Detection of EGFRexon 20 insertion mutations in non-small cell lung cancer: implications for consistent nomenclature in precision medicine

Epidermal growth factor receptor (EGFR) exon 20 insertion mutations (E20ins) are the third most frequent mutations observed in non-small cell lung cancer, accounting for approximately 1–10% of all EGFRmutations. In the era of precision medicine and targeted therapies, consistent naming of genetic alterations is crucial to avoid confusion and errors. However, the annotation of EGFRE20ins mutations has been inconsistent, leading to confusion in the scientific literature and product documentation. In this study, our primary objective was to investigate the usage of different annotation related to EGFRE20ins in independent studies. Additionally, we assessed the distribution of EGFRE20ins mutations and estimated the detection coverage expected from each available EGFRE20ins detection assay. A total of 1,418 EGFR E20ins mutations were collected from six studies (FoundationInsights, Geneseeq Technology Inc, mobocertinib phase I/II trial, poziotinib phase II trial, sunvozertinib phase I trial, and Samsung Medical Center) and reorganised according to Human Genome Variation Society (HGVS) nomenclature. Our analysis revealed that the majority of EGFRE20ins mutations requiring correction were ‘insertion’ or ‘deletion-insertion’, which should be appropriately designated as ‘duplication’. Additionally, duplicated variants were reported using different annotations in each study, and furthermore, even identical variant sequences were annotated differently within the same study. In all six studies, p.A767_V769dup and p.S768_D770dup were the most frequently observed EGFRE20ins. The Oncomine Dx Target Test showed the highest patient coverage at 77.2%, followed by the Droplex EGFR Mutation Test v2 with a patient coverage of 70.5% for EGFRE20ins patients. To ensure comprehensive coverage in real-world settings, it is essential to standardise the annotations for each variant, for example using the HGVS nomenclature. The accurate classification and analysis of drug responsiveness in EGFRE20ins necessitate consideration of the nomenclature, particularly with respect to the locations where the actual mutations occur.