Third-generation EGFR-TKI Treatment in Metastatic EGFR-mutant NSCLC

Inclusion Criteria: * Pathologically confirmed non-small cell lung cancer; * clinical stage IV (AJCC, 8th edition, 2017); * EGFR sensitizing mutations (L858R or 19del); * age≥18 years old; * KPS score≥70; * complete systemic imaging (including brain MRI) before third-generation EGFR-TKI treatment; * received standard third-generation EGFR-TKI therapy (monotherapy or combined with brain radiotherapy); * willing to cooperate with the follow-up after third-generation EGFR-TKI treatment; * informed consent of the patient. Exclusion Criteria: * Multiple primary or metastatic tumors (except early skin cancer, cervical carcinoma in situ that has been treated radically, with no recurrence or progression for more than 5 years); * Pregnant or lactating women who, as judged by the investigator, were not candidates for brain MRI; * Uncontrolled epilepsy, central nervous system disease, or history of mental disorders, judged by the researcher to potentially interfere with the signing of the informed consent form or affect patient compliance.; * patients without EGFR sensitive mutations or with unknown EGFR mutation status. Withdrawal criteria * The investigators considered that the patients had poor adherence to the study protocol. * The patient withdrew informed consent and asked to withdraw. * There was any safety reason (adverse event) considered by the investigator; * Due to other underlying diseases, side effects, economic factors, and other reasons, patients did not receive regular doses of third-generation EGFR-TKI (continuous withdrawal time more than 1 week, cumulative withdrawal time more than 2 weeks, etc.). * The patient was not followed up according to the protocol. * Other circumstances in which withdrawal from the study was deemed necessary by the investigator.