Efficacy of osimertinib in a patient with non-small cell lung cancer harboring epithelial growth factor receptor exon 19 deletion/T790M mutation, with poor performance status

Osimertinib, a third-generation epithelial growth factor receptor (EGFR) tyrosine kinase inhibitor, has been demonstrated to be effective for treating patients with T790M-positive advanced non-small cell lung cancer (NSCLC) with a relatively good performance status (grade 0-1). Reports of therapeutic response to osimertinib in advanced NSCLC patients with poor performance status are infrequent. The present case report discusses a patient with advanced lung adenocarcinoma harboring EGFR exon 19 deletion and T790M mutation with central nervous system involvement and poor performance status. The patient had a past history of partial lung resection due to lung adenocarcinoma, positive genetic test for EGFR exon 19 deletion in post-surgical tumor specimens, and therapy with erlotinib and onartuzumab for the appearance of a lung metastatic tumor during the post-surgical follow-up. The combined therapy was continued until the discovery of metastatic tumors in bones and the central nervous system. The Cobas test performed using tissue from bone metastatic tumor was positive for exon 19 deletion and for T790M mutation. The patient was treated with osimertinib and adverse effects or hematological toxicity were not observed. Performance status of the patient improved from grade 4 to 2. Subsequent studies revealed remission of bone metastasis and reduced central nervous system lesions. This report provides evidence on the safety and efficacy of osimertinib for treating NSCLC patients with progressive disease, central nervous system lesion and poor performance status.