Genomic overview of right-sided and left-sided colorectal cancer using comprehensive genomic sequencing.

e15101Background: Although the difference in right vs. left sidedness of colorectal cancer (CRC) in response to targeted therapy has been reported, we hypothesized that right-sided colorectal cancer (RCC) is more likely to have genetic alterations associated with resistance of anti-EGFR therapy. We tested this hypothesis using comprehensive genomic sequencing (CGS) on a set of samples from well-characterized CRC patients. Methods: Two-hundred-one primary colon cancer patients with either RCC or left-sided colorectal cancer (LCC) were analyzed. We investigated gene alterations using 415 gene panel, which includes the gene alterations associated with resistance of anti-EGFR therapy: TK receptors (ERBB2, MET, EGFR, FGFR1, and PDGFRA), RAS pathway (KRAS, NRAS, HRAS, BRAF, and MAPK2K1), and PI3K pathway (PTEN and PIK3CA). We defined the patients who had no alterations in any of the genes as “all wild-type”, who are theoretically considered as responders of anti-EGFR therapy. Other patients with genetic alterat...