Contralateral risk-reducing mastectomy in BRCA1 and BRCA2 mutation carriers and other high-risk women in the Kathleen Cuningham Foundation Consortium for Research into Familial Breast Cancer (kConFab)

Abstract

The purpose of this study is to determine the prevalence and predictors of contralateral risk-reducing mastectomy (CRRM) in Australasian women at high familial risk of a second primary breast cancer (BC). Participants were women with unilateral BC and a strong family history of the disease, including BRCA1/2 mutation carriers. Data were collected through interview, self-administered questionnaire and review of pathology and surgical reports. Associations between CRRM and potential predictors were assessed using multivariate logistic regression. Of 1,018 women (median follow-up 11.1 years), 154 (15%) underwent CRRM, 43% of these within 12 months of initial BC surgery. More likely to undergo CRRM were women who were younger at BC diagnosis (odds ratio [OR] = 0.94 per year of age, P < 0.001), were diagnosed more recently (OR = 1.16 per calendar year, P < 0.001), underwent mastectomy as initial definitive BC treatment (OR = 5.2, P < 0.001) and underwent risk-reducing salpingo-oophorectomy (OR = 3.4, P < 0.001). BRCA1/2 mutation status, axillary nodal status and receipt of chemotherapy were not independently associated with CRRM uptake. A contralateral BC event (invasive or in situ) occurred in 177 (20.5%) of the 864 women who did not have CRRM, compared with one chest wall event (0.6%) in the 154 women post-CRRM. The contralateral event rate was 15.1 per 1,000 women-years for non-CRRM women and 0.7 per 1,000 women-years for CRRM women; P < 0.0001. Younger women with more recently diagnosed BC treated with mastectomy are more likely to elect CRRM. Neither BRCA1/2 mutation status, nor the competing risk of BC recurrence and death, appears to influence decision making.