Evaluation of soy phytoestrogens for the treatment of hot flashes in breast cancer survivors: A North Central Cancer Treatment Group trial

Purpose: Hot flashes represent a significant clinical problem for some brea st 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, wea k estrogen-like substances in the soybean that demonstrate estrogen agonist and/or antagonist effects when they bind to estrogen receptors, could alle viate hot flashes. This current trial was designed to investigate this hypo thesis, Patients and Methods: This double-blind clinical trial involved breast canc er survivors with substantial hot flashes, After randomization, patients un derwent a I-week baseline period with no therapy, This was followed by 4 we eks of either say tablets or placebo. The patients then crossed over to the opposite arm in a double-blind manner for the last 4 weeks. patients compl eted ct daily questionnaire documenting hot flash frequency, intensity, and perceived side effects. Results: Of the 177 women who were randomized and started the study substan ce, 155 (88%) provided useable data over the first 5 weeks; 149 provided us able data over the entire 9 weeks, There was no suggestion that the say pro duct was more effective in reducing hot flashes than the placebo, At study completion, patients preferred the say product 33% of the time, the placebo 37% of the time, and neither substance 31% of the time. No toxicity was ob served. Conclusion: The say product did not alleviate hot flashes in breast cancer survivors. J Clin Oncol 18:1068-1074, (C) 2000 by American Society of Clini cal Oncology.