Resolving Resistance to Osimertinib Therapy With Afatinib in an NSCLC Patient With EGFR L718Q Mutation

Osimertinib, a third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI), has demonstrated significant efficacy against tumors with both EGFR TKI-sensitizing and EGFR T790M–resistant mutations. However, the disease of some patients eventually develops resistance with EGFR C797S mutation, which is the most common type of EGFR-resistant mutation. Previous studies showed that EGFR L718Q mutations that emerged concurrently with or without T790M mutations accounted for almost 10% of all cases after osimertinib resistance.