Treatment Response Adapted Hybrid Radiotherapy in Metastatic Non-small Cell Lung Cancer Receiving First-line Immunotherapy

Inclusion Criteria:

* ECOG functional status score was 0-1.
* Histologically confirmed stage IV primary NSCLC;
* Genetic testing showed that the common driver genes including EGFR, ALK and ROS-1 were negative;
* Patients with brain metastases were eligible if they were neurologically asymptomatic and had stable disease without receiving systemic glucocorticoids;
* According to the investigator's judgment, the patient does not need to receive palliative radiotherapy for any site at present;
* Male/female of childbearing age agreed to use contraception (surgical ligation or oral contraceptive/intrauterine device plus condom) during the trial;
* Life expectancy ≥3 months;
* One week before enrollment, the organ function level met the following criteria:

  ① Bone marrow function: hemoglobin ≥80g/L, white blood cell count ≥4.0\*10\^9/L or neutrophil count ≥1.5\*10\^9/L, platelet count ≥100\*10\^9/L;

  ② Liver: serum total bilirubin level ≤1.5 times upper limit of normal, direct bilirubin level must be ≤1.5 times upper limit of normal, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤2.5 times upper limit of normal;

  ③ Kidney: serum creatinine \< 1.5 times upper limit of normal or creatinine clearance ≥50ml/min, urea nitrogen ≤200mg/L; Serum albumin ≥30g/L;
* Patients must be able to understand and voluntarily sign the informed consent form.

Exclusion Criteria:

* The patient had severe autoimmune diseases: active inflammatory bowel disease (including Crohn's disease, ulcerative colitis), rheumatoid arthritis, scleroderma, systemic lupus erythematosus, autoimmune vasculitis (such as Wegener's granulomatosis), etc.
* Symptomatic interstitial lung disease or active infectious/non-infectious pneumonia;
* Patients with risk factors for intestinal perforation: active diverticulitis, intra-abdominal abscess, gastrointestinal (GI) obstruction, abdominal cancer, or other known risk factors for intestinal perforation;
* History of other malignant tumors;
* Patients with active infection, heart failure, myocardial infarction, unstable angina or unstable arrhythmia within the past 6 months;
* Medical examination or clinical findings, or other uncontrollable conditions that the investigator considers may interfere with the results or increase the patient's risk of treatment complications;
* Patients who were considered by the investigator to have lesions requiring palliative and subtractive radiotherapy;
* Mixed with small cell lung cancer components;
* Lactating or pregnant women;
* Congenital or acquired immunodeficiency diseases including human immunodeficiency virus (HIV), organ transplantation or allogeneic stem cell transplantation;
* Known HBV, HCV, active pulmonary tuberculosis infection;
* Patients had received a cancer vaccine or received another vaccine within 4 weeks before starting treatment (note: injectable seasonal influenza vaccine is usually inactivated, so vaccination is allowed, while intranasal vaccine is usually live attenuated, so it is not allowed);
* Patients with concurrent use of other immune agents, chemotherapy drugs, drugs in other clinical studies, and long-term use of cortisol were excluded.
* Patients with mental disorders, substance abuse, or social problems that affect adherence were excluded from the study after physician review;
* Patients who are allergic to or contraindicated to PD-1 monoclonal antibody or chemotherapy drugs.