Chemotherapy With or Without Radiosurgery for Asymptomatic Oligo Brain Metastasis

Inclusion Criteria: 1. Histologically confirmed non-small cell lung cancer with synchronous brain metastases 2. One to 4 intraparenchymal brain metastases by contrast-enhanced MRI, meeting the following criteria: * Well circumscribed tumor(s) with brain edema Grade 0-1 * Maximum diameter ≤ 3.0 cm 3. No prior surgical treatment or RT for brain metastases 4. No leptomeningeal metastases by MRI or cerebrospinal fluid evaluation 5. Patients without any symptoms or signs from brain metastases (RTOG neurologic functions status of 0) 6. Age, 18 and over 7. ECOG performance status 0-1 8. Written informed consent Exclusion Criteria: 1. severe co-morbid illness and/or active infections 2. pregnant or lactating women 3. RTOG neurologic function status of 1\~4 4. Uncontrollable extracranial metastases