Durable response to osimertinib in an advanced lung adenocarcinoma patient with an uncommon EGFR T854A mutation: A case report.

Abstract

Epidermal growth factor receptor (EGFR) T854A mutation in exon 21 is an uncommon EGFR mutation in patients with non-small cell lung cancer (NSCLC). It is a secondary EGFR mutation after first- and second-generation EGFR tyrosine kinase inhibitors (TKIs). All EGFR T854A mutations were co-occurred with EGFR L858R mutation in cis. There is still no clear evidence to guide the therapeutic options for patients with both EGFR T790M and T854A mutations. A 60-year-old Chinese woman with no smoking history presented with a maximum diameter of 32.9 mm mass located in the right lower lung lobe. The patient was diagnosed with stage IVA lung adenocarcinoma with an exceptionally uncommon EGFR T854A mutation in exon 21 was detected concomitantly with EGFR T790M in blood by next-generation sequencing (NGS). The patient was initially treated with first-line afatinib. After disease progression, osimertinib was administered. Our patient exhibited a partial response (PR) to osimertinib with progression-free survival of nearly 8 months. Our study indicates that patients with NSCLC who are positive for uncommon EGFR T854A and T790M mutations might benefit from treatment with osimertinib.