This study aims to explore the safety and efficacy of eliminating the planning target volume (PTV) margins based on MRI-guided adaptive stereotactic radiotherapy for non-small cell lung cancer (NSCLC) patients with brain metastasis.

This study aims to explore the safety and efficacy of eliminating the planning target volume (PTV) margins based on MRI-guided adaptive stereotactic radiotherapy for NSCLC patients with brain metastasis. In this study, patients will be randomly assigned in a 1:1 ratio to the study group or the control group. Patients in the study group will receive MRI-guided adaptive stereotactic radiotherapy (SRT) (without PTV expansion margin), while patients in the control group will receive CT-guided conventional standard SRT (with PTV expansion margin). After the completion of treatment, patients will be followed up regularly to assess safety and efficacy.

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
• 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