Abstract
With the rapid development of precision medicine, next generation sequencing (NGS) has provided the ability to decode tumors at the DNA level. In treatment of patients with non-small cell lung cancer (NSCLC), it is of great importance to identify epidermal growth factor receptor (EGFR) mutations and drug resistance mechanisms in the late stages. A Chinese Han male patient (64 years old) who was initially diagnosed with EGFR-19-deletion-positive advanced NSCLC had a satisfactory clinical response after treatment with erlotinib. Subsequently, the disease progressed and NGS in plasma-derived circulating tumor DNA (ctDNA) revealed T790M mutation. The patient was then treated with osimertinib. In addition, NGS in ctDNA was performed again after the disease progressed, suggesting that MET was amplified, and then the patient was alternatively treated with combination therapy of crizotinib and erlotinib. The disease progressed for the third time, and treatment with osimertinib was undertaken again according to the T790M testing results. Dynamic monitoring of ctDNA was found to be helpful in selecting the appropriate treatment methods and prolonging the survival time of the patient.