The goal of this observational study is to explore the feasibility of stereotactic radiotherapy (SRT) as consolidation therapy for patients with advanced non-small-cell lung cancer who were treated with third-generation epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI). The investigators plan to explore the time to achieve the best response after EGFR-TKI treatment, the characteristics of the distribution of lesions when the best response is achieved, the feasibility of SRT when the best response is achieved, and the phenotype of disease progression after EGFR-TKI resistance.

In summary, this study will provide critical information for exploring the feasibility and optimal design of SRT as consolidation therapy for advanced NSCLC patients treated with third-generation EGFR-TKI, which will further promote the optimization of comprehensive treatment for EGFR-mutant advanced 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.

Advanced EGFR-mutant NSCLC patients receiving third-generation EGFR-TKIs are enrolled