A recent review suggests that for patients who carry a BRCA1 or BRCA2 mutation with a first breast cancer, tamoxifen therapy may reduce the risk for a contralateral breast cancer (CBC).
An international group of researchers, led by Kelly-Anne Phillips, MD, reviewed observational data from three international cohorts of women carrying BRCA1 and BRCA2 gene mutations. The study was designed to determine if the standard postsurgical treatment of tamoxifen for breast cancer in the general population would also benefit women who are BRCA mutation carriers. Personal and medical histories were reviewed for 1,583 women with the BRCA1 mutation and 881 with the BRCA2 mutation; all had at least one breast cancer diagnosis.
Findings were published in the Journal of Clinical Oncology (2013;31:3091-3099, PMID: 23918944). CBCs occurred in 520 women (24% with BRCA1 and 17% with BRCA2). For BRCA1mutation carriers treated with tamoxifen, the estimated hazard ratio [HR] was 0.38 (95% confidence interval [CI], 0.27-0.55; P< 0.001); for BRCA2 mutation carriers, the HR was 0.33 (95% CI, 0.22-0.50; P< 0.001).
In 44% of the patients studied, estrogen receptor (ER) status was recorded. The first breast cancer was ER-negative for 76% of BRCA1 mutation carriers and ER-positive for 77% of BRCA2mutation carriers. Overall, 67% of ER-positive patients with breast cancer were administered tamoxifen (60% BRCA1 and 71% BRCA2) as were 17% of ER-negative patients with breast cancer (15% BRCA1 and 25% BRCA2). Study limitations included the fact that older, postmenopausal patients were more often given tamoxifen, whereas in the study population 51% of the BRCA1 patients and 35% of the BRCA2 patients were younger than age 40 at the time of their first breast cancer. In addition, women treated with tamoxifen were also more likely to have received chemotherapy and undergone oophorectomy. The authors noted that many patients elect bilateral mastectomy at the time of the first breast cancer.
Previous studies have suggested that tamoxifen reduces the risk for additional breast cancer in those who are ER-positive; this review showed a benefit in patients with either ER-positive or ER-negative status.