Concomitant EGFR mutation and EML4-ALK gene fusion in non-small cell lung cancer.

Abstract

10517 Background: The fusion of the anaplastic lymphoma kinase (ALK) with the echinoderm microtubule-associated protein-like 4 (EML4) and epidermal growth factor receptor (EGFR) mutations are considered mutually exclusive. Advanced non-small cell lung cancer (NSCLC) patients with EML4-ALK did not benefit from EGFR tyrosine kinase inhibitors (TKIs). Methods: Multiplex reverse transcriptase-polymerase chain reaction (RT-PCR) followed by sequencing was performed for EML4-ALK fusion status detection. EGFR and KRAS mutations were determined by direct DNA sequencing. Positive results of EML4-ALK fusion were also confirmed by RACE-coupled PCR sequencing. Results: From April 2010 to January 2011, 412 patients (398 with NSCLC; 14 with SCLC) were tested for mutation status of EGFR, KRAS and EML4-ALK respectively. Frequency of EML4-ALK fusion was 10.6% (42/398) in NSCLC patients. No patients with SCLC were found to have positive EML4-ALK fusion. Frequency of concomitant EGFR and EML4-ALK gene mutations was 1.0% (4/398) in NSCLC patients, and their variants of EML4-ALK gene mutations were Variant 1 (3 patients) and Variant 6 (1 patient); being never smokers, all of them were diagnosed with advanced (3 with stage ‡W and 1 with stage IIIB) adenocarcinoma harbouring wild type KRAS. Two female stage ‡W patients with double gene mutations (1 with L858R and Variant 1; 1 with exon19 deletion and Variant 6) received first-line gefitinib which is one kind of EGFR TKIs and achieved partial response. Conclusions: Though being rare events, NSCLC patients harbouring concomitant EGFR mutation and EML4-ALK gene fusion are sensitive to first-line EGFR TKIs. Whether they could also benefit from ALK inhibition after failure to EGFR TKIs warranted further investigation.