Efficacy of Gefitinib for Brain Metastasis of Non-Small Cell Lung Cancer

This is a non-randomized open-label uncontrolled phase II trial evaluating efficacy and toxicity of gefitinib in patients with asymptomatic advanced NSCLC who was benefitted by first line chemotherapy. Patients with stage IV NSCLC who have one or more asymptomatic brain metastasis who was benefitted by first line chemotherapy will receive oral gefitinib 250mg once daily until disease progression or unacceptable toxicity. These patients' direct DNA sequencing of tumor tissue EGFR exons 18-21 will be analyzed The response was evaluated by RECIST criteria after the patient received gefitinib 6 weeks.If the patients present with progress disease of brain metastasis after the therapy of gefitinib, the patients will receive irradiation of brain metastasis.If the response is stable disease,partial response or complete response,he will be examined by brain MRI every 12 weeks.