Clinical Abstracts
With Comments by Adriane Fugh-Berman, MD
Soy and Hot Flashes in Breast Cancer Survivors
May 2000; Volume 2; 39-40
Source: Quella SK, et al. Evaluation of soy phytoestrogens for the treatment of hot flashes in breast cancer survivors: A North Central cancer treatment group trial. J Clin Oncol 2000;18:1068-1074.
Design and Setting: Randomized, double-blind, placebo-controlled crossover trial lasting nine weeks (one week baseline, then four weeks of either treatment or placebo, after which patients were crossed over to the other arm).
Subjects: One hundred seventy-seven women with a history of breast cancer, currently without evidence of disease, who had at least 14 hot flashes per week. Subjects were stratified by age (< 40 years, n = 68; ³ 50 years, n = 132) and current tamoxifen or raloxifene use (156 women were currently using tamoxifen).
Treatment: Soy tablets (each 600 mg tablet contained 50 mg of soy isoflavones: 40-45% genistein, 40-45% daidzein, and 10-20% glycitein).
Dose/Route/Duration: One soy tablet PO tid (total intake of isoflavones was 150 mg/d).
Outcome Measures: Hot flash frequency and intensity and any side effects (diarrhea, nausea, vomiting, excess bloating/gas) assessed by diary.
Results: One hundred forty-nine patients completed the study. Percentages of patients reporting reductions in hot flash scores were similar between the two groups; the percentage of patients reporting a 50% reduction in hot flash frequency was significantly higher in the group taking placebo (36%) than in the group receiving soy (24%). Patients did not prefer soy over placebo. There were no significant differences between the two groups regarding gastrointestinal symptoms.
Funding: Public health service grants from the National Cancer Institute. Pharmavite (Mission Hills, CA) provided the phytoestrogen tablets and placebos.
Comments: This is the first study to my knowledge that has tested phytoestrogen supplementation in women taking selective estrogen receptor modulators (SERMs). Although it is stated in the study design that women were stratified by current tamoxifen or raloxifene use (yes vs. no), it is unclear whether any patients were actually taking raloxifene (in the table of baseline data, only tamoxifen is mentioned). It is not clear whether the product tested is a marketed product; also, the product was not tested to verify isoflavone content.
It would have been interesting to see whether results differed in premeno-pausal and postmenopausal women and by SERM intake. This trial differs from almost all clinical trials of phytoestrogen supplementation for hot flashes in that other trials utilized dietary supplementation instead of pills. However, isoflavones are phytoestrogens and are thought to be the active component in reducing hot flashes, so one would expect isoflavone pills to be active. This is a very interesting study showing that isoflavone supplementation does not appear to help hot flashes in breast cancer survivors (at least in women taking tamoxifen). Hot flashes can be a very uncomfortable side effect of breast cancer treatment, and physicians who see breast cancer patients are often asked whether phytoestrogen supplementation would help these symptoms. The answer, at least for pills, appears to be no.
May 2000; Volume 2; 39-40
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