Two patients (EGFR A763_Y764insFQEA and EGFR T751_I759>S) had received erlotinib during their treatment course and both of them showed stable disease with a progression-free survival of 5.9 and 10.1 months, respectively...The most overlooked mutations were exon 20 insertions. A comprehensive EGFR mutation assay can provide significant benefit to NSCLC patients, especially in an area with a high prevalence of EGFR mutations.