SAN ANTONIO – BRCA mutation carriers can be separated into subgroups at low and sharply increased risks of developing contralateral breast cancer following a first breast cancer, a Dutch study suggests.
The key predictive variables identified in the BOSOM (Breast Cancer Outcome Study of Mutation) carriers were the patient’s age at diagnosis of the first breast cancer and whether or not the tumor was triple negative – that is, estrogen receptor–, progesterone receptor– and HER2 receptor–negative, Alexandra J. van den Broek reported at the annual meeting.
Dr. Alexandra van den Broek
The BOSOM study analysis included 5,065 consecutive women diagnosed with breast cancer before age 50 at 10 Dutch hospitals during 1970-2003, all of whom were tested for BRCA mutations. The prevalence of BRCA1 mutations was 3%, while another 1% had a BRCA2 mutation.
The cumulative 10-year risk of developing contralateral breast cancer (CBC) was 6% in women with no BRCA mutations, 11% with a BRCA2 mutation, and 20% in those with a BRCA1 mutation.
The subgroup of BRCA mutation carriers at greatest risk for CBC consisted of those whose first breast cancer was diagnosed before age 41. They had a 26% rate of CBC during the next 10 years. That was nearly eightfold greater than the nearly 4% figure in the low-risk subgroup, which comprised BRCA mutation carriers with a non–triple-negative cancer diagnosed at age 41-50 years, said Ms. van den Broek, a doctoral candidate in epidemiology at the Netherlands Cancer Institute, Amsterdam.
The other high-risk subgroup of BRCA mutation carriers consisted of women with a triple-negative first breast cancer diagnosed at age 41-50 years, she added. Their 10-year cumulative risk was 15%.
The number of BRCA mutation carriers in this consecutive series of breast cancer patients was fairly small, so the BOSOM results require confirmation in other data sets. If that’s forthcoming, a change in practice guidelines for prophylaxis and screening in following breast cancer patients with a BRCA mutation will be warranted, Ms. van den Broek asserted.
The study was sponsored by the Dutch Cancer Society. Ms. van den Broek declared having no financial conflicts.