Characteristics of EGFR uncommon mutations in Chinese cancer patients.

Abstract

e13527 Background: Exon 19 deletions and exon 21 L858R substitutions are the most common mutations of epidermal growth factor receptor (EGFR) in cancers, and the remaining other mutations are called uncommon mutations. Recent studies have shown the clinical relevance of EGFR uncommon mutations with tyrosine kinase inhibitors (TKI) therapies and immunotherapies. Therefore, understanding the distribution and characteristics of EGFR uncommon mutations in cancers would provide evidence for future design of trials and drug development. Methods: Next-generation sequencing data were obtained from 3,026 Chinese tumor samples which have been identified with EGFR mutations. Single nucleotide variations (SNV), short and long insertions/deletions (indel), copy number variations and gene rearrangements were assessed. All tests were carried out in a College of American Pathologists (CAP) accredited and Clinical Laboratory Improvement Amendments (CLIA) certified laboratory in Shanghai, China. Results: EGFR mutations including 32% L858R substitutions, 28% exon 19 deletions, and 40% uncommon mutations were detected in this cohort. EGFR uncommon mutations were most frequently detected in lung cancers, followed by esophageal and gastric cancers. The uncommon mutations of EGFR including 54% SNVs, 30% amplifications, and 9% rare types of mutations such as rearrangement, long indels and complex mutations were detected. The SNVs in exon 18 to 21 which encode the tyrosine kinase domain of EGFR consisted of 16% EGFR mutations. Among them, the mostly frequently SNV was G719X in exon 18 and had 3% EGFR mutations. Mutations in other function domain of EGFR, including extracellular EGF binding domain (0.8%), transmembrane domain (0.03%) and intracellular autophosphorylation domain (0.7%) were also detected. Conclusions: Our data indicated that EGFR uncommon mutations were widely distributed in a variety of cancer types in Chinese patients, mostly in lung cancers. SNVs in the tyrosine kinase domain were the most frequent uncommon mutations. These data will provide clues for future clinical studies.