Black cohosh may interfere with breast cancer drugs

Black cohosh, an herb widely used by breast cancer patients to alleviate hot flashes and other menopausal symptoms, may alter the way that cells respond to drugs commonly used to treat breast cancer, according to a Yale School of Medicine study in Breast Cancer Research and Treatment.

Recent studies have shown that many patients receiving cancer therapy are also self-medicating with complementary and alternative medicines, often without telling their physicians, said the lead researcher, Sara Rockwell, professor of Therapeutic Radiology and Pharmacology at Yale School of Medicine. "Over 30 insurers now cover at least one alternative therapy, "she said. "Out-of-pocket spending for complementary and alternative medicines was recently estimated to be $27 billion per year, similar to the out-of-pocket costs for all physician services."

She said the herb is being widely used by and recommended to breast cancer patients who are experiencing menopausal symptoms due to removal from hormone replacement therapy or to the effects of their therapy.

In this study Rockwell and her team used a widely studied mouse breast cancer cell line to see whether commercially available extracts of black cohosh altered the response of cancer cells to radiation and to four drugs commonly used in cancer therapy.

Rockwell said the black cohosh increased cell killing by two of the drugs, decreased the effectiveness of one drug, and did not alter the effects of radiation or a fourth drug. Why each agent responded differently needs to be studied further, she said, but enough is known about the herb's effects on cancer cells to caution patients about using and other over the counter agents without consulting their physicians.

"Our studies caution that black cohosh should not be considered to be a harmless herb that is inconsequential to the health of cancer patients or to the outcome of conventional cancer therapy," Rockwell said.