Calcium and Vitamin D May Reduce Melanoma Risk in High-Risk Women

From Medscape Medical News
Fran Lowry

February 7, 2011 (New Orleans, Louisiana) — A new analysis of the Women's Health Initiative (WHI) study suggests that calcium and vitamin D supplementation reduce the risk for melanoma in women at high risk for the disease because of a history of nonmelanoma skin cancer.

The finding was presented in a late-breaking abstract session here at the American Academy of Dermatology 69th Annual Meeting by Teresa Fu, a medical student at Stanford University School of Medicine in Palo Alto, California.

"There is a lot of interest in vitamin D and whether it can affect your risk for cancer," Ms. Fu told Medscape Medical News. "Researchers here at Stanford and others have shown that mice lacking vitamin D receptors have more skin cancer, and in vitro studies have shown that adding vitamin D to skin cancer cells sometimes reduces their growth. We wanted to see whether people taking vitamin D and calcium supplements might have a lower risk of skin cancer."

Ms. Fu and her team did a retrospective analysis of one part of the WHI trial that had randomized 36,282 postmenopausal women to vitamin D and calcium supplements or placebo and then followed them for 7 years to see if the supplements would ward off hip fracture and colon cancer.

The women, who ranged in age from 50 to 79 years, received 1000 mg of calcium and 400 IU of vitamin D3 or placebo daily and self-reported their health outcomes every year.

The Stanford researchers searched the data for the incidence of nonmelanoma and melanoma skin cancers in the 2 groups of women. Nonmelanoma skin cancers were ascertained by annual self report, and melanoma cases were adjudicated by physicians.

Overall, there were no differences in the rates of nonmelanoma skin cancers, which included basal cell and squamous cell carcinoma, and melanoma in the 2 groups. The hazard ratio (HR) was 1.02 (P = .59) for the treatment group and 0.86 (P = .32) for the placebo group.

However, when the researchers looked at outcomes in different subgroups, an important difference emerged. In women with a history of nonmelanoma skin cancer, calcium and vitamin D supplementation reduced the risk for melanoma by almost 55% (HR = 0.43; P = .038).

In women without a history of nonmelanoma skin cancer, there was no reduction in risk with calcium and vitamin D supplementation (HR = 1.02), Ms. Fu reported.

A separate analysis of the WHI data also revealed that women who had lower serum 25-hydroxyvitamin D levels at study entry had a higher risk for melanoma.

"These findings suggest a possible role for calcium, vitamin D, or both in reducing melanoma risk in women who are at high risk for melanoma because of history of nonmelanoma skin cancer," she said.

Coauthor Jean Y. Tang, MD, also from Stanford School of Medicine, pointed out that this is the first time that the WHI trial of calcium and vitamin D supplementation has shown a difference in the efficacy of anything.

"It didn't show a reduction in breast cancer or colon cancer, and it only showed a mild reduction in hip fractures with supplementation, so it is amazing that we are seeing some signal that it may actually be reducing melanoma, although just in women with a history of skin cancer," she said. "As a dermatologist, this is exciting for me because these are the patients I worry about. I also want to be able to tailor my prevention methods."

Ms. Fu added that "so many people have had basal cell and squamous cell cancer and they are known to have higher risks of melanoma, so it may be that a vitamin D and calcium supplement may be useful for that subgroup to prevent much deadlier melanoma."

"The beauty of this study is that it really looked at the Women's Health Initiative population," said Richard L. Gallo, MD, PhD, professor and chair of the Department of Dermatology at the University of California at San Diego. "There was a large population base and there were some trends to suggest a potential for benefit."

But, he continued, "there are a number of potential confounders in the study. It supports the need for other studies to be done specifically to answer this question, so it is supportive but not conclusive."

Ms. Fu and Dr. Tang have disclosed no relevant financial relationships. Dr. Gallo reports financial relationships with Allergan, Ceregenex, Galderma, Inimex, Intendis, Johnson and Johnson, Novartis, and Skin Epibiotics.

American Academy of Dermatology (AAD) 69th Annual Meeting. Presented February 5, 2011.