The association of genetic testing timing and mutation type on breast cancer management in patients with breast cancer-related mutations.

Background: We aim to characterize breast management for patients with genetic mutations and concurrent breast cancer (BC) or prior BC treatment.

Methods: Adults with a BC-related mutation and prior/concurrent BC diagnosis were identified. Groups were stratified by mutation type [BRCA1/2, high penetrance mutation (HPM), moderate penetrance mutation (MPM)] and timing of genetic testing (concurrent with BC versus after BC treatment). Outcomes were compared.

Results: Among 338 patients included, 63 ​% had BRCA1/2 mutations, 9 ​% HPM, and 28 ​% MPM. Approximately 38 ​% had testing concurrent with a BC diagnosis and 62 ​% after BC treatment. Patients with concurrent testing favored bilateral mastectomy (57 ​%) versus 26 ​% lumpectomy, and 16 ​% unilateral mastectomy, which varied by mutation type. Patients previously treated preferred surveillance (92 ​% vs. 8 ​% additional surgery), regardless of mutation type.

Conclusion: The timing of a significant BC-related genetic test result and mutation type may be associated with management decisions among patients with breast cancer.