A comprehensive overview of the heterogeneity of EGFR exon 20 variants in NSCLC and (pre)clinical activity to currently available treatments.

Activating EGFR mutations are commonly observed in non-small cell lung cancer (NSCLC). About 4-10 % of all activating epidermal growth factor receptor (EGFR) mutations are heterogenous in-frame deletion and/or insertion mutations clustering within exon 20 (EGFRex20+). NSCLC patients with EGFRex20+ mutations are treated as a single disease entity, irrespective of the type and location of the mutation. Here, we provide a comprehensive assessment of the literature reporting both in vitro and clinical drug sensitivity across different EGFRex20+ mutations. The activating A763_Y764insFQEA mutation has a better tumor response in comparison with mutations in the near- and far regions directly following the C-helix and should therefore be treated differently. For other EGFRex20+ mutations marked differences in treatment responses have been reported indicating the need for a classification beyond the exon-based classification. A further classification can be achieved using a structure-function modeling approach and experimental data using patient-derived cell lines. The detailed overview of TKI responses for each EGFRex20+ mutation can assist treating physicians to select the most optimal drug for individual NSCLC patients.