Role of c-MET pathway in the outcome prediction of cetuximab-based therapy in patients with recurrent or metastatic squamous cell carcinoma of the head and neck.

Abstract

5520 Background: Activation of the c-MET oncogene promotes tumor growth, invasion and metastasis in several tumor types. In addition, c-MET has been reported in consort with EGFR and/or be activated as a compensatory pathway in the presence of EGFR blockade resulting a mechanism of acquired resistance to EGFR inhibitors in lung and colorectal carcinoma. We investigated the impact on cetuximab sensitivity of HGF, c-MET, c-MET activation and c-MET gene status in recurrent or metastatic squamous cell carcinoma of the head and neck (HNSCC) patients. Methods: A single-institution retrospective analysis including 50 HNSCC patients was carried out. For each case, formalin-fixed tumor specimens were assayed for HGF, total and phosphorylated Y1234/35 c-MET (p-c-MET) by immunohistochemistry and c-MET gene by FISH. Overexpression criteria were defined by ROC curves for each protein and amplification was defined by >2 copies in at least two of the three studied tumor areas. Results were analyzed for association with clinico-pathological features and survival outcomes for cetuximab-treated patients (median follow-up 75 months). Results: c-MET overexpression was detected in 26 (52%) of patients, c-MET amplification in 15 (30%) and p-c-MET in 12 (24%). Amplification was associated with c-MET overexpression (p=0.004). HGF overexpression was observed in 8 (12%) associated with c-MET phosphorylation (p=0.001), suggesting a paracrine activation of receptor. No significant association with clinico-pathological parameters was detected. Log-rank test showed significantly worse outcome in c-MET overexpressing patients for progression-free (PFS) (p=0.002) and overall survival (OS) (p=0.045); p-c-MET was correlated with worse PFS (p=0.014) and OS (p<0.001). In multivariate logistic regression analysis, p-c-MET was an independent prognostic factor for PFS (HR 6.5; 95% CI 1.5-8.9). Conclusions: HGF/c-MET pathway correlated with worse outcome in cetuximab-based regimen treated HNSCC patients, acting as a resistance mechanism for EGFR inhibitors and supporting a dual blocking HGF/c-MET and EGFR pathways for treatment of these patients.