EGFR T790M Mutation in TKI-Naïve Clinical Samples: Frequency, Tissue Mosaicism, Predictive Value and Awareness on Artifacts.

Background: This study evaluated the distribution of epidermal growth factor receptor (EGFR) T790M mutations in treatment-naïve tumor and normal samples obtained from cancer patients.

Methods: We utilized allele-specific PCR (AS-PCR), digital droplet PCR (ddPCR) and next generation sequencing (NGS) to detect EGFR T790M allele in several collections of tumor and normal human tissues.

Results: AS-PCR analysis of treatment-naïve tumor samples revealed somatic T790M mutation in 3/394 (1%) non-small cell lung carcinomas (NSCLC) carrying the tyrosine kinase inhibitor (TKI)-sensitizing EGFR mutation, but in none of 334 NSCLC lacking EGFR exon 19 deletions (ex19del) or L858R substitutions and in none of 235 non-lung tumors.