Evaluation of Soy Phytoestrogens for the

Treatment of Hot Flashes in 

Breast Cancer Survivors

From the Journal of Clinical Oncology, March 2000

By Susan K. Quella, Charles L. Loprinzi, Debra L. Barton, James A. Knost, Jeff A. Sloan, Beth I. LaVasseur, Debra Swan, Kenneth R. Krupp, Kathy D. Miller, Paul J. Novotny From the Mayo Clinic and Mayo Foundation, Rochester; Duluth Community Clinical Oncology Program (CCOP), Duluth, MN; Carle Cancer Center CCOP, Urbana; Illinois Oncology Research Association CCOP, Peoria, IL; Ann Arbor Regional CCOP, Ann Arbor, MI; Toledo Community Hospital Oncology Program CCOP, Toledo, OH; and Meritcare Hospital CCOP, Fargo, ND.

Address reprint requests to Charles L. Loprinzi, MD, Mayo Clinic 200 First St, SW Rochester, MN 55905; email cloprinzi@mayo.edu.

PURPOSE: Hot flashes represent a significant clinical problem for some breast cancer survivors. Safe, effective treatment is needed for this prominent clinical problem. Although it has been shown that estrogen or progesterone replacement therapy can alleviate this problem, there are continued safety concerns regarding the use of hormonal therapies in these women. Based on anecdotal information, we hypothesized that soy-derived phytoestrogens, weak estrogen-like substances in the soybean that demonstrate estrogen agonist and/or antagonist effects when they bind to estrogen receptors, could alleviate hot flashes. This current trial was designed to investigate this hypothesis.

PATIENTS AND METHODS: This double-blind clinical trial involved breast cancer survivors with substantial hot flashes. After randomization, patients underwent a 1-week baseline period with no therapy. This was followed by 4 weeks of either soy tablets or placebo. The patients then crossed over to the opposite arm in a double-blind manner for the last 4 weeks. Patients completed a daily questionnaire documenting hot flash frequency, intensity, and perceived side effects.

RESULTS: Of the 177 women who were randomized and started the study substance, 155 (88%) provided useable data over the first 5 weeks; 149 provided usable data over the entire 9 weeks. There was no suggestion that the soy product was more effective in reducing hot flashes than the placebo. At study completion, patients preferred the soy product 33% of the time, the placebo 37% of the time, and neither substance 31% of the time. No toxicity was observed.

CONCLUSION: The soy product did not alleviate hot flashes in breast cancer survivors.

Revival Soy Information from May, 2001

Several studies

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