This study is a multicenter, randomized, prospective Phase III study to evaluate the efficacy and safety of anlotinib plus whole-brain radiotherapy (WBRT) compared with WBRT alone in small cell lung cancer (SCLC) patients with brain metastases. Additionally, by investigating the association between changes in circulating tumor cell (CTC) levels in peripheral blood and treatment response to the combination of targeted therapy and radiotherapy, we aim to identify a patient subgroup most likely to benefit from this regimen, as well as potential biomarkers predictive of treatment efficacy.

Inclusion Criteria:

• Small cell lung cancer confirmed by pathology, with brain metastases diagnosed either at initial presentation or during treatment, and measurable disease according to RECIST criteria.
• The expected survival time is more than 3 months.
• Intracranial metastases ≤10.
• Adequate organ and bone marrow function.
• Women of childbearing potential must agree to use effective contraception during the study and for 6 months after its completion.

Exclusion Criteria:

• Patients who have used antiangiogenic drugs within the previous 1 month.
• Non-small cell lung cancer (including combined small cell carcinoma).
• Small cell lung cancer with hilar invasion or hemoptysis.
• Patients with intracranial acute, subacute cerebral infarction, intracranial lesions acute, subacute hemorrhage.
• An unresolved acute toxic reaction period higher than grade 2 of CTC-AE(4.0) due to any prior treatment.
• Advanced patients with severe symptoms, tumors that have spread to the internal organs, and a short-term risk of life-threatening complications.
• Patients with life-threatening conditions of other severe and/or uncontrolled diseases.
• History of prior brain radiotherapy.