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Black Cohosh Herbal Remedy May be Harmful to Chemotherapy Patients (dateline September 5, 2003)

A preliminary study shows that the herbal remedy, black cohosh, may be dangerous when taken by women who are being treated with chemotherapy. Black cohosh is often taken to help relieve bothersome symptoms of menopause, particularly hot flashes. However, the study found that black cohosh may also increase the toxicity of chemotherapy, which in some cases, could be lethal. The researchers stress that women discuss with their physicians any vitamin, herbal, or other natural supplements they may be taking while undergoing breast cancer treatment.

Alternative and complementary medicines have become increasingly popular in recent years. In fact, according to the National Center for Alternative and Complementary Medicine (NCCAM), Americans spend more than $27 billion on alternative or complementary therapies each year. While anecdotal evidence reveals that many alternative or complementary medicines may be beneficial to patients, extensive research is still needed to determine whether non-traditional medicines are truly effective.

As natural remedies become more popular among cancer patients, Dr. Sara Rockwell of Yale University School of Medicine and colleagues are studying the effect of the herb, black cohosh, women undergoing treatment for breast cancer. The results of their recent study were to be presented at the annual meeting of the American Association for Cancer Research in Toronto, but the event was cancelled due to the threat of severe acute respiratory syndrome (SARS).

In the study, Dr. Rockwell and her team studied black cohosh by growing breast cancer cells in a laboratory, then exposing them to different doses of the herbal remedy. The cells were also exposed to chemotherapy drugs (specifically, Adriamycin (generic name, doxorubicin), Taxotere (generic name, docetaxel), and cisplatin) and radiation (to simulate radiation therapy).

The findings showed that black cohosh increased the level of potency of two of the three chemotherapy drugs studied: Adriamycin and Taxotere. It did not have an effect on cells exposed to cisplatin or radiation. In theory, an increased potency of cancer drugs could be beneficial. However, the levels of Adriamycin and Taxotere in breast cancer patients tend to be high, which can negatively affect other parts of the body (particularly the heart for Adriamycin). Therefore, an even greater effect of the drug from taking black cohosh could be dangerous for patients.

While alarming, the results of this study are preliminary and need to be confirmed in larger studies. It is unclear whether the effects on breast cancer cells studied in a laboratory would be the same on cells in breast cancer patients. In the study, black cohosh did not affect cells that were not exposed to chemotherapy treatment nor did the herbal remedy affect the growth of breast cancer tumors in mice.

Nevertheless, the researchers caution women undergoing cancer treatment to discuss with physicians all vitamins, herbs, and other natural supplements or treatments they may be taking. It is estimated that 80% of women may be taking these agents, according to Dr. Rockwell, and many supplements are not well regulated by the U.S. Food and Drug Administration (FDA). Researchers have noticed that many women who stop taking hormone replacement therapy (HRT) choose to take black cohosh instead.

The National Cancer Institute recommends that patients ask the following questions when considering an alternative or complementary therapy:

  • What benefits can be expected from this therapy?
  • What are the risks associated with this therapy?
  • Do the known benefits outweigh the risks?
  • What side effects can be expected?
  • Will the therapy interfere with conventional treatment?
  • Will the therapy be covered by health insurance?

Additional Resources and References