Association of alterations in DNA damage repair and Notch pathways with high tumor mutational burden in patients with cervical cancer.

e17511 Background: The outstanding efficacy of pembrolizumab reported in study KEYNOTE-158 led to FDA approval of pembrolizumab in the treatment of patients (pts) with positive PD-L1 expression (CPS ≥1) cervical cancer (CC) and tumor mutational burden-high [TMB-H, ≥10 mutations/megabase (mut/Mb)] solid tumors including CC. This study aims to investigate the immunotherapy-related molecular characteristics in pts with CC. Methods: The study recruited pts with CC whose tissues were send to perform parallel hybridization-based next-generation sequencing and/or immunohistochemistry of PD-L1 with 22C3 assay. KEGG pathway enrichment analysis was conducted to explore whether the differentiated mutated genes (DMGs) that were more frequently mutated in the TMB-H cohort were enriched in certain pathways. In addition, pair-wise comparison of TMB and PD-L1 was analyzed to identify the proportion of pts who might benefit from immunotherapy. Results: Among 249 pts with TMB evaluated, median TMB was 5 muts/Mb (range: 0 - 58.56 muts/Mb). The prevalence of microsatellite instability was 1.2% (3/255). The threshold of TMB was defined as 10 muts/Mb according to KEYNOTE-158. Consequently, 47 pts were considered as TMB-H and 202 pts were TMB-L. Regardless that TERC amplification was only found in the TMB-L group (9.5%, 19/202), Fisher’s exact test identified 98 genes with significantly higher alteration frequency in the TMB-H group compared with TMB-L group, including MLL2/3, TERT, PIK3CA, LRP1B, EP300 and ARID1A. Pathway enrichment analysis suggested that these DMGs were mainly enriched in mismatch repair, Notch, homologous recombination and Fanconi anemia pathways. There was no evident correlation between TMB and MSI (spearman r=0.2401, p=0.0101). The positivity rate of TMB or PD-L1 was 71.9%. Conclusions: Mutations in DNA damage repair and Notch pathways may explain TMB-H in pts with CC who might may serve as surrogate markers for TMB in CC.