Soy Phytoestrogens Do Not Alleviate Hot Flashes in Postmenopausal Women Treated

Soy Phytoestrogens Do Not Alleviate Hot Flashes in Postmenopausal Women Treated for Breast Cancer

According to a recent article in the Journal of Clinical Oncology, soy phytoestrogens appear to not alleviate hot flashes in postmenopausal women treated for breast cancer.

Chemotherapy and hormonal therapy (Nolvadex® or anti-aromatase agents) often exacerbate hot flashes and night sweats in breast cancer survivors as they tend to suppress estrogen levels. Hormonal replacement therapy (HRT), in which estrogen compounds are used to diminish these side effects in postmenopausal women, is restricted for use in breast cancer patients due to concern that such therapy may stimulate cancer growth. Soy products have been used extensively to treat such symptoms in patients with breast cancer, as the phytoestrogens in soy were thought to mimic estrogen produced by the body without properties that may cause cancer growth. However, there has been little, if any, documentation of effectiveness.

Researchers from Canada recently performed a clinical trial in to determine effectiveness of soy products in postmenopausal women with moderate hot flashes who were previously treated for early-stage breast cancer. Women in the trial received either 500 mL of a soy beverage containing 90 mg of isoflavones or a placebo (inactive substitute) which was a rice beverage. Women recorded the number and severity of hot flashes daily with a daily menopause diary for 4 weeks prior to initiation of the trial and for 12 weeks while consuming the soy or placebo beverage. There were no significant differences between the soy and placebo groups in the number of hot flashes or hot flash scores. However, both groups reported a significant reduction in hot flashes. The average isoflavone concentration in a patients blood at 6 weeks was significantly higher in women who consumed soy compared with placebo. Mild gastrointestinal side effects were experienced by both groups, but occurred with greater frequency and severity with soy.

These researchers concluded that soy beverages do not alleviate hot flashes any more than a placebo in women treated for breast cancer. Further study is required to identify safe and effective treatments for these symptoms in patients treated for breast cancer. Patients with breast cancer who experience hot flashes and night sweats may wish to speak with their physician about the risks and benefits of participating in a clinical trial evaluating novel therapeutic approaches to diminish these side effects. Two sources of information regarding ongoing clinical trials include the National Cancer Institute ( and also provides personalized clinical trial searches on behalf of patients. (Effect of Soy Phytoestrogens on Hot Flashes in Postmenopausal Women With Breast Cancer: A Randomized, Controlled Clinical Trial, Cheri L. Van Patten, Ivo A. Olivotto, G. Keith Chambers, et al, Journal of Clinical Oncology, Vol 20, Issue 6 , pp 1449-1455, 2002)

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