A new study provides more evidence that women who are at increased risk of developing breast cancer can significantly reduce their risk by having both breasts removed, a procedure known as bilateral prophylactic mastectomy. The risk reduction in the current study was about 95 percent.

However, the researchers emphasize that the underlying absolute risk of breast cancer in most women who had both breasts removed was “modest” and the risk of dying from breast cancer was “small.”

“Prophylactic mastectomy appears to prevent breast cancer but also carries a risk of complications and may impact a woman’s psychological health,” Dr. Ann M. Geiger told AMN Health.

Women may alternatively opt to manage their risk with regular mammograms, or by taking the drug tamoxifen or having their ovaries removed, both of which have also been shown to reduce the risk of breast cancer, she said.

The results are based on a look-back at 276 women who had both breast removed as a preventive measure at a mean age of 45 and a random sample of 196 representing a population-based sample of 666,800 women who did not.

Both groups were considered to be at elevated risk for breast cancer due to the presence of at least one risk factor, most commonly a family history of breast cancer, history of atypical hyperplasia, a benign condition that could indicate an increased risk of breast cancer, or one or more breast biopsies with benign findings.

In the prophylactic mastectomy group, only one woman developed breast cancer (0.4 percent) during an average follow up of 10 years compared with an estimated 26,800 (4.0 percent) of 666,800 women who did not have the procedure and were followed for an average of 6 years, Geiger, from Kaiser Permanente’s Center for Research and Evaluation in Pasadena, California, and colleagues report.

No woman who had both breasts removed died of breast cancer versus a calculated 0.2 percent of women who did not have the procedure.

“Our results suggest a clinically meaningful reduction in breast cancer risk after bilateral prophylactic mastectomy,” the investigators write in the current issue of the journal Archives of Internal Medicine. “However, the absolute underlying risk of breast cancer and death from breast cancer was low.”

Women and their physicians “should consider the risk of breast cancer before choosing preventive options,” they conclude.

SOURCE: Archives of Internal Medicine March 14, 2005.