Aromatase Inhibitors Reduce Contralateral Breast Cancer Risk in BRCA Mutation Carriers

Aromatase inhibitors can reduce risk of contralateral breast cancer in women who have a BRCA mutation, according to a new study.

“In BRCA mutation carriers who have a diagnosis of hormone-positive breast cancer, and who are not interested in undergoing risk reducing contralateral prophylactic mastectomy, adjuvant use of aromatase inhibitors may have a role in reducing their risk of contralateral breast cancer,” said lead author Maryam Nemati, MD, a fellow in the department of Breast Medical Oncology at the University of Texas MD Anderson Cancer Center, Houston, in an interview.

Dr. Nemati presented the results of the study on Friday, September 25, 2015, at the 2015 American Society of Clinical Oncology (ASCO) Breast Cancer Symposium in San Francisco (Abstract 3).

Dr. Nemati and colleagues evaluated the effect of aromatase inhibitors and tamoxifen as potential risk reducers of contralateral breast cancer in a cohort of 812 women with known BRCA status. Of these women, 153 patients had deleterious BRCA 1 or 2 mutations. The patients were followed from the diagnosis of breast cancer, until contralateral breast cancer, death, or last follow-up.

The median age of the women at diagnosis of breast cancer was 42.3 years; median follow up was 8.6 years. The vast majority of the patients had estrogen receptor-positive tumors, had been diagnosed with T1-2 disease, and had N0-N1 status. About three-quarters of them had received tamoxifen and about one-third aromatase inhibitors.

The data from the study are consistent with the reported findings of increased risk of contralateral breast cancer in BRCA mutation carriers, said Nemati. “We found that 8.8% of our cohort of BRCA 1/2 mutation carriers and noncarriers developed contralateral breast cancer,” she said. “These were the women who had not undergone prophylactic mastectomies at the time of diagnosis or during the follow-up period.

“Among our 41 BRCA mutation carriers, there were seven cases of contralateral breast cancer (17%), while in the mutation noncarriers, 36 patients (8%) experienced contralateral breast cancer.”

Multivariate analyses indicated that BRCA status and aromatase inhibitor use were significantly associated with contralateral breast cancer. BRCA 1/2 mutation carriers were more than twice as likely to develop contralateral breast cancer as noncarriers. Compared to patients who did not receive aromatase inhibitors, those who received them had smaller hazard of developing contralateral breast cancer (hazard ratio = 0.42).

All patients benefited from aromatase inhibitor use in terms of contralateral breast cancer risk reduction, she said.

“Currently, aromatase inhibitors are the treatment of choice for adjuvant therapy in postmenopausal women with hormone receptor-positive breast cancer,” said Nemati. “The role of aromatase inhibitors as chemopreventive agents and risk reducers of contralateral breast cancer in BRCA mutation carriers needs to be further validated. Our studies are suggestive that they might have a role.”