ATLANTA — High-dose isoflavone soy supplements failed to control the hot flashes of breast cancer survivors in a randomized controlled trial presented in a poster at the annual meeting of the American Society of Clinical Oncology.
Although the crossover trial was halted midway for failing to show benefit, 82% of participants reduced their hot flashes during the first 4 weeks of the study. The key to their success, Dr. William C. Dooley reported, apparently was an online Internet journal that all the women filled out each day.
“Most patients, whether they started on soy or placebo, came up with triggers for hot flashes that they could avoid and decrease the frequency,” Dr. Dooley, chair of surgical breast oncology at the University of Oklahoma in Oklahoma City, said in an interview at the meeting.
“They were writing that in their journals and after the first month the hot flashes had dropped over 30% and the severity dropped dramatically just by avoidance of diet, emotion, or other triggers,” he said. “There was no difference between the soy and placebo.”
Dr. Dooley and his coinvestigators enrolled 168 breast cancer survivors for what was to be a 16-week crossover trial. All were suffering from hot flashes and had progressed at least 6 weeks beyond completion of surgery, chemotherapy, or radiation. Patients on tamoxifen or another adjuvant hormonal therapy were allowed.
The double-blind design called for all women to participate in a 4-hour-per-week exercise program and take two dietary supplements, one of which contained 130 mg of isoflavone soy. Dr. Dooley said the dose was comparable with the amount of soy in the Japanese diet and much higher than is usually studied in randomized trials.
Of the original 168 enrollees, 51 dropped out either because they failed to complete the exercise requirement or because the physicians managing their care had objections. Another 13 participants stopped using the supplements. The usual reason was gas and/or gastrointestinal distress from the soy supplement or the casein placebo. This left 104 evaluable patients in the analysis.
Dr. Dooley said the journal component was added to the trial by breast cancer survivors who “wanted to share more information than multiple choice answers when it was over.”
Patients recorded hot flash frequency, severity, and time of day as well as exercise time in Internet diaries, which they accessed by password on a server compliant with the Health Insurance Portability and Accountability Act.
This turned out to be the most interesting part of the study, according to Dr. Dooley. “There is some benefit of journaling, so they will learn to avoid hot flashes,” he said.
Although the investigators did not find soy to provide any benefit in symptom control, Dr. Dooley said they have not ruled out other advantages.
“We did not look at cholesterol, bone density, or heart disease. … Those are some things we are going to look at in future,” he said, adding that his group is assessing soy's impact on atypical hyperplasia in another ongoing trial.