Exploration of Whole-Brain Radiotherapy Combined With PD-1 Inhibitors on Brain Injury

The study aims to enroll the small cell lung cancer(SCLC) who meet the indications for prophylactic cranial irradiation (PCI): patients with limited-stage SCLC who have achieved complete or partial remission after first-line treatment, or patients with extensive-stage SCLC whose tumors are effectively controlled after systemic therapy with no definitive evidence of brain metastases. Additional inclusion criteria are expected survival≥6 months, completion of at least 12 months of follow-up, and signed informed consent obtained before enrollment after explaining the study objectives and methods.The observation group consists of patients with extensive-stage SCLC receiving first-line chemotherapy combined with concurrent immunotherapy. After two cycles, patients with a confirmed response (CR, PR, or SD) undergo PCI. The control group consists of patients with limited-stage SCLC receiving standard concurrent chemoradiotherapy (systemic therapy plus thoracic radiotherapy). After two cycles of systemic therapy, those with a confirmed response undergo PCI.Starting from the completion of PCI, contrast-enhanced MRI of the brain (plain scan, contrast-enhanced scan, and DWI) and contrast-enhanced CT of the chest and whole abdomen are performed every three months. Treatment-related toxicity is evaluated using CTCAE v5.0. Cognitive function is assessed every three months using the Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA). Venous blood samples are collected one day before radiotherapy and every three months thereafter to measure white blood cells, neutrophils, lymphocytes, platelets, hemoglobin, liver function, renal function, electrolytes, and coagulation function; stool and urine tests are also performed. The data are analyzed to determine whether whole-brain radiotherapy combined with immunotherapy exacerbates neurological impairment.