Breast Cancer Risk in Women With BRCA Mutations: Role of Number of Pregnancies
Posted: Monday, April 29, 2019
The lower risk of breast cancer associated with women with multiple pregnancies and breastfeeding in the general population may also be extended to women with the highest risk of breast cancer, according to findings presented in JNCI Cancer Spectrum. Findings suggest differential associations with parity between BRCA1 and BRCA2 mutation carriers with a higher risk for uniparous BRCA1 mutation carriers and parous BRCA2 mutation carriers, observedd Mary Beth Terry, PhD, of the Mailman School of Public Health at Columbia University and the Herbert Irving Comprehensive Cancer Center, New York, and colleagues.
“What we have learned is that timing really matters for many risk factors, and the dual effect of pregnancy we see in nonmutation carriers with a long-term protection but short-term increase following a pregnancy may not extend to all women with BRCA1 and BRCA2 mutations,” Dr. Terry said in a press release.
Researchers investigated whether reproductive events were associated with breast cancer risk for mutation carriers using data from the largest international cohort study of BRCA1 and BRCA2 mutation carriers to date. The cohort included 5,707 BRCA1 and 1,610 BRCA2 mutation carriers.
Dr. Terry and colleagues found no overall association with parity for BRCA1 mutation carriers compared with nulliparity (hazard ratio = 0.99). Relative to being uniparous, an increased number of full-term pregnancies was associated with a decreased breast cancer risk (hazard ratio = 0.79), whereas an increasing duration of breastfeeding was associated with decreased breast cancer risk in the prospective analysis (hazard ratio = 1.69).
For BRCA2 mutation carriers, being parous was associated with a 30% increase in breast cancer risk (hazard ratio = 1.33), with no apparent decrease in risk associated with multiparity, except for having at least 4 full-term pregnancies compared with 1 full-term pregnancy (hazard ratio = 0.72).
Disclosure: The study authors’ disclosure information may be found at academic.oup.com.