Reiner AS, et al. - In this update from the Women’s Environmental Cancer and Radiation Epidemiology (WECARE) study, which demonstrated the importance of breast cancer family history on contralateral breast cancer (CBC) risk, even for noncarriers of deleterious BRCA1/2 mutations, researchers describe updated risk estimates, with a report on additional analyses that excluded women negative for deleterious mutations in ATM, CHEK2*1100delC, and PALB2. As per findings, a high CBC risk was reported for subjects with breast cancer family history. This was noted even after excluding women with deleterious mutations. Clinicians are strongly recommended to use detailed family histories to guide treatment and future screening decisions for young women with breast cancer.

• A total of 1,521 CBC cases were compared with 2,212 individually matched unilateral breast cancer (UBC) controls in the WECARE Study, which is a population-based case-control study.
• Participants were younger than age 55 years when diagnosed with a first invasive breast cancer between 1985 and 2008.
• Interviews were carried out among women regarding breast cancer risk factors, including family history.
• Screening was performed in a subset of women for deleterious mutations in BRCA1/2, ATM, CHEK2*1100delC, and PALB2.
• Using multivariable conditional logistic regression, rate ratios (RRs) were estimated.
• By combining RRs from the WECARE Study and population-based SEER*Stat cancer incidence data, the cumulative absolute risks (ARs) were estimated.

• A 10-year AR of 8.1% for CBC was observed among women with any first-degree relative with breast cancer (95% CI, 6.7% to 9.8%).
• Researchers noted increased risks if the relative was diagnosed at an age younger than 40 years (10-year AR, 13.5%; 95% CI, 8.8% to 20.8%) or with CBC (10-year AR, 14.1%; 95% CI, 9.5% to 20.7%).
• It was also noted that these risks were comparable with those seen in BRCA1/2 deleterious mutation carriers (10-year AR, 18.4%; 95% CI, 16.0% to 21.3%).
• Findings demonstrated that estimates were unchanged in the subset of women who tested negative for deleterious mutations in BRCA1/2, ATM, CHEK2*1100delC, and PALB2.
• Data showed that adjustment for known breast cancer single-nucleotide polymorphisms did not affect estimates.