Molecular genetic testing in colon cancer: clinical aspects

Molecular genetic diagnostics is an essential element to plan for management of colorectal cancer (CRC) patients. The choice of systemic treatment for CRC is impossible without molecular testing of the tumor. For instance, the assessment of the KRAS and NRAS genes is mandatory for consideration of anti-EGFR agents. Tumors with BRAF V600E mutation are characterized by aggressive behavior, the necessity of intensive cytostatic regimens, as well as by sensitivity to combination therapy with BRAF and EGFR inhibitors. Inactivation of the DNA mismatch repair, the MUTYH gene or DNA polymerase epsilon (POLE) leads to an excessive tumor mutational burden; these CRC types are highly immunogenic and therefore respond to immune checkpoint inhibitors. Some colorectal carcinomas are characterized by overexpression of the HER2 oncogene, which make them sensitive to corresponding target therapies. There are CRCs with clinical signs of hereditary predisposition, which require germline genetic testing. Nowadays the molecular diagnosis of CRC is being seriously modified due to worldwide implementation of the next-generation sequencing (NGS) and hypersensitive variants of polymerase chain reaction, for example, droplet digital polymerase chain reaction (ddPCR). Non-invasive liquid biopsy is an example of another highly useful innovation that has growing importance for CRC screening, control of surgical intervention efficacy and monitoring of the disease course.