BRCA mutation carriers who have had breast cancer are at increased risk of developing contralateral breast cancer, according to a study presented at the 2011 CTRC-AACR San Antonio Breast Cancer Symposium. In fact, women with a BRCA1 or BRCA2 mutation had a greater than 10% risk of developing contralateral breast cancer, and the risk was strongly associated with younger age at diagnosis and a diagnosis of triple-negative (estrogen receptor–negative, progesterone receptor–negative, and HER2-negative) breast cancer.
“As far as we know, this is the first study to show that subgroups of BRCA1 or BRCA2 carriers have an increased or decreased risk of contralateral breast cancer,” said Alexandra J. van den Broek, MSc, a doctoral candidate at the Netherlands Cancer Institute in Amsterdam.
The study included 5061 women who were diagnosed with unilateral, invasive breast cancer at 10 different institutions in the Netherlands. Of these, 211 (4.2%) were carriers of the BRCA1 or BRCA2 mutation. At a median follow-up of 8.4 years, 8.6% of the women developed contralateral breast cancer.
The overall 10-year risk for developing contralateral breast cancer was 6% in noncarriers versus 17.9% in carriers. Among carriers who were diagnosed with their first breast cancer before age 40, the 10-year risk of developing contralateral breast cancer rose to 26%; carriers between the ages of 40 and 50 years at first diagnosis had a 10-year risk of 11.6%. Mutation carriers diagnosed at first with triple-negative breast cancer had a 10-year risk of developing contralateral breast cancer that reached 18.9%, compared with 11.2% among carriers whose first cancer was not triple-negative.
When asked whether knowing their risk of developing contralateral breast cancer might be overwhelming to carriers, who are already anxious over their mutational status, van den Broek said it is crucial to know who is at risk and by how much. In her view, these findings point to the importance of revisiting current guidelines for mutation carriers and incorporating risk factors such as younger age at first diagnosis of breast cancer and a diagnosis of triple-negative breast cancer when considering prophylactic measures and screening.
“If these findings are confirmed, it will be possible to personalize the guidelines for these specific subgroups,” she stated.