CHICAGO – Eating bars rich in flaxseed failed to reduce hot flashes for postmenopausal women in a randomized, placebo-controlled, phase III trial conducted by the North Central Cancer Treatment Group.
Mean hot flash scores fell comparably in both arms of the study, which enrolled breast cancer patients and women who never had the disease. Instead of relief from this troubling symptom, many participants reported GI distress.
"Our findings do not support the use of 410 mg of flaxseed lignans for the reduction of hot flashes. The gastrointestinal side effects seen in both groups were more likely due to the fiber content in the flaxseed and the placebo bars," said Dr. Sandhya Pruthi of the Mayo Clinic in Rochester, Minn. She presented the results at the annual meeting of the American Society of Clinical Oncology.
"Because hot flashes can negatively impact quality of life for many women, there is increasing interest in the use of complementary therapies such as flaxseed," Dr. Pruthi said, laying out the rationale for the trial.
Flaxseed is an annual plant, rich in lignans, which are a major class of phytoestrogens, she said. It is thought to have a weak estrogenlike effect, as well as estrogen antagonist effect.
In 2005, a pilot study of flaxseed was conducted in 30 women. They were given 400 mg of ground flaxseed, and investigators reported a 57% reduction in hot flash scores and a 50% reduction in hot flash frequency. This – along with a patient who claimed that flaxseed was successful in treating her hot flashes – led to the current trial, said Dr. Pruthi.
To be eligible, women with or without a history of breast cancer had to have more than 28 hot flashes per week. In all, 188 women were enrolled and 178 were randomized (88 to flaxseed bars containing 410 mg of lignans and fiber, and 90 to placebo bars containing protein and fiber, but no flaxseed, soy, or lignans). For 6 weeks, the participants were to eat one bar per day. The primary end point was a change from baseline in hot flash scores at week 6.
Of the entire group, 91 had a history of breast cancer but were without active disease. This group included women who were being treated with an aromatase inhibitor or tamoxifen.
Mean hot flash scores decreased by 4.9 units (about 33%) in the flaxseed arm, and 3.5 (about 29%) in the placebo arm (P = .29). "There was no significant difference in the reduction of hot flash scores between the two arms," said Dr. Pruthi.
No statistically significant toxicity was experienced by women in either arm, but both groups reported abdominal distention, gas, diarrhea, and nausea.
Although the results were disappointing, the trial does not leave women without remedies for hot flashes. Dr. Pruthi noted that venlafaxine and gabapentin were effective, and had been studied in randomized, placebo-controlled trials. "So we do have options for women who are not wanting to take hormonal therapies like estrogen or progesterone, especially with a history of breast cancer," she said.
"However, there are side effects with those drugs. Patients need to balance between treating their symptoms and managing their side effects, which is why we need to do more studies in other complementary therapies that we think might have [fewer side effects] and still give us the benefit of treating hot flashes," she said.
Dr. Pruthi reported having nothing to disclose. This study was funded by the National Cancer Institute.