Research results released today by the Mylan School of Pharmacy at Duquesne University indicate that the dietary supplement herbal extract black cohosh, widely used by women experiencing menopause symptoms, may not be a safe alternative therapy for women with breast cancer and may be undesirable for women that could have undetected breast tumors.
The results of the study were presented at the 94th annual meeting of the American Association for Cancer Research held in Washington, D.C.
"Although it is unfortunate to be eliminating another option for women needing therapies to relieve menopausal symptoms, our findings suggest that women who may be at high risk of having an undetected breast tumor and certainly those who do have breast cancer should proceed with great caution - or simply avoid - taking black cohosh until we learn if there are ways to circumvent these adverse effects," said Vicki Davis, Ph.D., lead researcher and assistant professor, Mylan School of Pharmacy and Graduate School of Pharmaceutical Sciences at Duquesne University.
Researchers used a transgenic mouse model in which the female mice spontaneously develop mammary tumors through the activation of an oncogene common in human breast cancer; these mammary tumors spread in time to other parts of the body, as occurs with invasive breast cancer.
To determine the effect of black cohosh on these processes, mice were fed the herbal extract in a dosage comparable to women ingesting 40 mg/day (the amount of a standardized herbal supplement normally recommended for menopausal symptoms). The sexually mature female mice were fed the black cohosh diet for 12 months.
In black cohosh-treated female mice, the incidence of new tumors was not increased, suggesting that black cohosh will not increase or decrease a women's risk of developing breast cancer. However, in the mice that developed mammary tumors, there was an increase in the number of tumors that spread to the lung (27.1% of treated mice compared to 10.9% of the mice on the control diet). The increase in the number of lung tumors per female after long-term exposure to black cohosh suggests that this herbal therapy may increase the aggressiveness of the mammary cancer.
The data presented suggest that black cohosh (at normal doses recommended for women with menopausal symptoms) may promote progression to metastatic disease in women with early stage breast cancer.