Heterogeneous Response to First-Generation Tyrosine Kinase Inhibitors in Non-Small-Cell Lung Cancers with Different EGFR Exon 19 Mutations.

Deletion location and type variants (with or without an insertion and/or a substitution) might affect first-generation TKI efficacy, and different EGFR exon 19dels should be considered when making decisions on which EGFR TKI should be used.