BRCA1 and BRCA2 genetic mutation carriers older than 40 years display a similar reduction in breast cancer risk with increasing number of pregnancies carried to full-term, a risk parallel to that in the general population, according to a new study published in the Journal of the National Cancer Institute.

BRCA1 and BRCA2 mutations are known to increase a woman's risk of breast cancer. In women without the mutations, reproductive factors such as giving birth, young age at first childbirth, and history of breast-feeding are associated with a reduced risk of breast cancer, but few have studied those factors in women with these mutations.

Nadine Andrieu, Ph.D., of INSERM (Institute National de la Sante et de la Recherche Medical) at the Curie Institute in Paris, and colleagues retrospectively examined 1,601 women in the International BRCA1/2 Carrier Cohort Study (IBCCS) who had been asked about childbirth history, age at time of pregnancy, and breast-feeding habits. Of those women, 853 women had been diagnosed with breast cancer.

The authors found that there was no difference in risk of breast cancer between mutation-carrying women who had a full-term pregnancy and those who did not. Among women who had given birth, the risk of breast cancer for BRCA1 and BRCA2 mutation carriers decreased by 14% with each additional birth for women ages 40 and older. This decrease is similar to that found in the general population. The researchers also observed that first childbirth at age 20 years or older was associated with increased risk of breast cancer in BRCA2 mutation carriers. In BRCA1 mutation carriers, first childbirth at age 30 years or older was associated with decreased risk of breast cancer.

SOURCE:
Journal of the National Cancer Institute, April 19, 2006