Importance of Early Next-Generation Sequencing in Microsatellite Unstable Colon Cancer With a High Tumor Mutation Burden.

Colon cancer is one of the leading causes of cancer-related deaths. Microsatellite instability (MSI) or deficient mismatch repair proteins with a high tumor mutation burden (TMB) colon cancer are less responsive to chemotherapy. Targeted therapies based on early next-generation sequencing (NGS) in metastatic colon cancer can help significantly in overall prognosis. Here, we report a case of colon cancer that illustrated significant TMB and MSI and responded poorly to treatment due to delay in NGS testing.