Sintilimab Combined With Anlotinib as Second or Further-line Therapy for ED-SCLC

Inclusion Criteria: Patients must meet all of the following criteria to be enrolled: * Histologically or cytologically confirmed ED-SCLC according to the VALG staging system, and not suitable for local treatment. * Progressed after at least one line of platinum-containing chemotherapy. * ≥1 measurable lesions based on Response Evaluation Criteria In Solid Tumors version 1.1 (RECIST v1.1). * Previous radiotherapy was allowed, but the radiotherapy area must be \<25% of the bone marrow area (Cristy and Eckerman 1987) and no total pelvic or chest irradiation was used; the previous radiotherapy must have been completed for at least 4 weeks before the start of study drugs treatment, and the acute toxicity must have been restored; radiotherapy of local lesions cannot be included in measurable lesions unless significant progression is noted after radiotherapy. * Prior surgery was allowed, provided that the treatment was completed at least 4 weeks before the start of study drugs treatment, and the acute toxicity must have been restored. * ≥18 years old. * Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0-2. * Life expectancy \> 12 weeks. * Adequate bone marrow, hepatic and renal function. * Systolic blood pressure ≤160mmHg and diastolic pressure ≤90mmHg within 7 days before enrollment. * Patients must sign study specific informed consent before registration. * Female patients should be surgically sterilized, postmenopausal, or consent to use a medically approved contraceptive method (such as an IUD, contraceptive pill, or condom) during the study treatment period and for 6 months after the end of the study treatment period; Serum or urine pregnancy tests must be negative within 7 days prior to study enrollment and must be non-lactating; Male patients should be surgically sterilized or who have consented to use a medically approved form of contraception during the study treatment period and for 6 months after the end of the study treatment period. Exclusion Criteria: Any of the following conditions should not be included in this study: * Patients with brain metastasis. Patients suspected of having brain metastases should be examined by brain CT or MRI before enrollment; Patients with a history of brain metastases must have completed treatment and no longer need corticosteroids; For asymptomatic patients, the investigator will determine whether to enroll. * Patients with meningeal metastasis. * Prior treatment with PD-1 inhibitor, PD-L1 inhibitor, CTLA4 inhibitor, or anti-angiogenic treatment. * Accept any other anti-tumor treatment simultaneously. * Diagnosed with active autoimmune diseases (congenital or acquired, patients with completely relieved or childhood vitiligo can be enrolled; patients with hypothyroidism and only need hormone replacement therapy can be rerolled; Patients with type 1 diabetes can also be enrolled). * Diagnosed with interstitial pneumonia. * Patients with hemorrhage tendency including acute hemorrhage of digestive tract, continuous hemorrhage disease or coagulation function disorder disease. * Patients are using warfarin, heparin or aspirin (\>325 mg/day) or NSAIDS to inhibit platelet function within 10 days prior to enrollment, or receiving dipyridamole, ticlopidine, clopidogrel or cilostazol treatment. * Patients with accompanying diseases that seriously endanger the safety of the patient or affect the patient's completion of the study. * Pregnant or lactating female. * Prior other malignant diseases, except for cervical carcinoma in situ, papillary thyroid carcinoma, or non-melanoma skin cancer. * Allergy to any component of the study drugs.