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ObjectiveOlaparib plus bevacizumab maintenance therapy improves survival outcomes in women with newly diagnosed, advanced, high-grade ovarian cancer with a deficiency in homologous recombination. We report data from the first year of routine homologous recombination deficiency testing in the National Health Service (NHS) in England, Wales, and Northern Ireland between April 2021 and April 2022.MethodsThe Myriad myChoice companion diagnostic was used to test DNA extracted from formalin-fixed, paraffin-embedded tumor tissue in women with newly diagnosed International Federation of Gynecology and Obstetrics (FIGO) stage III/IV high-grade epithelial ovarian, fallopian tube, or primary peritoneal cancer. Tumors with homologous recombination deficiency were those with aBRCA1/2mutation and/or a Genomic Instability Score (GIS) ≥42. Testing was coordinated by the NHS Genomic Laboratory Hub network.ResultsThe myChoice assay was performed on 2829 tumors. Of these, 2474 (87%) and 2178 (77%) successfully underwentBRCA1/2and GIS testing, respectively. All complete and partial assay failures occurred due to low tumor cellularity and/or low tumor DNA yield. 385 tumors (16%) contained aBRCA1/2mutation and 814 (37%) had a GIS ≥42. Tumors with a GIS ≥42 were more likely to beBRCA1/2wild-type (n=510) thanBRCA1/2 mutant (n=304). The distribution of GIS was bimodal, withBRCA1/2mutant tumors having a higher mean score thanBRCA1/2wild-type tumors (61 vs 33, respectively, χ2test pConclusionThis is the largest real-world evaluation of homologous recombination deficiency testing in newly diagnosed FIGO stage III/IV high-grade epithelial ovarian, fallopian tube, or primary peritoneal cancer. It is important to select tumor tissue with adequate tumor content and quality to reduce the risk of assay failure. The rapid uptake of testing across England, Wales, and Northern Ireland demonstrates the power of centralized NHS funding, center specialization, and the NHS Genomic Laboratory Hub network.

OBJECTIVE To determine the frequency of germline and somatic pathogenic BRCA1 and BRCA2 variants in patients with high-grade serous ovarian cancer tested by next-generation sequencing (NGS), with the aim of defining the best strategy to be implemented in future routine testing. DESIGN National retrospective audit. SETTING The All Wales Medical Genomics Service (AWMGS). POPULATION Patients with high-grade serous ovarian/fallopian tube/peritoneal cancer referred by oncologists to the AWMGS between February 2015 and February 2021 for germline and/or tumour testing of the BRCA1 and BRCA2 genes by NGS. METHODS Analysis of NGS data from germline and/or tumour testing. MAIN OUTCOME MEASURES Frequency of BRCA1 and BRCA2 pathogenic variants. RESULTS The overall observed germline/somatic pathogenic variant detection rate was 11.6% in the 844 patients included in this study, with a 9.2% (73/791) germline pathogenic variant detection rate. Parallel tumour and germline testing was carried out for 169 patients and the overall pathogenic variant detection rate for this cohort was 14.8%, with 6.5% (11/169) shown to have a somatic pathogenic variant. Two BRCA1 dosage variants were found during germline screens, representing 2.0% (2/98) of patients with a pathogenic variant that would have been missed through tumour testing alone. CONCLUSIONS Parallel germline and tumour BRCA1 and BRCA2 testing maximises the detection of pathogenic variants in patients with high-grade serous ovarian cancer. TWEETABLE ABSTRACT Parallel germline and tumour testing maximises BRCA pathogenic variant detection in ovarian cancer.