NEW YORK (Reuters Health) - Women with stage I or II breast cancer positive for BRCA mutations show longer survival with bilateral compared to unilateral mastectomy, according to a retrospective analysis.
In North America, approximately half of women with a BRCA mutation undergo mastectomy of the contralateral breast to prevent a second breast cancer, but without evidence that contralateral mastectomy reduces breast cancer related mortality, the researchers said in a February 11th online paper in the British Medical Journal.
Dr. Steven A. Narod of Women's College Research Institute, Toronto and colleagues examined data from 12 cancer genetics clinics on 390 women with a family history of stage I or II breast cancer who were carriers of BRCA1 and BRCA2 mutations.
Of these, 191 had mastectomy of the contralateral breast and the remaining 209 had unilateral mastectomy.
Only 12% of the patients were initially treated with bilateral mastectomy. Among women who initially had unilateral mastectomy, 40% later opted for mastectomy of the contralateral breast.
Most contralateral mastectomies (94%) were done in the first 10 years of follow-up.
The median follow-up was 14.3 years. Over the entire 20-year study period, the survival rate in the contralateral mastectomy group was 88%, compared to 66% in the unilateral group. In multivariable analysis, following adjustment for factors including age at diagnosis and treatment, contralateral mastectomy was associated with a 48% reduction in death from breast cancer (hazard ratio 0.52).
Given these findings, the investigators say, "it is reasonable to propose bilateral mastectomy as the initial treatment option for women with early stage breast cancer who are carriers of a BRCA1 or BRCA2 mutation."
Dr. Narod told Reuters Health by email, "Recently, there is increasing evidence that we should be offering genetic testing to women at the time of diagnosis of breast cancer, because the approach to their treatment might be different."
He added, "At Women's College Hospital we offer genetic testing for BRCA1 and BRCA2 to all women with breast cancer diagnosed before age 50 or with triple negative breast cancer. If they are positive we recommend bilateral mastectomy and oophorectomy as primary treatments."
"We find about 5% are positive and they might not otherwise be tested," he continued. "We also recommend chemotherapy to all BRCA1 positive patients with invasive breast cancer, regardless of grade or tumor size."
Commenting on the findings by email, Dr. Shoshana Rosenberg, a researcher at the Susan F. Smith Center for Women's Cancers at Dana-Farber Cancer Institute, Boston told Reuters Health, "Because women with a BRCA mutation have an increased risk of developing a new primary cancer, choosing to have a contralateral mastectomy is a reasonable option in this population."
"However," added Dr. Rosenberg, "the mortality benefit reported in this study was detected after 10 years of follow-up, indicating that women who do not initially choose to have this surgery can still consider having it later on. As the authors note, the findings of this study should be interpreted cautiously, given the small number of events (e.g., breast cancer deaths) and the observational study design."
Br Med J 2014.
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