Patients with stage III non-small-cell lung cancer initially evaluated as unresectable are selected for the program, who are remained unresectable after 2-4 cycles of conversion chemotherapy combined with immune checkpoint inhibitors. Investigators will stratify the treatment according to different performance status scores and radiotherapy plan bi-lung receptor volume to evaluate the safety and efficacy of immunotherapy followed by combined radiotherapy.

This is a prospective, real-world cohort study, which aimed to evaluate the safety and efficacy of immunotherapy followed by combined radiotherapy. Participants will be selected and entered into three different cohorts according to different performance status(PS) scores and radiotherapy schedules based on the amount of bilateral lungs treated. Cohort A: PS=0-1 and bilateral lung V20≤20%, mean lung dose(MLD)≤11 gray(Gy), radiotherapy and immunotherapy, followed by immunotherapy for up to 1 year; Cohort B: PS=0-1 and 20%\

Inclusion Criteria:

1. Histologically or cytologically confirmed non-small cell lung cancer
2. Presence of at least one measurable lesion according to RECIST 1.1 criteria
3. Classified as American Joint Committee on Cancer staging system, eighth edition (AJCC-8) Stage III, initially evaluated as unresectable and reevaluated as unresectable after 2-4 cycles of induction chemotherapy combined with immunotherapy
4. Age 18-75
5. Eastern Cooperative Oncology Group (ECOG) physical state score of 0-2
6. Patients with the pathologic type of adenocarcinoma should be negative for driver genes (EGFR, anaplastic lymphoma kinase, ROS1)
7. Serum hemoglobin ≥ 90 g/L, platelets ≥ 90 × 109/L, absolute neutrophil count ≥ 1.2 × 109/L
8. Serum creatinine ≤ 1.25 times upper limit of normal(ULN) or creatinine clearance ≥ 60 mL/min
9. Serum bilirubin ≤ 1.5 times ULN, (AST) and alanine aminotransferase aspartate aminotransferase (ALT) ≤ 2.5 times ULN, alkaline phosphatase ≤ 5 times ULN
10. Forced expiratory volume in one second (FEV1)>0.8 liter
11. Normal coagulation function (Prothrombin time prolonged by no more than 3s and activated partial thromboplastin time prolonged by no more than 10s)
12. Patients signed a formal informed consent form to indicate that they understood that the study complied with the hospital's policies and ethical requirements

Exclusion Criteria:

1. The pathologic type is lung carcinoid or small cell lung cancer
2. Patients with any distant metastases
3. Grade 2 or higher unresolved toxic effects after conversion therapy (according to the Common Terminology Criteria for Adverse Events CTCAE)
4. A recent efficacy rating of PD after conversion therapy
5. Radiotherapy plan for normal lung tissue V20 > 30%, or average lung dose MLD > 17 Gy
6. Active or previous autoimmune disease (within the past 2 years) or history of primary immunodeficiency
7. Patients with any other previous or current malignancy, except non-melanoma skin or cervical cancer in situ
8. Any other disease or condition suggesting a contraindication to radiotherapy (e.g., active infection, within 6 months of myocardial infarction, symptomatic cardiac disease including unstable angina pectoris, congestive heart failure, or uncontrolled arrhythmias, immunosuppressive therapy)
9. Pregnant or nursing women
10. Women and men who are at risk of becoming pregnant but are unwilling to use adequate contraception
11. Evidence of hereditary bleeding disorders or coagulation disorders.