A Phase Ib Study of TQB2450 Combined With Anlotinib in Patients With Limited Stage Small Cell Lung Cancer After First-line Radiotherapy and Chemotherapy

Inclusion Criteria: * The subject voluntarily joins the study, signs the informed consent form, and has good compliance; * Age: 18\~75 years old (when signing the informed consent form); ECOG PS score: 0-1 points; Expected survival beyond 6 months; body weight\> 40 kg; * Patients with pathologically confirmed limited-stage small cell lung cancer (according to the Veterans Administration Lung Study Group (VALG stage); * Through the neck, chest, abdomen, pelvic enhanced CT and brain plain scan + enhanced MRI examination with diagnostic quality, there is no evidence of metastatic disease (PET-CT examination is recommended before starting radiotherapy and chemotherapy, if not performed before radiotherapy and chemotherapy PET-CT examination, bone scan examination should be performed; PET-CT examination must be performed during the screening period after chemoradiotherapy to exclude metastasis); * It is expected that no tumor resection will be required during the study (patients who are not suitable for surgery or those who are unwilling to undergo surgery are acceptable); * Radiotherapy technology adopts three-dimensional conformal radiotherapy, conformal intensity-modulated radiotherapy, tomographic radiation therapy and other precision radiotherapy technologies; * Patients must achieve CR, PR or SD after receiving radical platinum-based CRT and cannot develop disease progression; * Patients with at least one measurable lesion confirmed according to RECIST 1.1 criteria prior to chemoradiotherapy; Exclusion Criteria: * Complex small cell lung cancer confirmed by histopathology or cytopathology; * Subjects with known central nervous system metastasis and/or cancerous meningitis; * Malignant pleural effusion and pericardial effusion; * Imaging shows that the tumor has invaded important blood vessels, or the researcher has determined that the tumor is highly likely to invade important blood vessels and cause fatal massive bleeding during subsequent studies; * Within 2 weeks before the start of the study treatment, he has received the treatment of traditional Chinese patent medicines and simple preparations with anti-tumor indications specified in the NMPA approved drug manual; * Patients who have received immunomodulatory drugs within 30 days before starting treatment; * Previously received anti PD-1, anti PD-L1, or anti PD-L2 drugs or medication targeting another stimulating or co inhibitory T cell receptor; * Previous use of antivascular survival drugs（ bevacizumab, arotinib, apatinib ,ect);