Background: Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors have been introduced in the standard therapy of non-small-cell lung cancer (NSCLC), but they benefit a minority of patients. The study of molecular markers may identify the subset of patients who are the most appropriate to treat with these agents.
Methods: We analyzed 43 patients with advanced NSCLC who were treated with gefitinib, an oral EGFR tyrosine kinase inhibitor, were included in analysis. We evaluated EGFR in tumor tissue by using immunohistochemistry and fluorescence in situ hybridization. We also studied downstream molecules (AKT, ERK, p38 MAPK) and their activation status and the presence of EGFR mutations in tumor tissue in exons 18-21.
Results: Three patients had tumors with EGFR mutations, all of which had EGFR gene amplification with a ratio of 2 or greater (p= 0.001). There was no correlation between EGFR protein expression and gene amplification. Six patients (14%) achieved an objective response and nine (21%) had stable disease; the median survival was 162 days. EGFR mutations, high levels of AKT protein expression, rash of any grade, and no history of smoking were predictive of disease control (objective response plus stable disease). Only 3 of 15 patients (20%) with disease control had an EGFR mutation. On multivariate analysis, rash and AKT were independent predictors of disease control. Patients with rash survived longer than patients without rash.
Conclusions: EGFR mutation-positive tumors are present in a small fraction of patients who achieve disease control with gefitinib. Other molecular markers, such as AKT, need to be further evaluated. Clinical parameters remain major determinants of gefitinib activity in NSCLC.