Germline Mutation of T790M and Dual/Multiple EGFR Mutations in Patients With Lung Adenocarcinoma

Introduction The epidermal growth factor receptor (EGFR) T790M mutation remains one of the major mechanisms of resistance to EGFR tyrosine kinase inhibitors (TKI) treatment. Cases of de novo EGFR T790M mutations prior to TKI treatment have been reported, but most of them were somatic mutations. In this study, we report a case of primary de novo dual EGFR mutations containing a germline T790M mutation in a NSCLC patient. We further describe a case series of NSCLC patients who had primary dual or multiple EGFR mutations. Methods EGFR mutation status was analyzed in 427 patients with lung adenocarcinomas. Clinical, demographic data and sequencing electropherograms were collected on patients with two or more EGFR mutations identified prior to EGFR TKI treatment. Peripheral blood mononuclear cells were sequenced for germ-line EGFR mutation on two patients with primary T790M mutation. Results 55 out of 427 (13%) patients with lung adenocarcinomas were found to have EGFR mutations; twelve of which were identified to have either dual or multiple EGFR mutations. Five of these 12 patients (42%) had primary de novo T790M mutation and three of them showed similar heights of the mutant and wild-type peaks on sequencing electropherogram, suggesting the possibility of germline mutation. One case of germline EGFR T790M mutation was confirmed via sequencing a peripheral blood sample. Conclusions Dual or multiple EGFR mutations comprised 2.8% of lung adenocarcinomas in our study. Primary de novo EGFR T790M mutation are presented with high frequency (5/12; 42%) in patients carrying dual or multiple EGFR mutations.