This population-based cased-control study in Philadelphia consisted of 949 breast cancer cases and 1,524 controls. Herbal supplements including black cohosh, ginseng and red clover were the most prevalent preparations. After adjusting for potential confounding factors, black cohosh use was associated with a 61 percent reduction in the risk of breast cancer with an odds ratio of 0.39, 95% CI: 0.22-0.70. The breast protective effect was similar for a specific black cohosh preparation, Remifemin, odds ratio 0.47, 95%, CI: 0.27-0.82.
Rebbeck T, Troxel A, Norman S, et al. A retrospective case-control study of the use of hormone-related supplements and association with breast cancer. Int. J. Cancer 2007; 120:1523-1528.
Comments: Women included in the study were those with a first primary, invasive, breast cancer of stage I, II, III, of any grade and any tissue type (ductal, lobular, mucinous, papillary, mixed.) Women with ductal carcinoma in situ or lobular carcinoma in situ were excluded.
This is not the first study that has indicated anti-proliferative, anti-estrogenic effects of black cohosh on breast cancer cells, especially estrogen receptor (ER) positive breast cancer cells. In the current study, black cohosh and/or Remifemin persisted irrespective of ER status. On the other hand, the effect of black cohosh and/or Remifemin varied by progesterone receptor (PR) status. The effect was significant in PR positive tumors but not in PR negative tumors. This suggests that PR status may be related to the protective effects of black cohosh on the breast.
While the researchers in this study, incorrectly describe black cohosh as containing phytoestrogens, this study is yet one more positive finding on the safety of black cohosh for breast cancer survivors with menopausal symptoms.
