MR-Linac Guided Adaptive FSRT for Brain Metastases From Non-small Cell Lung Cancer

Inclusion Criteria: * Aged 18-75 years * Histologically or cytologically confirmed non-small cell lung cancer * 1-10 metastases on contrast-enhanced MRI * Radiotherapy for extracranial lesions is permitted * Tyrosine kinase inhibitors (TKI) are permitted in patients with progression of intracranial metastases during previous TKI therapy * Patients have measurable or evaluable lesions based on the Response Evaluation Criteria in Solid Tumors (RECIST) criteria * Eastern Cooperative Oncology Group (ECOG) performance status 0-1 * Normal function of organs and bone marrow within 14 days: Total bilirubin 1.5 times or less the upper limits of normal (ULN); AST and ALT 1.5 times or less the ULN; absolute neutrophil count≥ 500 cells/mm3; creatinine clearance rate(CCR) ≥45 mL/min; Platelet count≥50,000 cells/mm3; international normalized ratio(INR) ≤1.5#Prothrombin Time (PT)≤ 1.5 × ULN * Informed-consent Exclusion Criteria: * Small cell carcinoma of lung * Intracranial metastases needed surgical decompression * Patients with contraindications for MRI * Previous radiotherapy or excision for intracranial metastases * The tumor has completely approached, encircled, or invaded the intravascular space of the great vessels (e.g., the pulmonary artery or the superior vena cava) * A cavity over 2cm in diameter of primary tumor or metastasis * Bleeding tendency or coagulation disorder * Hemoptysis (1/2 teaspoon blood/day) happened within 1 month * The use of full-dose anticoagulation within the past 1 month * Severe vascular disease occurred within 6 months * Gastrointestinal fistula, perforation or abdominal abscess occurred within 6 months * Hypertensive crisis, hypertensive encephalopathy, symptomatic heart failure (New York class II or above), active cerebrovascular disease or cardiovascular disease occurred within 6 months * Uncontrolled hypertension (systolic \> 150mmHg and/or diastolic \> 100mmHg) * Major surgery within 28 days or minor surgery or needle biopsy within 48 hours * Urine protein 3-4+, or 24h urine protein quantitative \>1g * Severe uncontrolled disease * Uncontrollable seizure or psychotic patients without self-control ability * Women in pregnancy, lactation period * Other not suitable conditions determined by the investigators