Characterisation of homologous recombination deficiency in paired primary and recurrent high-grade serous ovarian cancer

Background Homologous recombination deficiency (HRD) is shown to predict response to DNA-damaging therapies in patients with high-grade serous ovarian cancer (HGSOC); however, changes in HRD during progression remains unknown. Methods HRD scores were evaluated in paired primary and/or recurrent HGSOC samples ( N = 107) from 54 patients with adjuvant platinum-based chemotherapy. BRCA1/2 mutation, BRCA1 methylation, loss of heterozygosity (LOH), and HRD scores were characterised using tumour DNA-based next-generation sequencing assays. Results Among 50 evaluable pairs ( N = 100 samples), high intra-patient correlation in HRD score was observed ( r 2 = 0.93). BRCA1/2 mutations, BRCA1/2 LOH, and HRD were maintained between primary and recurrent samples, except for one pair in which a BRCA1 reversion mutation was identified in the recurrent sample. Despite the reversion, both samples were classified as having high HRD scores ( ≥ 42). All samples with BRCA1 /2 mutations exhibited high HRD scores; however, high HRD scores were more prevalent than BRCA1 /2 mutations (55% vs. 30%, respectively). Conclusion Markers of HRD were maintained between the primary and recurrent samples, regardless of other genomic changes that occurred during recurrence. HRD score/markers in primary tumours may be valuable and adequate for selection of platinum-based therapy and/or poly-ADP-ribose-polymerase (PARP) inhibitors in recurrent HGSOC.