Cytokeratin 19 Fragment Predicts the Efficacy of Epidermal Growth Factor Receptor-Tyrosine Kinase Inhibitor in Non-Small-Cell Lung Cancer Harboring EGFR Mutation

Background: EGFR gene mutation is independently associated with a favorable response in non-small-cell lung cancer (NSCLC) patients receiving epidermal growth factor receptor -tyrosine kinase inhibitors (EGFR-TKIs), regardless of sex or smoking history. Squamous cell carcinoma patients harboring EGFR mutations show a significantly worse response to EGFR-TKIs compared with adenocarcinoma patients. We hypothesized that the serum cytokeratin 19 fragment (CYFRA 21-1) is associated with the efficacy of EGFR-TKIs in EGFR-mutated NSCLC patients. Methods: We retrospectively screened 160 NSCLC patients harboring EGFR mutations, who had received either gefitinib, or erlotinib between 1992 and 2011. Patients were screened for clinical characteristics, the efficacy of EGFR-TKI, and tumor markers (carcinoembryonic antigen [CEA]/CYFRA 21-1) at the initial diagnosis. Results: Of 160 eligible patients treated with EGFR-TKIs, 77 patients with high CYFRA 21-1 level (>2 ng/ml) showed significantly shorter progression-free survival (PFS) than the 83 patients with normal CYFRA 21-1 level (median PFS, 7.5 versus 13.3 months; p < 0.001). No significant difference in PFS was observed between the high-CEA group (>5 ng/ml) and the normal-CEA group (median PFS, 8.6 versus 11.2 months; p = 0.242). A multivariate analysis revealed that high CYFRA 21-1 level is independently associated with PFS (hazard ratio, 1.27; p = 0.002). No significant difference in overall survival was observed between the high- and the normal-CYFRA 21-1 groups (median overall survival, 24.8 versus 39.1 months; p = 0.104). Conclusions: Patients with a high CYFRA 21-1 level have significantly shorter PFS. CYFRA 21-1 is not a prognostic but a predictive marker of EGFR-TKI treatment in EGFR-mutated NSCLC patients.