Homologous recombination repair (HRR) is the cellular mechanism for error-free repair of DNA double-strand breaks. Pathogenic germline variants in BRCA1 and BRCA2 lead to HRR deficiency associated with breast, ovarian, prostate, pancreatic cancers and are sensitive to PARP inhibitors (PARPi). Defects in HRR genes beyond BRCA1/2 could also result in HRR deficiency and sensitize the tumor to PARPi, thus expanding...