidence of melanoma. However, the study did reveal trends toward protection in higher-risk patient populations.
Women with a history of nonmelanoma skin cancer who took the combination developed 57 percent fewer melanomas than women with similar histories who did not take the supplements, investigators found.
The analysis involved 36,282 participants in the Women's Health Initiative who received either 1,000 mg of calcium plus 400 IU of vitamin D3 (CaD) or placebo daily for a mean follow-up period of seven years. Participants were postmenopausal women ages 50 to 79. The principle purpose was to evaluate the impact on bone health and risk of fracture.
The study's lead author says the findings give evidence of a role for calcium and vitamin D in the prevention of skin cancer.
"This is probably the strongest piece of evidence for a role of calcium and vitamin D in skin cancer prevention, because the Women's Health Initiative was a randomized, controlled trial, unlike some of the other studies which were case-controlled or cohort studies," says Jean Y. Tang, M.D., Ph.D., a dermatology researcher at Stanford University and lead author of the paper in the Journal of Clinical Oncology.
No overall protective effect among all women was found, although the cumulative hazard ratio of the two groups began to diverge at year five.
The analysis hypothesized that CaD supplementation might have more of an effect in subjects who were likely to already be low in vitamin D: women who are older (70s compared to 50s), have higher BMI and who lived in areas of lower sun exposure.
In the high-risk group of women with a prior history of basal cell or squamous cell cancers — "They have already had enough UV damage to sustain some types of cancer," Dr. Tang says — there was a 57 percent reduction in the risk of melanoma, which was statistically significant.