A new study conducted by the renowned Mayo Clinic of Rochester, MN and published in the New England Journal of Medicine is thought by many to be the most comprehensive and reliable information ever released on the effectiveness of preventive mastectomy surgery. Dr. Patrick Borgen, chief of breast surgery at the Memorial Sloan Kettering Cancer Center in New York, called the study the “first credible calculation” of how mastectomy impacts cancer risk.
Preventive mastectomy is a procedure in which healthy breast tissue is removed from women in order to prevent or reduce their risk of developing breast cancer later in life. The surgery has been performed on women who are at high risk of developing breast cancer later in life for the past 3 decades, but doctors have had little proof of the procedure’s effectiveness until now.
All 639 women included in the recent research had had their breast tissue surgically removed. The women were divided into two groups based on their perceived risk of breast cancer due to family history of the disease as well as their own medical histories.
Of the 425 women with moderate risk, only 4 developed cancer, and none died, compared to the expected diagnosis of 37.4 cases of breast cancer and 10.4 deaths among women of similar risk who did not undergo mastectomy surgery. Mastectomy surgery produced an 89.5% reduction in cancer risk among women with moderate risk for breast cancer.
Among the 214 women at high risk for breast cancer, mastectomy surgery was credited with reducing breast cancers by over 90%. Doctors predicted that, without mastectomy surgery, 30-52.9 cases of breast cancer would have been diagnosed, causing 10.5-30.6 deaths. Of the 214 women who did have mastectomies, only 3 developed cancer and 2 died from the disease.
Doctors continue to stress that preventive mastectomy is recommended only for specific women who are virtually certain to develop breast cancer later in life due to genetic or other risk factors. Also, since mastectomy surgery cannot remove all of a woman’s breast tissue and leaves between 5-10% behind, there is no guarantee that the remaining breast tissue will not someday become cancerous.
Women can protect themselves by examining their breasts for lumps each month. Certain women at high risk of developing the disease may also be prescribed the drug tamoxifen, which has been shown to reduce risk of breast cancer by 45% in clinical tests. Tamoxifen causes potentially serious side effects and is not appropriate for most women.
