The dynamic monitoring of circulating tumor DNA aims to evaluate the response and progression-free survival of short-course chemotherapy (2 cycles) combined with immunotherapy in patients with locally advanced unresectable or metastatic non-small cell lung cancer.

For patients with locally advanced unresectable or metastatic non-small cell lung cancers, 4-6 cycles of chemotherapy plus immunotherapy with immune maintenance therapy is currently the standard treatment. Short-course chemotherapy (2 cycles) combined with immunotherapy has been proved effective in some patients. Recently, circulating tumor DNA (ctDNA) has been detected in the cell-free component of peripheral blood samples in advanced non-small cell lung cancers and many other solid tumors. To identify the patients who can benefit from the short-course chemotherapy (2 cycles) combined with immunotherapy, dynamic monitoring of ctDNA in both 4-6 cycles and 2 cycles chemotherapy patients could be a promising alternative test.

Inclusion Criteria:

• (1)Histologically confirmed non-small cell lung cancer; (2)Locally advanced unresectable or metastatic disease; (3)Male or female aged over 18 years and under 80 years; (4)Subjects must not have received any immunotherapy for advanced lung cancer, and have an estimated life expectancy of more than 12 weeks (5)Eastern Cooperative Oncology Group (ECOG) score as 0 ~ 1; (6)No EGFR mutation, ALK or ROS1 rearrangement; (7)Adequate tumor tissue for PD-L1 testing; (8)With at least one measurable lesion confirmed by the investigator according to Response Evaluation Criteria in Solid Tumors (RECIST) (version 1.1)； (9)The subjects must sign the informed consent, indicating that they understand the purpose of the study, understand the necessary procedures of the study, and are willing to participate in the study.

Exclusion Criteria:

• (1)Serious immune-related adverse events occurred; (2)Participation in other clinical study; (3)With the history of autoimmune disease or immunodeficiency disease; (4)History of another primary malignancy within 5 years; (5)Without complete clinical information; (6)Pregnant or lactating women; (7)Other conditions in which the investigator believes that the patient should not participate in this trial.

Male or female aged over 18 years and under 80 years with locally advanced unresectable or metastatic non-small cell lung cancer, and no prior immunotherapy.