Frequency, underdiagnosis, and heterogeneity of epidermal growth factor receptor exon 20 insertion mutations using real‐world genomic datasets

Abstract

Epidermal growth factor receptor (EGFR) exon 20 insertion mutations (ex20ins) account for ≤ 12% of all EGFR-mutant nonsmall cell lung cancers. We analysed real-world datasets to determine the frequency of ex20ins variants, and the ability of polymerase chain reaction (PCR) and nextgeneration sequencing (NGS) to identify them. Three real-world United States NGS databases were used: GENIE, FoundationInsights, and GuardantINFORM. Mutation profiles consistent with in-frame EGFR ex20ins were summarized. GENIE, FoundationInsights, and Guardant-INFORM datasets identified 180, 627, and 627 patients with EGFR ex20ins respectively. The most frequent insertion region of exon 20 was the near loop (~70%), followed by the far loop (~30%) and the helical (~3-6%) regions. GENIE, FoundationInsights, and GuardantINFORM datasets identified 41, 102, and 96 unique variants respectively. An analysis of variants projected that ~50% of EGFR ex20ins identified by NGS would have been missed by PCR-based assays. Given the breadth of EGFR ex20ins identified in the real-world US datasets, the ability of PCR to identify these mutations is limited. NGS platforms are more appropriate to identify patients likely to benefit from EGFR ex20ins-targeted therapies.

Current status and breakthroughs in treating advanced non-small cell lung cancer with EGFR exon 20 insertion mutations

“…The modified interaction typically leads to a greater distance between the end of the beta3 strand and the beginning of the N-terminus ( Figure 1 ), pulling the C-helix towards the C-in position, making it sensitive to TKIs ( 22 , 27 , 28 ). Currently, more than 100 activating mutations of EGFR ex20ins mutations have been identified worldwide, mainly stimulated by conformational activation of the EGFR pathway ( 22 , 29 , 30 ), with approximately 85 known EGFR ex20ins mutant isoforms in China ( 31 ). Common mutant isoforms include S768_D770dup, H773_V774dup, A763_Y764insFQEA, D770_N771insG, D770delinsGY, N771_H773dup, P772_H773dup, H773_V774insAH, and H773dup ( 32 ).…”

Epidemiological characteristics and therapeutic advances of EGFR exon 20 insertion mutations in non‐small cell lung cancer

“…Studies have indicated that PCR-based assays can only identify about 11.8%-58.9% of EGFRex20ins mutations detected by NGS, indicating that more than 40% of such patients may be missed by PCR-based assays. 20,22,26 Given the better depth and breadth of NGS detection, it has been widely used in clinical practice in recent years, perhaps accounting for the increased detection frequency of EGFRex20ins mutations in recent years. 23 It is worth mentioning that collecting tissue samples acceptable for molecular testing is difficult in a considerable proportion of advanced NSCLC patients (approximately 30%).…”

“…7,19 Based on the insertion site and the amino acid sequence, this mutation can be further categorized into three categories: insertions in the αC helix, insertions occurring in the C-terminal near-loop (767-772) of the αC helix (Ex20ins-NL), and the insertions in the far-loop (773-775, Ex20ins-FL). 20 Different insertion sites have been reported to be associated with varying sensitivity to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs). 19,21 Proportionally, the major insertion sites are reported to be at AA769, AA770, and AA773, with over 90% of insertions occurring within the loop structure, with the Ex20ins-NL being the most frequent (approximately 70%).…”

“…Structurally, exon 20 of EGFR spans AA 762–823, encoding the tyrosine kinase domain, and contains the regulatory αC helix (AA762‐766) and adjacent loop (AA767‐774) 7,19 . Based on the insertion site and the amino acid sequence, this mutation can be further categorized into three categories: insertions in the αC helix, insertions occurring in the C‐terminal near‐loop (767–772) of the αC helix (Ex20ins‐NL), and the insertions in the far‐loop (773–775, Ex20ins‐FL) 20 . Different insertion sites have been reported to be associated with varying sensitivity to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR‐TKIs) 19,21 .…”

“…Hence, NGS‐based assays are preferable. Studies have indicated that PCR‐based assays can only identify about 11.8%–58.9% of EGFRex20ins mutations detected by NGS, indicating that more than 40% of such patients may be missed by PCR‐based assays 20,22,26 . Given the better depth and breadth of NGS detection, it has been widely used in clinical practice in recent years, perhaps accounting for the increased detection frequency of EGFRex20ins mutations in recent years 23 …”