Effect of reproductive factors and lifestyle on the onset of breast cancer in female BRCA 1 and 2 mutation carriers.

1545 Background: We have recently demonstrated that the onset of breast cancer (BC) in BRCA 1 and 2 mutation carriers is influenced by their birth year, thus indicating a risk-modifying role for reproductive and life style factors. We now examined possible associations between potential risk factors, birth cohorts, and the onset of BC in BRCA1 and 2 mutation carriers. Methods: 130 female BRCA1 and 67 BRCA2 mutation carriers who had been identified at the Vienna University Hospital between 1995 and 2013, and who had developed BC were included in the analysis. Individual reproductive and life style factors were identified by questionnaires. Cox regression analysis and log-Rank testing were used to estimate the effect of potential risk factors on the onset of BC. Results: BRCA mutation carriers who had never been pregnant developed BC at a younger age than those who had been pregnant at least once (36.4 vs 40.9; p=0.001). Similarly, women who had used oral contraceptives, or had smoked, developed BC earlier ...