Homologous recombination pathway alternations in relation to prognosis of MSS/pMMR colorectal cancer patients treated with immune checkpoint inhibitors (ICIs).

Abstract

e15517 Background: Colorectal cancer is a common malignant tumor in the gastrointestinal tract and represents the third deadliest cancer worldwide. Recently, the advent of immune checkpoint inhibitors (ICIs) has provided significant survival benefit for colorectal cancer(CRC) patients with MSI-H/dMMR. However, the majority of MSS/pMMR CRC patients show poorly durable responses of immunotherapy, and more proper predictive biomarker is required to guiding immunotherapy treatment for these CRC cancer patients. The purpose of the present study was to explore the role of Homologous recombination (HR) pathway alternations in predicting the prognosis of MSS/pMMR CRC patients treated with ICIs. Methods: All data of patients undergoing immunotherapy were obtained from the cBioPortal database (https://www. cbioportal.org), which include genomic sequencing datasets and clinical data for eight diverse cancers from MSKCC, and RNAseq data and clincial data for CRC from International Cancer Genome Consortium (TCGA). Results: In the MSKCC cohort, HR mutation was analyzed by univariate Cox regression in nine different cancers, the analysis performed revealed HR mutation were associated with a better prognosis of colcrectal cancer (p = 0.003; HR, 0.24; 95%Cl, 0.09-0.62) and melanoma (p = 0.042; HR,0.66; 95% Cl, 0.09-0.62), with no significant correlations in other cancers. By doing survival analysis of the CRC patients without MSI-H/dMMR status by Kaplan–Meier (KM) method. The results showed that the OS of the patients with HR-MT was signifcantly longer than that of patients with HR-WT (P = 0.0029), and no significance association has been identified between Tumor Mutational Burden (TMB) and overall prognosis of patients without MSI-H/dMMR. Notably, in TCGA CRC dataset, we found TMB and Neoantigens were significantly higher in HR-MT patients than that of HR-WT patients(p < 0.0001), and a higher-level expression of CD8 T cell were also observed in the HR-MT patients patients in TCGA dataset (p = 0.036). Conclusions: Our study results showed that HR-mutation is a favorable prognostic factor in these CRC patients with MSS/pMMR, which can be used as a potential biomarker for predicting the immunotherapy efficacy of these patients.