New research has shown differential associations of breast cancer (BCa) risk with parity in BRCA1 and BRCA2 mutation carriers, with higher risk for uniparous BRCA1 carriers and parous BRCA2 carriers.
The study, published in the Journal of the National Cancer Institute Cancer Spectrum, used weighted and time-varying Cox proportional hazards models to investigate whether reproductive events are associated with BCa risk for mutation carriers using a retrospective cohort of 5,707 BRCA1 and 3,525 BRCA2 mutation carriers and a prospective cohort of 2,276 BRCA1 and 1,610 BRCA2 mutation carriers.
Women with BRCA1 mutations who had two full-term pregnancies (FTPs) had a 21 per cent decreased risk of BCa compared with women with a single FTP. The risk was reduced by 30 per cent and 50 per cent in women who had three or at least four FTPs.
For BRCA2 mutation carriers, being parous was associated with a 30 per cent increased BCa risk and there was no apparent decrease in risk with multi-parity, except for having at least four FTPs versus one.
The authors say the findings might help to refine risk estimates and make it possible to adapt surveillance of mutation carriers according to their reproductive life history.