Contralateral breast cancer after radiotherapy among BRCA1 and BRCA2 mutation carriers: A WECARE Study Report

multi-national study - abstract

Findings

Among women treated with radiation, the mean radiation dose was 1.1 Gy (range = 0.02–6.2 Gy). Risk of developing CBC was elevated among women who carried a deleterious BRCA1/BRCA2 mutation (rate ratio, RR = 4.5, confidence interval, CI = 3.0–6.8), and also among those treated with RT (RR = 1.2, CI = 1.0–1.6). However, among mutation carriers, an incremental increase in risk associated with radiation dose was not statistically significant.

Interpretation

Multiplicative interaction of RT with mutation status would be reflected by a larger association of RT with CBC among carriers than among non-carriers, but this was not apparent. Accordingly, there was no clear indication that carriers of deleterious BRCA/BRCA2 mutations were more susceptible to the carcinogenic effects of radiation than non-carriers. These findings are reassuring and have important clinical implications for treatment decisions and the clinical management of patients harbouring deleterious BRCA1/BRCA2 mutations.