Asymptomatic Brain Metastasis in Non-small Cell Lung Cancer (NSCLC)

Inclusion Criteria: * Histologically confirmed non-small cell lung cancer with synchronous brain metastases (diagnosis of brain lesion before or within 2 months from diagnosis of the primary site tumor) * One to 4 intraparenchymal brain metastases by contrast-enhanced MRI, meeting the following criteria: 1. Well circumscribed tumor(s) with brain edema Grade 0-1 2. Maximum diameter ≤ 3.0 cm * No prior complete resection of all known brain metastases or RT ④ No leptomeningeal metastases by MRI or cerebrospinal fluid evaluation * 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: * severe co-morbid illness and/or active infections ② pregnant or lactating women * RTOG neurologic function status of 1\~4 ④ Uncontrollable extracranial metastases