Multifocal breast cancers are more prevalent inBRCA2versusBRCA1mutation carriers

Abstract

Multifocal breast cancer is generally considered to be where two or more breast tumours are present within the same breast, but are clearly separated with no intervening in situ or invasive disease. It is seen in ~10% of breast cancer cases. This study investigates multifocality prevalence in BRCA1/2 mutant patients via cross-sectional analysis. Data from 211 women with BRCA1/2 mutations (91 BRCA1), (120 BRCA2), with breast cancer were collected including age, tumour focality, size, type, grade, and receptor profile. The prevalence of multifocality within this group was 25%, but within subgroups, prevalence amongst BRCA2 carriers was more than double that of BRCA1 carriers (p=0.001). Women affected by multifocal tumours had proportionately higher oestrogen receptor positivity (p=0.001), lower triple negativity (p=0.004), and were more likely to be younger at diagnosis compared with those with unifocal tumours (p=0.039). Odds of a BRCA2 carrier developing multifocal cancer were almost four-fold higher than a BRCA1 carrier (OR: 3.71, CI: 1.77 to 7.78, p=0.001). BRCA2 carriers show much greater multifocality than those carrying BRCA1. Multifocal tumours are strongly associated with being both BRCA2 mutant and oestrogen receptor positive.