Purpose: Homologous recombination DNA repair deficiency (HRD) is a therapeutic biomarker for sensitivity to platinum and poly(ADP-ribose) polymerase inhibitor therapies in breast and ovarian cancers. Several molecular phenotypes and diagnostic strategies have been developed to assess HRD; however, their clinical implementation remains both technically challenging and methodologically unstandardized.
Methods: We developed and validated an efficient and cost-effective strategy for HRD determination on the basis of calculation of a genome-wide loss of heterozygosity (LOH) score through targeted, hybridization capture and next-generation DNA sequencing augmented with 3,000 common, polymorphic single-nucleotide polymorphism (SNP) sites distributed genome-wide. This approach requires minimal sequence reads and can be readily integrated into targeted gene capture workflows already in use for molecular oncology. We interrogated 99 ovarian neoplasm-normal pairs using this method and compared results with patient mutational genotypes and orthologous predictors of HRD derived from whole-genome mutational signatures.
Results: LOH scores of ≥11% had >86% sensitivity for identifying tumors with HRD-causing mutations in an independent validation set (90.6% sensitivity for all specimens). We found strong agreement of our analytic approach with genome-wide mutational signature assays for determining HRD, yielding an estimated 96.7% sensitivity and 50% specificity. We observed poor concordance with mutational signatures inferred using only mutations detected by the targeted gene capture panel, suggesting inadequacy of the latter approach. LOH score did not significantly correlate with treatment outcomes.
Conclusion: Targeted sequencing of genome-wide polymorphic SNP sites can be used to infer LOH events and subsequently diagnose HRD in ovarian tumors. The methods presented here are readily generalizable to other targeted gene oncology assays and could be adapted for HRD diagnosis in other tumor types.