There is a glaring lack of evidence that antioxidants either help or hinder, yet many women undergoing chemotherapy, radiation, and hormonal therapy do take these supplements.
A study led by Columbia University epidemiologists Heather Greenlee and Judith Jacobson and published online June 8 in the journal Cancer looked at 663 women, originally part of the large Long Island Breast Cancer Study Project. These women all received chemotherapy, radiation, or hormonal therapy, and 60 percent of them reported in interviews that they had taken antioxidants such as vitamin C, vitamin E, beta-carotene, and selenium during treatment. Most were taking high doses, defined as more than the dose of each supplement in a Centrum multivitamin.
The trouble, says Jacobson, is that nobody knows whether taking antioxidants is safe or effective for breast cancer patients. Her study did not look at outcomes between women who took supplements and those who didn’t. “We have no evidence in this study either way – that there’s any benefit or any harm,” she says, adding that breast cancer patients should tell their oncologists that they are taking the supplements.
Dr. Eric Winer, director of breast cancer oncology at Dana-Farber Cancer Institute, goes further. Laboratory experiments and studies in animals have suggested that taking antioxidants could interfere with the benefits from chemotherapy and radiation, he says. In theory, these treatments work in part by increasing the levels of “free radicals” – highly reactive forms of oxygen. Antioxidants might combat these free radicals, though no one has shown this in human studies. The effects antioxidants might have on hormonal therapy are unknown.
“The evidence is thin to zero that these agents are particularly beneficial,” adds Winer, so patients may be taking substances that do them no good and may do harm. To be on the safe side, Winer suggests, women getting treatment for breast cancer should wait to take antioxidants until the treatment is over.