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CHICAGO -- Flaxseed will not ease hot flashes for women with menopausal symptoms or breast cancer survivors taking anti-estrogen drugs, according to clinical trial results.

Mean vasomotor symptom scores dropped 33% with flaxseed-spiked fiber bars, but also fell 29% with placebo fiber bars without a significant difference between groups, Sandhya Pruthi, MD, of the Mayo Clinic in Rochester, Minn., and colleagues found.

Nor did flaxseed hold any quality of life advantages for the women in the randomized trial, the group reported at the American Society of Clinical Oncology meeting.

Physicians should offer women more effective strategies for dealing with hot flashes, such as the antidepressant velflaxine (Effexor) and the pain reliever gabapentin (Gabarone, Neurontin), Pruthi suggested at an ASCO press conference.

"We do have options for women who are not wanting to take hormonal therapies like estrogen and progesterone, especially [if they have] a history of breast cancer," Pruthi told 名媛直播.

Because complementary medicine remedies like flaxseed, black cohosh, and soy are popular with women seeking relief from hot flashes, "we as clinicians do need to ask patients what are they using and what their experience is," she added.

Flaxseed contains a plant-based form of estrogen, with a weak estrogen effect, but also an estrogen antagonist effect.

As with black cohosh and soy, patient testimonials and uncontrolled trials painted an optimistic picture of flaxseed efficacy that couldn't be confirmed in phase III trials.

A pilot study with flaxseed had shown a 57% reduction in hot flash symptom scores and frequency, which now appears to have been a placebo effect.

The "disappointing" randomized trial results showed why clinical trials are necessary, noted Mark G. Kris, MD, of Memorial Sloan-Kettering Cancer Center in New York City, who chaired the press conference.

"That's what our patients deserve," he said. "They need to know they are getting an effective therapy."

The study included 188 postmenopausal women randomized to eat a fiber bar daily that contained either 410 mg of the active flaxseed lignans or 2 g protein as a placebo for six weeks.

Among them, 51% had a history of breast cancer, but no active disease, with 15% on an aromatase inhibitor and 25% on tamoxifen. None of the women were on systemic estrogens or progesterone analogues.

Women without a history of breast cancer were eligible if they had more than 28 hot flashes per week at baseline.

While flaxseed didn't reduce hot flash scores, which reflected both symptom severity and frequency, compared with baseline to a greater degree than placebo, there were side effects.

Both groups (50% to 80%) reported gastrointestinal side effects that included gas, bloating, diarrhea, and nausea, which the researchers chalked up to the fiber content of the bars. The flaxseed group showed a 7% rate of pruritus.

"Even natural products do have side effects," Kris pointed out.

Yet nonprescription remedies, such as isoflavones, black cohosh, and vitamin E, still have a place in the management of hot flashes, according to study discussant Vered Stearns, MD, of the Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins in Baltimore. Stearns served on the data safety monitoring board for the study.

These remedies "may not have much more than a placebo effect, but they don't have very much toxicity," she pointed out.

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