Abstract
Background: Poly(adenosine diphosphate [ADP]-ribose) polymerase inhibitors (PARPis) are indicated for treatment of tumors with breast cancer susceptibility genes BRCA1/2 mutations and homologous recombination deficiency (HRD). Little is known about differences in care by BRCA1/2 and HRD status for breast and ovarian cancers.

Methods: We investigated clinical characteristics, treatment, clinical outcomes, and health-care resource utilization by BRCA1/2 or HRD status among patients diagnosed between 2018-2020 with HER2-negative metastatic breast (mBC) and advanced epithelial ovarian cancer (aEOC) in the United States community healthcare setting.

Results: The study included 314 patients with mBC and 465 with aEOC. Patients with mBC carrying a BRCA1/2 mutation were younger and had a higher proportion of triple negative cancer than non-carriers (50% vs 38%). Only 8% of eligible patients received a PARPi in first-line (1L) and 18% in second-line (2L) of treatment for mBC. In aEOC, patients with HRD were younger and a higher proportion received 1L maintenance treatment with a PARPi than patients with non-HRD tumors (95% vs 66%). In aEOC, patients without HRD had greater healthcare resource use. Patients with BRCA-mutated tumors had poorer overall survival (OS); there were no differences in OS by HRD status in aEOC.

Conclusion: This study demonstrated differences in treatment by BRCA1/2 and HRD status. There was low PARPi uptake among patients with BRCA-mutated mBC but not among patients with aEOC. In aEOC, the cost to “treat all” may outweigh benefits; identifying patients without HRD likely to benefit from PARPis is needed.

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