EGFR-TKI benefit for NSCLC patients with EML4-ALK rearrangement.

Abstract

e18035 Background: EML4-ALK rearrangement defines a new molecular subtype of non-small-cell lung cancer (NSCLC). To identify the biological profiles of these patients, we examined the clinico-pathologic characteristics and treatment outcomes of NSCLC patients based on EML4-ALK and EGFR mutations. Methods: Patients with stage IV NSCLC were screened for EML4-ALK rearrangement and EGFR mutations at Peking University Cancer Hospital. EML4-ALK was identified using fluorescent in situ hybridization (FISH) confirmed by immunohistochemistry (IHC), and EGFR mutations were determined using denaturing high-performance liquid chromatography (DHPLC). Results: Of the 151 patients screened, 113 had complete follow-up data as an analysis set. The incidence of EML4-ALK was 9.7% (11/113) using FISH, in which 10 cases had sufficient specimens for IHC confirmation and all were positive. Overall, EML4-ALK and EGFR mutations were largely mutually exclusive (p = 0.033), although two patients harbored concurrent mutations. EML4-ALK rearrangement was associated with resistance to EGFR-TKIs compared with the EGFR mutant type and WT/Nonrearrangement type (p = 0.001 for objective response rate; p = 0.004 for disease control rate; p = 0.021 for progression-free survival [PFS]). In terms of patients who received platinum-based doublet chemotherapy, no significant differences were observed in PFS between the EML4-ALK type, EGFR mutant type, and WT/Nonrearrangement type. Moreover, two patients with concurrent EML4-ALK and EGFR mutations had superior PFS after EGFR-TKI compared with single EML4-ALK-rearranged patients. Conclusions: This study presents several biological features of EML4-ALK NSCLC. It is largely mutually exclusive to EGFR mutations, resistant to EGFR-TKI. Coexistence of ALK rearrangement and EGFR mutation in patients with advanced NSCLC might represent a separate genotype with unique biological characteristics.