Paclitaxel/Carboplatin (PC) Followed by Gefitinib Versus PC in Advanced Non-small Cell Lung Cancer

Inclusion Criteria: * More than 18 years of age * Histologically documented non-small cell lung cancer with metastasis (Stage IV) or locally advanced (Stage IIIB) with malignant effusion. * At least 1 measurable lesion as defined by RECIST1.0. All target lesions must have a unidirectional diameter of at least 1cm. Baseline measurements must be compared within 4 weeks prior to enrollment. * ECOG PS 0-2 * At least 1 week since the last radiotherapy. Patients must have recovered from all acute toxicities from radiotherapy. * Patients must have adequate hematologic, renal and liver function as defined by Hb \> 9g/dL, neutrophils \> 1000/mm3, platelets \> 50,000/mm3, creatinine \< 2mg/dL, and AST (SGOT) and/or ALT (SGPT) \< 5 x UNL (upper normal limit). * Willingness and ability to comply with scheduled visits, treatment plans, laboratory tests and other study procedures. * Written and voluntary informed consent understood, signed and dated. Exclusion Criteria: * Patients with tumor harboring EGFR mutation. * Prior systemic therapy for NSCLC * Non-smoking patients with adenocarcinoma. But if those patients show wild type EGFR, they are eligible to this study. * Symptomatic brain metastasis. Brain metastases stable \< 2 weeks before dosing or requiring concurrent steroid treatment or with clinical symptoms. * Major surgery within 3 weeks prior to study enrollment. * Previous (less than 3 years ago) or current malignancies at sites other than curatively treated in situ carcinoma of cervix, or basal or squamous cell carcinoma of the skin. * Severe medical illness or active infection that would impair the ability to receive gefitinib. * Pregnancy or breast feeding.