B-390 Next-generation Sequencing Panel to Detect Homologous Recombination Deficiency (HRD) Biomarkers in Brazilian Ovarian Cancer Samples

Abstract

Abstract Background Homologous recombination deficiency (HRD) has been used as a biomarker of PARP inhibitors (PARPi) sensitivity in ovarian cancer (OC), especially in high-grade serous (HGS) types. Initially, only likely pathogenic (LPV) and pathogenic variants (PV) in BRCA1/2 were screened to define PARPi eligibility. However, LPV and PV are shown in less than 20% of OC, which restricted PARPi therapies to a small group. Advances in OC biology knowledge identified other markers that also contribute to HRD. Nowadays, is estimated that almost 50% of OC have HRD. When HRD is present, DNA damage is not properly repaired and the accumulated genomic changes over time are called Genomic Scars (GS). In this sense, Next Generation Sequencing (NGS) is important in GS detection due to searching different loci simultaneously, allowing an estimate of the GS score related to the HRD. So, this work aims to describe the profile of samples requesting an NGS test to detect HRD biomarkers. Methods Were evaluated anonymized data of 76 formalin-fixed, paraffin-embedded (FFPE) samples with OC diagnosis. The samples’ quality was evaluated with TapeStation 4200 and Qubit Fluorometer. Libraries were prepared with AmoyDx® HRD Focus Kit and sequenced with NextSeq 500. Data analysis was performed with ANDAS software. Results The HRD-positive percentage was 59,2% (45/76), being mostly BRCA wild type. Almost 15% of all samples presented PV or LPV in BRCA1 or 2, which was more frequent in BRCA1 (∼82%). The allele frequencies (AF) detected ranged from 5% to 83%. Two of the detected variants (classified as LPV) are not yet registered in databases. The HRD-negative group represented 34,2% (26/76), and 6,6% of performed tests had inconclusive results. Some requests (data not included) were not performed due to insufficient material, low quality, or FFPE block age greater than two years, which are limiting factors of this kind of test. Conclusion The availability of validated HRD testing options is essential to extend the reach to patients who may benefit from PARPi. In this analysis, most of the BRCA1/2 PV or LPV had AF above 50%, which can help oncologists to suggest germline PV investigation for these patients and also their families. Besides, our data showed a slightly higher HRD-positive rate than reported in the literature, although other works have already described rates above 60%. It reinforces the importance to monitor the HRD status of Brazilian samples to obtain a more assertive profile to the clinical practice.