BRCA mutations – What is the risk of contralateral breast cancer?

This study looked at the risk of developing contralateral breast cancer (CBC) in patients with or without BRCA mutations. The study concluded that age at the time of first cancer diagnosis is a strong risk factor for CBC in patients with BRCA.

Contralateral breast cancer (CBC) is the development of a second new breast cancer in the other breast. Women who have either the BRCA1 or BRCA2 mutations have an especially increased risk of developing CBC. For this reason, many women with BRCA mutations choose to undergo surgery to remove both breasts as a preventive measure (referred to as prophylactic bilateral mastectomy). A more precise assessment of CBC risk for patients with BRCA1/2-associated breast cancer is needed to help patients and doctors decide on the best course of action.

The current study looked at the risk of developing contralateral breast cancer (CBC) in young patients with or without the BRCA mutations. The study included 6,194 breast cancer patients, all diagnosed with cancer at less than 50 years of age. Patients were tested for the BRCA1/2 mutations, and were monitored for an average of 12.5 years for the appearance of CBC.

The risk of CBC was 3 times higher for BRCA1 mutation carriers, and 2 times higher for BRCA2 mutation carriers, compared to patients without BRCA mutations. The rate of CBC within 10 years was 21.1% for BRCA1 mutation carriers, 10.8% for BRCA2 mutation carriers, and 5.1% for non-carriers.

Young age at first cancer diagnosis was associated with increased CBC risk. Patients with BRCA mutations who had been diagnosed with their first breast cancer before the age of 41, had a 23.9% risk of developing CBC within 10 years, compared to a 12.6% risk in those diagnosed at ages 41 to 49.

The study concluded that age at the time of first breast cancer is a strong risk factor for CBC in carriers of the BRCA1 or BRCA 2 mutations.

The study could not draw firm conclusions about the effect of age in BRCA2 mutation carriers because the number of BRCA2 mutation carriers in this study was too small.