Comprehensive molecular analysis to predict the efficacy of chemotherapy containing bevacizumab in patients with metastatic colorectal cancer

Background: Although bevacizumab is an important treatment for metastatic colorectal cancer (CRC), not all patients with CRC benefit from it; in unselected patient populations, only modest survival benefits have been reported.Methods: We evaluated clinical outcomes in 110 patients using comprehensive molecular characterization to identify biomarkers for a response to bevacizumab-containing treatment. The molecular analysis comprised whole-exome sequencing, ribonucleic acid sequencing, and a methylation array on patient tissues.Results: Genomic and molecular characterization was successfully conducted in 103 patients. Six of 103 CRC samples were hypermutated, and none of the non-hypermutant tumors were microsatellite unstable. Among those 103 patients, 89 had adenocarcinoma (ADC), 15 were diagnosed with mucinous ADC, and six had signet-ring cell carcinoma (SRCC). Consensus molecular subtype (CMS) 2 was unique to ADC. Of the four SRCCs, two were CMS1, one was CMS4, and the other was CMS3. APC mutation status was a significantly enriched factor in responders to bevacizumab treatment. Fibroblast growth factor receptor (FGFR) 1/2 signaling was upregulated in non-responders, whereas cell cycle, transfer ribonucleic acid processing, nucleotide excision repair, and oxidative phosphorylation pathways were enriched in responders. In addition, IGF1 was differentially expressed in non-responders (log2 fold change=-1.43, p=4.11 x 10-5, false discovery rate=0.098), and FLT1 was highly methylated in non-responders (p=7.55 x 10-3). When the molecular pathways were reanalyzed separately according to the backbone chemotherapy (FOLFOX vs. FOLFIRI), the significance of the molecular pathways varied according to the backbone chemotherapy.Conclusions: This study sought a subset of CRC patients with a distinct clinical response to chemotherapy containing bevacizumab. Our results need to be validated in a large group of homogenous patient cohort and examined according to the different chemotherapy backbones to create personalized therapeutic opportunities in CRC.