Different efficacy of osimertinib in pre-TKI treated NSCLC patients with brain metastases harboring EGFR exon 19del and L858R mutant.

e21667Background: Previous studies suggested that the efficacy of osimertinib was better in patients with epidermal growth factor receptor (EGFR) exon 19 deletion (ex19del) than exon 21 Leu858Arg (...