TRT for ES-SCLC After First Line Treatment With Immune Checkpoint Inhibitors

Inclusion Criteria: * Age at least 18 years. * ECOG PS 0-1. * Histological or cytological syndrome of small cell lung cancer, imaging evaluation staging is extensive * Life expectancy \>= 3 months. * Patients are non-progressed after 4 dosed of immunotherapy plus platinum based chemotherapy, with residual thoracic lesions * Palliative radiotherapy were allowed except for TRT, the interval \> 4 weeks * Adequate organ function prior to enrollment: * Adequate bone marrow function: white blood cell (WBC) count ≥ 3.0 \* 10 \^ 9/L or neutrophil count ≥ 1.5 \* 10 \^ 9/L, platelet count ≥ 100 \* 10 \^ 9/L and hemoglobin ≥90g/L,; * Adequate hepatic function: total bilirubin, urea nitrogen and serum creatinine≤ 1.5 x upper limit of normal (ULN). Aspartate aminotransferase (AST) and Alanine aminotransferase (ALT) ≤2.0 ULN; * Sufficient heart and lung function, EF\>55%FEV1\>50% * Ability to understand and willingness to provide the informed consent. * Women of childbearing age and men must agree to use effective contraception during the trial. Exclusion Criteria: * History of another malignancy or concurrent malignancy; * Mixed small cell with non-small cell lung cancer histology; * History of thoracic radiotherapy; * Malignant pleural or ascites; * Patients with leptomeningeal metastasis or uncontrolled brain; * Severe autoimmune disease: inflammatory bowel disease (including Crohn's disease and ulcerative colitis), rheumatoid arthritis, scleroderma, systemic lupus erythematosus, Wegener's granulomatosis and related vasculitides. * Symptomatic interstitial lung disease or clinically active infectious/non-infectious pneumonitis. * Active infection, congestive heart failure, or any evidence of myocardial infarction, unstable angina pectoris or cardiac arrhythmia within 6 months prior to enrollment. * The patient is pregnant (confirmed by serum b-HCG if applicable) or is breastfeeding. * Mental disorders, drug abuse, and social condition that may negatively impact compliance in the investigator's opinion.