Comprehensive Genomic Characterization in Ovarian Low-Grade and chemosensitive and chemoresistant High-Grade Serous Carcinomas

Introduction: Genomic characterization of serous ovarian carcinoma (SOC), which includes low-grade serous carcinoma (LGSC) and high-grade serous carcinoma (HGSC), remains necessary to improve efficacy of platinum-based chemotherapy. The aim was to investigate the genomic variations in these SOC groups, also in relation to chemoresponse. Methods: 45 samples SOC were retrospectively analyzed by Next Generation Sequencing (NGS) on DNA/RNA extracts from formalin-fixed, paraffin-embedded (FFPE) tumor samples obtained at diagnosis. HGSCs were classified as platinum-resistant and platinum-sensitive. Results: In the LGSC group, 44% of the carcinomas had mutually exclusive variants in the RAS/RAF pathway, while additional likely oncogenic variants in the CDKN2A, SMARCA4 and YAP1 genes were observed in the remaining LGSCs. Tumor mutation burden (TMB) was significantly lower in the intrinsically chemoresistant LGSC group than in the HGSC group. In the HGSC cohort, TP53 variants were found in 90% and homologous recombination repair (HRR) pathway variants in 41% of the neoplasms. HGSCs of the chemoresistant group without classic mutations in the HRR pathway were characterized by additional variants in FGFR2 and with a FGFR3::TACC3 fusion. In addition, HGSCs showed MYC, CCNE1 and AKT2 gains that were almost exclusively observed in the chemosensitive HGSC group. Conclusions: These results suggest that very low TMB and MYC, CCNE1 and AKT2 gains in SOC patients may be biomarkers related to platinum treatment efficacy. Thorough genomic characterization of SOCs prior to treatment might lead to more specific platinum-based chemotherapy therapy strategies.