LAUSR

Introduction: EGFR exon 20 insertions (EGFRex20ins) comprise an uncommon subset of EGFR‐activating alterations relatively insensitive to first‐ and second‐generation EGFR tyrosine kinase inhibitors (TKIs). However, recent early clinical data suggests these patients may benefit from newer‐generation EGFR‐TKIs. Comprehensive genomic profiling (CGP) identifies a broad spectrum of EGFRex20ins and associated co‐occurring genomic alterations (GAs) present in NSCLC. Methods: Hybrid capture‐based CGP was performed prospectively on 14,483 clinically annotated consecutive NSCLC specimens to a mean coverage depth of greater than 650X for 236 or 315 cancer‐related genes. Results: Of 14,483 NSCLC cases, CGP identified 263 (1.8%) cases with EGFRex20ins, representing 12% (263 of 2251) of cases with EGFR mutations. Sixty‐four unique EGFRex20ins were identified, most commonly D770_N771>ASVDN (21%) and N771_P772>SVDNP (20%). EGFR amplification occurred in 22% (57 of 263). The most common co‐occurring GAs effected tumor protein p53 (TP53) (56%), cyclin dependent kinase inhibitor 2A (CDKN2A) (22%), cyclin dependent kinase inhibitor 2B (CDKN2B) (16%), NK2 homeobox 1 (NKX2‐1) (14%) and RB transcriptional corepressor 1 (RB1) (11%); co‐occurring GAs in other known lung cancer drivers were rare (5%). Average tumor mutational burden was low (mean 4.3, range 0 to 40.3 mutations/Mb). Clinical outcomes to first‐ and second‐generation EGFR TKIs were obtained for five patients and none responded. Conclusions: In the largest series of EGFRex20ins NSCLC, diverse EGFRex20ins were detected in 12% of EGFR‐mutant NSCLC, a higher frequency than previously reported in smaller single‐institution studies. Clinical outcomes showed lack of response to EGFR TKIs. Tumor mutational burden was low, consistent with non–smoking associated NSCLC. Comprehensive sequencing revealed increased proportion and wide variety of EGFRex20ins, representing a population of patients significant enough for focused efforts on effective interventions.