Clinical Predictors of Response to EGFR Tyrosine Kinase Inhibitors in Patients with EGFR-Mutant Non-Small Cell Lung Cancer

BACKGROUND: The presence of EGFR (epidermal growth factor receptor) mutations is a robust predictor of EGFR tyrosine kinase inhibitor (TKI) responsiveness. Predictors of EGFR-TKI responsiveness in EGFR-mutant non-small cell lung cancer (NSCLC) patients, however, have not been well investigated. The purpose of this study is to examine predictors of EGFR-TKI responsiveness in EGFR-mutant NSCLC patients. PATIENTS AND METHODS: Seventy EGFR-mutant NSCLC patients who received EGFR-TKIs in our institution between April 2007 and March 2013 were analyzed retrospectively. RESULTS: The objective response rate was 50.0% (95% confidence interval, CI, 38.6-61.4%) and the disease control rate was 91.4% (95% CI, 82.5-96.0%). The median progression-free survival (PFS) and overall survival were 9.0 (95% CI, 3.92-14.08) and 20.8 months (95% CI, 14.56-27.04), respectively. In multivariate analysis, adenocarcinoma (hazard ratio, HR, 12.25; 95% CI, 37.7-41.10; p < 0.001) and major mutations (deletions in exon 19 and L858R point mutation in exon 21; HR, 2.46; 95% CI, 1.14-5.28; p = 0.022) were significant predictors of longer PFS. CONCLUSION: Major mutations and adenocarcinoma histology were independent predictors of better treatment outcome in EGFR-mutant NSCLC patients who received EGFR-TKIs. Further well-controlled prospective studies are warranted to confirm our findings.