Seizure Drug Tames Tamoxifen-Induced Hot Flashes

May 21, 2002

A pilot study shows that breast cancer patients who suffer hot flashes as a side effect of tamoxifen therapy got significant relief from a common seizure medication. The University of Rochester Medical Center reports the finding today at the American Society of Clinical Oncologists annual meeting in Orlando.

The discovery should be of interest to clinicians and thousands of post-menopausal women who have already endured hot flashes naturally, and then find themselves distressed again as a result of using the popular breast cancer drug, tamoxifen.

"Our expectation is that approximately 200,000 new cases of breast cancer will be diagnosed in the U.S. in 2002. Of those patients, half will probably be treated with a drug like tamoxifen, and hot flashes are the most bothersome side effect of that treatment," says Kishan J. Pandya, M.D., professor, Hematology/Oncology at the UR Medical Center, and principal investigator of the study.

"So if you went through menopause and survived hot flashes at age 52, and then were diagnosed with breast cancer at 60 and prescribed tamoxifen, you would start all over again," Pandya says.

In 2000, the UR Medical Center was the first to observe that a seizure medication called gabapentin significantly reduced hot flashes. Thomas Guttuso Jr., M.D., reported the experiences of six patients in the August 2000 issue of the journal Neurology. Following Guttuso's observations, a group of oncologists from the James C. Wilmot Cancer Center at the UR Medical Center began investigating whether breast cancer patients could also be helped by gabapentin.

The UR's oncology team studied 19 women who were receiving tamoxifen therapy and having at least one hot flash a day. Sixteen women completed the four-week study; they took gabapentin in pill form three times a day. Of those patients, 14 showed a 70 percent reduction in the duration of their hot flashes and a 50-percent reduction in severity. Three women reported that gabapentin completely eliminated their symptoms. Gabapentin was well tolerated except for mild dizziness and drowsiness.

Gabapentin has been approved for treatment of epileptic seizures, but doctors also prescribe it for migraines and certain anxiety disorders. The pilot study in oncology was funded by a core grant through the clinical trials office of the Wilmot Cancer Center.

Oncologists are always looking for ways to manage the difficult side effects of cancer treatments, so patients will use the therapy for the prescribed time and dosage. Tamoxifen targets cancerous tissue, but in the process it stresses the body's vascular structure by acting like an anti-estrogen agent. For two-thirds of tamoxifen patients, this means experiencing the same hot flashes felt by women who shed estrogen naturally during menopause.

The next step is further scientific study. Pandya is the principal investigator for a nationwide follow-up trial, involving 200 patients testing two dose levels of gabapentin, versus a placebo pill. That trial, conducted at 18 medical centers, is expected to end later this year. It is funded by the National Cancer Institute. In addition, Pandya is testing gabapentin against a hypertension medication, clonidine, which has also been shown to reduce hot flashes in some women. It is funded by a two-year, $100,000 New York state grant.

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