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Homologous recombination deficiency (HRD) is characterized by the inability of a cell to repair the double-stranded breaks using the homologous recombination repair (HRR) pathway. The deficiency of the HRR pathway results in defective DNA repair, leading to genomic instability and tumorigenesis. The presence of HRD has been found to make tumors sensitive to ICL-inducing platinum-based therapies and poly(adenosine diphosphate [ADP]–ribose) polymerase (PARP) inhibitors (PARPi). However, there are no standardized methods to measure and report HRD phenotypes. Herein, we compare optical genome mapping (OGM), chromosomal microarray (CMA), and a 523-gene NGS panel for HRD score calculations. This retrospective study included the analysis of 196 samples, of which 10 were gliomas, 176 were hematological malignancy samples, and 10 were controls. The 10 gliomas were evaluated with both CMA and OGM, and 30 hematological malignancy samples were evaluated with both the NGS panel and OGM. To verify the scores in a larger cohort, 135 cases were evaluated with the NGS panel and 71 cases with OGM. The HRD scores were calculated using a combination of three HRD signatures that included loss of heterozygosity (LOH), telomeric allelic imbalance (TAI), and large-scale transitions (LST). In the ten glioma cases analyzed with OGM and CMA using the same DNA (to remove any tumor percentage bias), the HRD scores (mean ± SEM) were 13.2 (±4.2) with OGM compared to 3.7 (±1.4) with CMA. In the 30 hematological malignancy cases analyzed with OGM and the 523-gene NGS panel, the HRD scores were 7.6 (±2.2) with OGM compared to 2.6 (±0.8) with the 523-gene NGS panel. OGM detected 70.8% and 66.8% of additional variants that are considered HRD signatures in gliomas and hematological malignancies, respectively. The higher sensitivity of OGM to capture HRD signature variants might enable a more accurate and precise correlation with response to PARPi and platinum-based drugs. This study reveals HRD signatures that are cryptic to current standard of care (SOC) methods used for assessing the HRD phenotype and presents OGM as an attractive alternative with higher resolution and sensitivity to accurately assess the HRD phenotype.

The standard-of-care (SOC) for genomic testing of myeloid cancers primarily relies on karyotyping/fluorescent in situ hybridization (FISH) (cytogenetic analysis) and targeted gene panels (usually ≤54 genes) that harbor hotspot pathogenic variants (molecular genetic analysis). Despite this combinatorial approach, ~50% of myeloid cancer genomes remain cytogenetically normal, and the limited sequencing variant profiles obtained from targeted panels are unable to resolve the molecular etiology of many myeloid tumors. In this study, we evaluated the performance and clinical utility of combinatorial use of optical genome mapping (OGM) and a 523-gene next-generation sequencing (NGS) panel for comprehensive genomic profiling of 30 myeloid tumors and compared it to SOC cytogenetic methods (karyotyping and FISH) and a 54-gene NGS panel. OGM and the 523-gene NGS panel had an analytical concordance of 100% with karyotyping, FISH, and the 54-gene panel, respectively. Importantly, the IPSS-R cytogenetic risk group changed from very good/good to very poor in 22% of MDS (2/9) cases based on comprehensive profiling (karyotyping, FISH, and 54-gene panel vs. OGM and 523-gene panel), while additionally identifying six compound heterozygous events of potential clinical relevance in six cases (6/30, 20%). This cost-effective approach of using OGM and a 523-gene NGS panel for comprehensive genomic profiling of myeloid cancers demonstrated increased yield of actionable targets that can potentially result in improved clinical outcomes.