A combination of calcium and vitamin D may cut the chance of melanoma in half for some women at high risk of developing the life-threatening skin cancer, according to a study by researchers with the Stanford University School of Medicine.
Using existing data from a large clinical trial, the researchers focused on women with a history of non-melanoma skin cancer, saying such patients are more likely to develop melanoma. The researchers found that women who once had non-melanoma skin cancer and took the calcium-vitamin D combination developed 57% fewer melanomas than women with similar histories who were not given the supplements.
Non-melanoma skin cancers, such as basal cell or squamous cell cancers, are the most common forms of skin cancer.
In preventive medicine, we want to target people most at risk for the disease, study author and dermatologist Jean Tang, MD, PhD, said in a news release. If you previously had a non-melanoma skin cancer, calcium plus vitamin D might reduce your risk of the more deadly melanoma.
However, Tang noted, the study found that a daily dose of 1,000 mg calcium plus 400 IU of vitamin D does not provide skin cancer protection for everybody. Women without a history of non-melanoma skin cancer who took the supplements did not see any reduction of risk compared with their placebo-group counterparts, according to the research.
Tang and colleagues analyzed data from the Womens Health Initiative, a study that followed 36,000 women ages 50 to 79 for an average of seven years. Half the women took the daily dose of calcium and vitamin D as part of the experiment; the other half took a placebo pill. The WHI calcium plus vitamin D trial was designed to look at the effects of the supplement on hip fractures and colorectal cancers, but its researchers collected data on many other health issues, including other cancers.
The lack of protective effect in women without a history of non-melanoma skin cancer may be due to the amount of vitamin D given to the patients in the WHI trial, the researchers said.
The patients in the Womens Health Initiative were given vitamin D at a very low dose, based on todays knowledge only 400 IU per day, David Feldman, MD, professor emeritus of endocrinology and a co-author of the study, said in the news release. Furthermore, patients in the placebo group were allowed to take as much vitamin D as patients that were provided the calcium and vitamin D supplements, so the experimental difference between the two groups was small.
In light of that small difference, its somewhat surprising that there was an effect on melanoma risk, and I think many potential benefits of vitamin D may not have been detected, Feldman said.
“These results spur us to do more studies,” Tang said.
The study appeared June 27 on the website of the Journal of Clinical Oncology: http://jco.ascopubs.org/content/early/2011/06/27/JCO.2011.34.5967.abstract.