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.