Women who have a vitamin D deficiency when they are diagnosed with breast cancer were 94 percent more likely to have their cancer metastasize and 73 percent more likely to die within 10 years, Canadian researchers reported Thursday.
The team also found that only 24 percent of the women had what are normally considered adequate levels of vitamin D at the time of the diagnosis.
The study represents “the first time that vitamin D has been linked to breast cancer progression,” said Dr. Pamela Goodwin of Mount Sinai Hospital in Toronto, who led the study.
The results are “very provocative,” said Dr. Joanne Mortimer, a breast cancer specialist at City of Hope Comprehensive Cancer Center in Duarte, Calif., who was not involved in the study. “There is some evidence that some of the drugs we use to treat breast cancer, such as aromatase inhibitors, need vitamin D to be activated and metabolized.”
Some women who take the drugs get joint aches, she said, and when they are put on vitamin D, “they get better.”
Experts cautioned, however, that it is too soon to recommend vitamin D supplements as a general treatment for breast cancer.
“We have no idea whether correcting a vitamin D deficiency will in any way alter these outcomes,” said Dr. Julie Gralow of the University of Washington, who was also not involved in the study.
The study was released by the American Society for Clinical Oncology. It will be presented next month at a Chicago meeting of the society.
Earlier studies have suggested that vitamin D may prevent prostate and colon cancer. In laboratory dishes and animals, the chemical blocks the formation of new blood vessels feeding tumors and interferes with the growth of abnormal cells.
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