Beneficial Effect of Osimertinib Readministration in Non-small-cell Lung Cancer Harboring an Epidermal Growth Factor Receptor (EGFR) Mutation with a History of Acquired Resistance to Osimertinib.

We herein report a case of the beneficial effect of osimertinib readministration in non-small-cell lung cancer (NSCLC) harboring an epidermal growth factor receptor (EGFR) mutation. A 69-year-old non-smoking woman was diagnosed with advanced NSCLC harboring an EGFR exon19 deletion and T790M. She was treated with osimertinib for two years but eventually acquired resistance. After 1.5 years of salvage chemotherapies, osimertinib was re-administered. She has been effectively and safely treated with osimertinib readministration for over 10 months. A prospective study is warranted to evaluate the efficacy and safety of osimertinib readministration in NSCLC with EGFR mutations.