Study backs oxybutynin for hot flashes in breast cancer survivors

Volume 8, Issue 2, June 2019

Summary

Researchers say the drug improves quality of life in women who can't take hormone-based therapy.

Photograph of Roberto A. Leon Ferre, M.D.

Roberto A. Leon Ferre, M.D.

Photograph of Charles L. Loprinzi, M.D.

Charles L. Loprinzi, M.D.

Research led by Mayo Clinic oncologists Roberto A. Leon Ferre, M.D., and Charles L. Loprinzi, M.D., has found that the drug oxybutynin helps reduce the frequency and intensity of hot flashes in women who are unable to take hormone replacement therapy, including breast cancer survivors.

"Hot flashes are a common symptom of menopause and can be even more severe in breast cancer survivors than they are in the general population," Dr. Leon Ferre said.

Factors that contribute to the increased severity of hot flashes in breast cancer survivors include exposure to chemotherapy, which may bring on early menopause; the use of anti-estrogen drugs, such as tamoxifen and aromatase inhibitors; and the use of medications or procedures to suppress the function of the ovaries. The use of hormone replacement therapy to treat hot flashes generally isn't recommended for breast cancer survivors.

"Hot flashes not only impact a patient's quality of life, they are associated with patients prematurely discontinuing breast cancer treatment, which may increase the risk of breast cancer recurrence and mortality," Dr. Leon Ferre said. "It is important for physicians to have effective options to treat hot flashes."

Previous research suggested that hot flashes may be relieved with oxybutynin, an anticholinergic agent that interferes with the activity of a neurotransmitter in the brain and in the peripheral nervous system. The drug is most commonly used to treat urinary incontinence.

Dr. Leon Ferre said that since oxybutynin is already available for other indications, physicians could potentially prescribe it off-label to treat hot flashes in women who are unable to take hormone replacement therapy.

However, he said his research does not address long-term toxicities of oxybutynin. Previous research has indicated that long-term use of this type of drug may be associated with cognitive decline. These possible side effects should be further researched and taken into consideration when physicians counsel patients.

The study by Drs. Leon Ferre and Loprinzi sought to determine whether oxybutynin was more effective than was a placebo in treating hot flashes and in improving quality of life. The researchers enrolled 150 women who had experienced at least 28 hot flashes a week for more than a month and who were bothered enough by the hot flashes to want medication. Sixty-two percent of the women were taking tamoxifen or an aromatase inhibitor for the duration of the study. The study had three arms, with patients in two arms receiving different dosages of oxybutynin and patients in the third arm receiving a placebo.

The study found that patients on both oxybutynin doses saw decreases in hot flashes compared with the women who took the placebo. The women in both oxybutynin arms also reported decreased interference of hot flashes in their work, social activities, leisure activities and sleep, and they saw an improvement in their overall quality of life.

"This study, in addition to previously published work in this area, establishes that oxybutynin is an effective drug for treatment of hot flashes in patients who have relative or absolute contraindications to hormone-based therapy," Dr. Leon Ferre said. "We were surprised by the rapidity of the response and the magnitude of the effect, considering the relatively low dose of the drug."

He said that oxybutynin doesn't interfere with the metabolism of tamoxifen, which is an important consideration for breast cancer survivors because some of the most-effective nonhormonal treatments for hot flashes (such as antidepressants) are thought to potentially decrease the efficacy of tamoxifen.

The study findings were presented at the 2018 San Antonio Breast Cancer Symposium.

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