Study: Tamoxifen and Estrogen Have Similar Positive Effects on the Brain

Tamoxifen and estrogen have similar positive effects on the brain, according to researchers at Harbor-UCLA Research and Education Institute in Torrance, California.

Researchers said this finding that may lessen concerns about the safety of the drug when used to reduce the risk of breast cancer in elderly women.

Tamoxifen (Nolvadex) interferes with the activity of estrogen and is used to treat both advanced and early stage breast cancer. It also is used as an additional therapy following primary treatment for early stage breast cancer.

Prior studies have suggested that estrogen may improve brain function, so there has been concern that tamoxifen may block estrogen's beneficial effects on the brain and possibly cause some cognitive decline.

"Based on the increase in hot flashes that are associated with tamoxifen, it has been suggested that the drug blocks the potentially favorable effects of estrogen on the brain. We've found just the opposite," said Dr. Rowan Chlebowski, of Brookhaven National Laboratory in New York and co-author of the study.

"We were surprised to find similarities between the two groups in that women who have been treated with tamoxifen had lower levels of myo-inositol, a chemical that increases in response to brain injury. Women who took estrogen also had lower levels of the chemical," he said.

Researchers used Proton Magnetic Resonance Spectroscopy (MRS), a non-radioactive brain imaging technique, to measure levels of myo-inositol to predict the effects of tamoxifen. Levels of myo-inositol were compared in 16 breast cancer patients who had been treated with tamoxifen for at least two years, 27 healthy women who had been treated with estrogen replacement therapy for at least two years, and 33 healthy women who had not received either treatment. The women were all between the ages of 65 and 80.

Researchers found that women who were treated with tamoxifen had lower levels of myo-inositol in the brain than the untreated women. Women who were given estrogen also had lower levels of the brain chemical.

The lower levels of myo-inositol in women treated with tamoxifen or estrogen show that both tamoxifen and estrogen may be have some protective effect on the brain, the researchers reported in the Journal of the National Cancer Institute.

However, further studies are needed to look at the long-term effects of tamoxifen and estrogen therapy on cognitive function.

Other Sources: Journal of the National Cancer Institute, Harbor-UCLA Research and Education Institute