A Study Comparing Pemetrexed Plus Cisplatin Versus Pemetrexed Alone in NSCLC Patients Who Have Progressed on First Line EGFR-TKI

Inclusion Criteria: * Histologically confirmed nonsquamous NSCLC with activating EGFR mutation (on exon 19 deletion or exon 21 L858R mutation) * Stage IIIb, IV or recurrent NSCLC (AJCC 7th criteria) * Age ≥ 20 years * ECOG performance status of 0 or 1 * At least one measurable lesion by RECIST 1.1 * Progression after first line treatment with EGFR TKIs for advanced NSCLC * Asymptomatic brain metastasis or symptomatic brain metastasis treated with local treatment such as operation, whole brain radiotherapy, or gamma-knife surgery * At least 2 weeks later after whole brain radiotherapy or palliative radiotherapy * Adequate renal function: estimated creatinine clearance ≥ 45 mL/min * Organ function as evidenced by the following; Absolute neutrophil count \> 1.5 x 109/L; platelets \> 100 x 109/L; total bilirubin ≤1.5 UNL; AST and/or ALT \< 3 UNL, in case of known hepatic metastasis, AST/ALT\< 5 UNL * Written informed consent form * No other previous systemic chemotherapy Exclusion Criteria: * Uncontrolled systemic illness such as DM, CHF, unstable angina, hypertension or arrhythmia * Patients with post-obstructive pneumonia or uncontrolled serious infection * Pregnant or nursing women (Women of reproductive potential have to agree to use an effective contraceptive method) * Uncontrolled symptomatic brain metastasis * Presence of third space fluid which cannot be controlled by drainage * Prior history of malignancy within 5 years from study entry except for adequately treated basal cell or squamous cell skin cancer or in situ cervical cancer, well-treated thyroid cancer.