Prophylactic Mastectomy for BRCA Gene Carriers

A new Mayo Clinic study indicates that prophylactic removal of both breasts reduces the risk of a subsequent breast cancer by 89.5 - 100 percent in women known to be carriers of mutations in the BRCA1 and BRCA2 breast cancer susceptibility genes-and thus at extremely high risk for developing the disease.

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

"Calculations predict that six to nine breast cancers should have developed in this group of carriers without prophylactic surgery," said Dr. Lynn Hartmann, the lead investigator on the study. "That translates into a risk reduction of 89.5 percent to 100 percent for bilateral prophylactic mastectomy."

An earlier Mayo Clinic study followed 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 high-risk women.

For this new study, Hartmann's team determined the BRCA1 and BRCA2 status of these original 214 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 the new study.

"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," said Hartmann. "But a question remained: Would the procedure be able to reduce risk in the highest risk group-namely BRCA1 and BRCA2 carriers?"

Hartmann said that this new study supported the conclusion that prophylactic mastectomy did have a significant preventive benefit in women with the BRCA1 and BRCA2 genetic mutations. She added that even though the number of women in the study (26) was small, a similar study by Dutch researchers on a larger group of women demonstrated the same benefit.

SOURCES:
Journal of the National Cancer Institute, November 7, 2001; 93(21):1585
The Mayo Clinic (www.mayo.edu)

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