Prognostic impact of tumor MET expression among patients with stage IV gastric cancer: A Danish cohort study.

Abstract

43 Background: Recent clinical trial data indicate poor prognosis for patients with late-stage gastric cancer and positive tumor mesenchymal epithelial transition factor (MET) protein expression. However, there is limited information about the real-world prevalence of MET-positive (-pos) cancers and the associated prognosis. Methods: Using medical registries, we identified a cohort of patients with stage IV gastric cancer in a single institution in Northern Denmark from 2003-2010. From these patients, we collected archived (paraffin-embedded) cancer specimens and analyzed MET protein expression by immunohistochemistry (MET-pos if ≥25% of tumor cells showed membrane staining). We calculated the prevalence of patients with MET-pos tumors. We estimated survival using the Kaplan-Meier method and computed mortality rate ratios comparing MET-pos to MET-negative (-neg) patients using Cox proportional hazards models adjusted for age, gender, and Charlson’s Comorbidity Index (score of 0, 1-2, and 3+). Results: 101 patients with stage IV gastric cancer were included in the study of which 55% had MET-pos tumors. The group of patients with MET-pos tumors were younger at diagnosis than patients with MET-neg tumors (median age 65 vs 68 years), included more men, showed higher comorbidity levels, included more poorly differentiated cancers, and were less likely to undergo surgery or chemotherapy. In patients with MET-pos tumors, one-year survival was 18% compared to 39% in patients with MET-neg tumors (mortality rate ratio=2.3, 95% CI: 1.4-3.9). Conclusions: A large proportion of patients with stage IV gastric cancer had tumors demonstrating MET protein expression, and these patients had poor survival compared with patients without tumor MET expression. [Table: see text]