Mucinous Histology Is Associated with Resistance to Anti-EGFR Therapy in Patients with Left-Sided RAS/BRAF Wild-Type Metastatic Colorectal Cancer

Abstract

Background: Limited studies have suggested that mucinous histology is associated an attenuated response to anti-epidermal growth factor receptor (EGFR) therapy. Methods: We conducted a single-institution, retrospective study to review the anti-EGFR response and the molecular profile of patients with left-sided microsatellite stable RAS/BRAF wild-type mucinous metastatic colorectal cancer. Results: In comparison to nonmucinous population (n = 98), mucinous histology (n = 20) was associated with a younger age (48 vs 54, P = .02), wild-type APC (80% vs 15.3%, P < .0001), and wild-type TP53 (40% vs 8.2%, P = .001). Guanine nucleotide binding protein, alpha stimulating (GNAS) mutations were exclusively found in mucinous tumors (20% vs 0, P