Molecular profiling of metastatic colorectal tumors using nextgeneration sequencing: A single-institution experience

Background: Recent molecular characterization of colorectal tumors has identified several molecular alterations of interest that are considered targetable in metastatic colorectal cancer (mCRC). Methods: We conducted a single-institution, retrospective study based on comprehensive genomic profiling of tumors from 138 patients with mCRC using nextgeneration sequencing (NGS) via FoundationOne. Results: Overall, RAS mutations were present in 51.4% and RAF mutations were seen in 7.2% of mCRC patients. We found a novel KRASR^68S1 mutation associated with an aggressive phenotype. RAS amplifications (1.4% KRAS and 0.7% NRAS), MET amplifications (2.2%), BRAF^L597Ralterations (0.7%), ARAF^S214F alterations (0.7%), and concurrent RAS+RAF (1.4%), BRAF+RAF1 (0.7%), and rare PTEN-PIK3CA-AKT pathway mutations were identified and predominantly associated with poor prognosis. ERBB2 (HER2) amplified tumors were identified in 5.1% and all arose from the rectosigmoid colon. Three cases (2.2%) were associated with a hypermutated profile that was corroborated with findings of high tumor mutational burden (TMB): 2 cases with MSI-H and 1 case with a POLE mutation. Conclusions: Comprehensive genomic profiling can uncover alterations beyond the well-characterized RAS/RAF mutations associated with anti-EGFR resistance. ERBB2 amplified tumors commonly originate from the rectosigmoid colon, are predominantly RAS/BRAF wild-type, and may predict benefit to HER2-directed therapy. Hypermutant tumors or tumors with high TMB correlate with MSI-H status or POLE mutations and may predict a benefit from anti-PD-1 therapy.