Tumor tissue samples will be obtained by biopsy.
Although some small sample studies have reported the possible resistance mechanisms of Osimertinib in the first-line treatment, it is still an urgent need to explore the whole gene profile in EGFRm advanced NSCLC patients post Osimertinib 1L treatment by paired tissue and plasma to guide subsequent treatment strategy. Thus, the gene profile post Osimertinib 1L treatment in tissue and plasma may help to guide the following treatment.~Participants will be required to provide paired tissue and whole blood after disease progression following 1L Osimertinib. 200 tissue samples and 200 whole blood samples will be used to detect gene alteration by NGS, respectively. 200 tissue samples will be used to detect pathological transformation by IHC.