Triple administration of osimertinib followed by chemotherapy for advanced lung adenocarcinoma: A case report

BACKGROUND Osimertinib is the recommended first-line treatment for adult patients with epidermal growth factor receptor (EGFR) mutation positive advanced or metastatic non-small cell lung cancer (NSCLC). However, primary or acquired resistance to EGFR-tyrosine kinase inhibitors (EGFR-TKIs) seems inevitable, and when drug-resistance occurs during treatment with osimertinib, the standard of care is to discontinue the TKI. CASE SUMMARY A 57-year-old female patient with lung adenocarcinoma presented with an irritating cough accompanied by chest distress of one month duration. An enhanced head magnetic resonance imaging scan showed brain metastases. An EGFR mutation (exon 21 L858R) was detected in pleural fluid. The patient was treated with oral osimertinib (80 mg once daily) from January 2018 but developed progressive disease on December 2018. She was then successfully treated with re-challenge and tri-challenge with osimertinib (80 mg once daily) by resensitization chemotherapy twice after the occurrence of drug-resistance to osimertinib, and to date has survived for 31 mo. CONCLUSION This case may provide some selective therapeutic options for NSCLC patients with acquired drug-resistance who were previously controlled on osimertinib treatment.