Pregnancy reduces breast cancer risk in BRCA1/2 carriers

[unseennude]

Prior pregnancy reduces the risk of breast cancer in women older than 40 years who are carriers of BRCA1 or BRCA2 mutations, according to a report in the April 19th Journal of the National Cancer Institute.

Previous studies have shown an association between multiparity, young age at first childbirth, and breastfeeding and a reduced risk of breast cancer in the general population, the authors explain.

Dr. Nadine Andrieu from Institut Curie, Paris, France and colleagues investigated whether these factors reduced the risk of breast cancer in women participating in the International BRCA1/2 Carrier Cohort Study (IBCCS), which includes most of the large population-based studies of women carriers of BRCA1 and BRCA2 mutations.

Parous women had a slightly lower risk of breast cancer than nulliparous women, the authors report, but the difference was not statistically significant.

Among parous women older than 40 years, however, each additional birth reduced the risk of breast cancer an estimated 14%, the results indicate. The reduction in risk was similar for carriers of BRCA1 and BRCA2 mutations.

There were some differences between carriers of BRCA1 and BRCA2 mutations. Women with BRCA2 mutations who had their first pregnancy when they were 20 years or older had about twice the risk of breast cancer as women who had their first pregnancy when they were younger than 20 years.

On the other hand, the researchers note, women with BRCA1 mutations who had their first pregnancy when they were 20 years or older had a lower risk of breast cancer than women who had their first pregnancy when they were younger than 20 years.

There was no association between breast cancer risk and ever having breast fed, and no association between duration of breastfeeding and breast cancer risk, the report indicates.

"Our data provide evidence that multiple full-term pregnancies are associated with a moderate reduction in the risk of breast cancer in BRCA1 and BRCA2 mutation carriers, which is evident only in women older than 40 years," the authors conclude. "This decrease in breast cancer risk appears to be consistent with that found in the general population."