Researchers from the Netherlands have reported that prophylactic mastectomy is very effective in preventing breast cancer in women with BRCA1/2 mutations. The details of this study were published in the March 2010 issue of the Annals of Surgery.[1]

Inherited mutations in two genes—BRCA1 and BRCA2—have been found to greatly increase the lifetime risk of developing breast and ovarian cancer. Mutations in these genes can be passed down through either the mother’s or the father’s side of the family. Women with a BRCA1 mutation have a 47-66% lifetime risk of developing breast cancer, and women with a BRCA2 mutation have a 40-57% lifetime risk of developing the disease. These statistics are compared with a 13% lifetime risk of breast cancer in the general population. Researchers from the M. D. Anderson Cancer Center have previously reported that, compared with other high-risk women, women who carry a BRCA mutation are more likely to believe that prophylactic mastectomy is the best way to reduce their risk and worry of breast cancer.

Researchers involved in the current study evaluated outcomes of 254 women with BRCA1/2 gene mutations who had prophylactic mastectomy after screening that included MRI. This study included 147 women who had bilateral mastectomy without a previous diagnosis of breast cancer and 107 women who had had breast cancer and underwent contralateral mastectomy. The latter group had been cancer-free for almost four years.

• Among the 147 asymptomatic women undergoing bilateral mastectomy, there was one occult breast cancer detected on screening.
• Invasive breast cancer was found in surgical specimens of six (4%) asymptomatic patients who had bilateral mastectomy.
• Invasive breast cancer was found in surgical specimens of five (4.3%) symptomatic patients who had contralateral mastectomy.
• No breast cancers were detected in the 147 asymptomatic women undergoing bilateral mastectomy during an observation period of 778 years.
• One breast cancer was detected among the 107 women who had contralateral mastectomy during an observation period of 580 follow-up years.

These authors concluded that prophylactic mastectomy was highly effective in preventing breast cancer in women with BRCA1/2 mutations. They suggest that women who have had bilateral mastectomy do not require continued surveillance.

Comments: These data should be helpful for women with BRCA1/2 in making a decision about prophylactic surgery.

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