MET Amplification Is Not Rare and Predicts Unfavorable Clinical Outcomes in Patients With Recurrent/Metastatic Gastric Cancer After Chemotherapy

BACKGROUND Several large studies have reported an extremely low incidence of MET gene amplification (GA) in patients with radically resected gastric cancer. This study was conducted to evaluate the prevalence and prognostic role of MET in patients with recurrent/metastatic gastric cancer who received chemotherapy. METHODS MET GA and protein expression of recurrent/metastatic gastric cancer samples were evaluated by fluorescence in situ hybridization and immunohistochemistry (IHC), respectively. RESULTS This retrospective study included 232 patients with recurrent/metastatic gastric cancer. MET GA and strong protein expression (IHC3+) were observed in 8.3% (19 of 230 samples) and 9.6% (22 of 229 samples) of samples, respectively. A significant correlation was observed between MET GA and protein expression (r = 0.378; P <.001). MET GA was correlated with poor performance status (P <.001) and poorly differentiated tumors (P =.0015). Both MET GA and IHC 3+ expression were associated with a substantially shorter median overall survival (OS) and progression-free survival (PFS). The median OS and PFS for patients with MET GA versus those without MET GA were 5.7 months versus 15.5 months (P <.001) and 3.6 months versus 6.9 months (P <.001), respectively. The median OS and PFS for patients with MET IHC 3+ expression versus IHC 0 to 2+ expression were 6.3 months versus 15.1 months (P <.001) and 3.6 months versus 7.0 months (P <.001), respectively. CONCLUSIONS In patients with recurrent/metastatic gastric cancer, MET amplification and strong protein expression are not rare and appear to be significantly associated with unfavorable clinical outcomes. © 2013 American Cancer Society.