Is there any predictor for clinical outcome in EGFR mutant NSCLC patients treated with EGFR TKIs?

Background: Tyrosine kinase inhibitors (TKIs) of the epidermal growth factor receptor (EGFR) have demonstrated some dramatic response rate and prolonged progression-free survival (PFS) in advanced non-small-cell lung cancer (NSCLC) patients with activating EGFR mutation. However, PFS and overall survival (OS) among those patients who were treated with EGFR TKIs are inconsistent and unpredictable. In this study, we evaluated predictors of clinical outcome in EGFR mutant NSCLC patients treated with EGFR TKIs. Methods: A total of 148 patients who had metastatic or recurrent NSCLC with activating EGFR mutation treated with either erlotinib or gefitinib as a first-line (n = 10) and a second-line or more treatment (n = 138) were retrospectively reviewed. Results: The median follow-up duration was 21.9 months (range, 1.1-62.5). The median PFS and OS for a total 148 patients were 10.6 months (95 % CI 9.0-12.2) and 21.8 months (95 % CI 18.5-25.1), respectively. The survival outcomes were similar between the first-line and second-line or more line of treatment of EGFR TKIs (P = 0.512 for PFS, P = 0.699 for OS). Although a high number of metastasis sites (3-6 vs. 1-2) were associated with shorter PFS and OS (median PFS 9.9 vs. 11.9 months, P = 0.019; median OS 16.4 vs. 22.2 months, P = 0.021, respectively) in univariate analysis, but not in multivariate analysis. According to the clinical and molecular markers by multivariate analysis, there were no significant differences in PFS. When PFS was dichotomized by median 11 months for 105 patients treated with EGFR TKIs as second-line therapy, no significant differences in any clinical or molecular features were found between longer PFS and shorter PFS groups. Conclusions: Despite the inconsistencies in PFS among EGFR mutant patients treated with EGFR TKIs, no significant differences of clinical features were noted, thereby suggesting a need for more understanding of the heterogeneity of underlying biology.