News Release

Mayo Clinic study finds prophylactic mastectomy reduces breast cancer risk in highest-risk group of women — carriers of BRCA1 and BRCA2 mutations

Peer-Reviewed Publication

Mayo Clinic

ROCHESTER, MINN. -- A Mayo Clinic study shows that prophylactic removal of both breasts reduces the risk of a subsequent breast cancer by 89.5 percent to 100 percent in women known to be carriers of mutations in the BRCA1 and BRCA2 susceptibility genes.

The study, published in the Nov. 7, 2001, issue of the Journal of the National Cancer Institute followed 26 high-risk women, identified with altered BRCA1 and BRCA2 breast cancer susceptibility genes. All of these women had previously undergone surgery to have their breasts removed. During the period of follow-up thus far — averaging 13.4 years — none of these women have developed breast cancer.

"Calculations predict that six to nine breast cancers should have developed in this group of carriers without prophylactic surgery," says Lynn Hartmann, M.D., a Mayo Clinic oncologist and lead researcher on this study. "That translates into a risk reduction of 89.5 percent to 100 percent for bilateral prophylactic mastectomy."

This study is the latest in ongoing research at Mayo Clinic about prophylactic mastectomy and subsequent breast cancer risk. The original research group included 214 women with a strong family history of breast cancer who had previously had prophylactic mastectomy. Women in this surgical group were compared with their sisters who had not had prophylactic mastectomy. That study showed that prophylactic mastectomy reduced the risk of subsequent breast cancer by approximately 90 percent.

For this most recent study, investigators worked to determine the underlying BRCA1 and BRCA2 status of these high-risk women. Blood samples were obtained from 176 of the 214 women. Twenty-six of these women were identified to have altered BRCA1 and BRCA2 genes and they formed the study group for this JNCI report.

"Our previous study had shown that prophylactic mastectomy reduced subsequent breast cancer risk substantially in women who had the procedure because of a strong family history," Dr. Hartmann says. "But a question remained: Would the procedure be able to reduce risk in the highest risk group — namely BRCA1 and BRCA2 carriers? Our current data support that it can, although ours is a relatively small group of carriers. These data complement the Dutch study published this past summer, which showed similar risk reduction in a larger number of carriers who had had prophylactic mastectomy. Their study had a relatively short period of follow-up, however."

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Contact: Mary Lawson
507-284-5005 (days)
507-284-2511 (evenings)
e-mail: newsbureau@mayo.edu


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