Use of Family Relationships in Commercial Claims Data to Characterize Clinical Events of Patients with BRCA1/2 Cascade Testing.

BRCA1/2 genetic cascade testing has been studied in small-scale survey and controlled settings, but limited large-scale studies have been done because health records don't typically link family members. This study uses commercial claims data that connect family members on the same insurance plan to identify a large cohort of BRCA1/2 proband and cascade testers and characterizes their breast cancer screening and prevention service utilization. We identified 709 proband and 819 cascade testers. Consistent with clinical guidelines to test for a specific BRCA1/2 variant in a family, more cascade testers received known variant tests than proband testers. Also consistent with guidelines, more proband testers received BRCA1/2 testing after a breast cancer diagnosis compared to cascade testers, and more cascade testers had genetic counseling events pre-BRCA1/2 testing compared to proband testers. This technique and large BRCA1/2 genetic cascade testing cohort can open doors for new research.