ctDNA Analysis to Monitor the Risk of Progression After First-line Immunotherapy in Patients With Advanced NSCLC

Inclusion Criteria: * Age ≥ 18 years old * Advanced non-small cell lung cancer (stage IIIB-IV), pathological types limited to squamous cell carcinoma or non-squamous cell carcinoma, driver gene mutations (EGFR/ALK/ROS1) were negative * General condition: ECOG score 0 or 1 * First-line monotherapy or combination immunotherapy * The long-term benefit of immunotherapy was defined as PFS=12months * Tumor tissue samples can be obtained at the time of enrollment, and at least 5 \~ 10 sections can be generated, and the pathological report indicates that the overall tumor content is not less than 10% or NGS testing with a fixed-panel is available; or no tumor tissue is available. * At least one measurable lesion (except patients with CR after first-line treatment) can be evaluated according to RECIST1.1 standard. * Have self-awareness, be able to understand the research scheme and voluntarily participate in the study, and can sign the informed consent form * Have good compliance, be able to cooperate with the collection of specimens from each node and provide corresponding clinical information. Exclusion Criteria: * Serious primary diseases of the heart, liver and kidney * Other malignant tumors within 3 years prior to diagnosis of NSCLC * Women in pregnancy and lactation * The active stage of human immunodeficiency virus (HIV) infection * Patients with active systemic infection, pneumonia, tuberculosis, pericarditis * Patients who cannot understand the content of the experiment and cannot cooperate and refuse to sign informed consent.