Use of homologous recombination deficiency (HRD) score to enrich for niraparib sensitive high grade ovarian tumors.

5532 Background: The therapeutic potential of PARP inhibitors is predicted to extend beyond patients with germline BRCA mutations (BRCAmut) to those with homologous recombination deficient (HRD) cancers. An HRD test is being applied to patient samples to identify BRCA mutated tumors, provide a categorical determination of tumor HRD, and determine an enrichment strategy for patients with tumors that are sensitive to niraparib treatment. Methods: Archival FFPE tumor tissue obtained from ovarian cancer patients enrolled in an ongoing Phase III clinical study (ENGOT-OV16/NOVA, NCT 01847274) and a living tumor bank was subjected to HRD testing. The final HRD score is a numeric output ranging from 0-100. A predefined cut-off score of 42 was utilized to determine HRD status of each tumor and classify it as HR deficient (HRD score ≥ 42) or non-deficient (HRD score < 42). Classification of BRCA mutations from tissue was based on analysis criteria consistent with the laboratory’s approved diagnostic BRCA testing. N...