Is There a Role for IGF1R and c-MET Pathways in Resistance to Cetuximab in Metastatic Colorectal Cancer?

BackgroundThe KRAS mutation is not responsible for all cases of resistance to anti–epidermal growth factor receptors (EGFRs) in metastatic colorectal cancer (mCRC), and new predictive and prognostic factors are actively being sought.Patients and MethodsWe retrospectively evaluated the efficacy of a cetuximab-containing treatment in 73 patients with mCRC according to KRAS and BRAF mutational status as well as PTEN, c-MET, and insulin-like growth factor receptor (IGF1R) expression.ResultsOverall response rate (ORR), median progression-free survival (mPFS), and median overall survival (mOS) were significantly lower in patients with KRAS mutation than in patients with KRAS wild-type; among the population with KRAS wild-type, only 2 patients with BRAF mutations were found and neither of them achieved a response. No significant association was found between PTEN and clinical outcome. Compared with low/normal expression, c-MET overexpression significantly correlated with shorter mPFS and mOS: 3 vs. 5 months (P = .018) and 11 vs. 10 months (P = .037), respectively. In patients with high IGF1R expression, mOS was significantly longer than in those with low/normal expression (14 vs. 8 months; P = .015).ConclusionKRAS mutation significantly correlates with a worse outcome in patients treated with cetuximab, whereas no definitive inference can be drawn about the role of BRAF mutation and PTEN loss of expression. Instead, c-MET overexpression might represent a negative prognostic factor in mCRC and may have a role in resistance to anti-EGFR therapy. Interestingly, IGF1R overexpression seems a favorable prognostic factor in mCRC.