Breast cancer survivors with BRCA mutations have an increased risk of developing cancer in their other breast

According to data presented at the 2011 CTRC-AACR San Antonio Breast Cancer Symposium by Alexandra J. van den Broek, M.Sc. (Netherlands Cancer Institute, Amsterdam, The Netherlands), breast cancer survivors carrying BRCA1 or BRCA2 genetic mutations have an increased risk of developing contralateral breast cancer. Moreover, based on age at diagnosis and first tumor status, certain women within this group of carriers are at an even greater risk.

“Our studies show that certain subgroups of women with BRCA mutations who have already had cancers are also at high risk of developing a second new cancer in their other breast, much more so than survivors who do not carry this mutation,” said van den Broek. In this study, researchers surveyed 5,061 women diagnosed with unilateral, invasive breast cancer at 10 hospitals in the Netherlands. Of them, 211 women (4.2%) were carriers of the BRCA1 or BRCA2 mutation. Overall, at a median of 8.4 years of follow-up, 8.6% of participants developed contralateral breast cancer. Van den Broek and colleagues found that the overall 10-year risk for developing contralateral breast cancer in noncarriers was 6.0%, while risk for carriers was as high as 17.9%. For women carrying mutations in BRCA1 this risk was 20.3% vs. 11.1% for patients with BRCA2 mutations. For carriers who were diagnosed with their first breast cancer before the age of 40, the 10-year risk for contralateral breast cancer even jumped to 26% compared to 11.6% for mutation carriers diagnosed between 40 and 50 years of age. Furthermore, mutation carriers with a first breast tumor being triple-negative, the 10-year cumulative contralateral breast cancer risk was 18.9% compared to 11.2% among mutation carriers with a non-triple-negative first tumor.

“Although these numbers can be overwhelming to BRCA mutation carriers who have already survived breast cancer, it is crucial to know who is most at risk and by how much,” van den Broek said. “Guidelines for prophylactic measures and screening in the follow-up of patients with breast cancer carrying BRCA mutations are important to provide patients with the best information and counseling,” she continued. “If these results are confirmed, it will become possible to personalize the guidelines for these specific subgroups.” The next step will be to confirm the results in larger studies and to look at other factors that define subgroups of patients with an increased or decreased risk for contralateral breast cancer.