Poziotinib in Stage IV Lung Adenocarcinoma With HER2 Mutation (KASTT001)

Inclusion Criteria: 1. lung adenocarcinoma, stage IV 2. Patients with HER2 mutation by sequencing \- Confirmed triple-negative patients with remnant tumor DNA 3. Patients who have histories of previous exposure to at least one more systemic chemotherapies (not EGFR-TKI) 4. ECOG performance status 0\~2 5. Patient with at least one measurable lesions according to RECIST 6. Patients who have proper organ functions as follows * Neutrophil count: \> 1,500/uL * Platelet count: \> 100,000/uL * Hb: \> 9.0g/dL * AST/ALT : \< 2.0 x upper normal limit * Bilirubin: \< 1.25 x upper normal limit * Serum creatinine : \< upper normal limit Exclusion Criteria: 1. Expected lie expectancy \< 3 months 2. CNS metastasis or spinal cord compression which were not treated with operation and/or radiation therapy(but, Patient with medically stable condition after operation and/or radiation therapy, or without symptomatic metastasis of brain in accordance with the investigator's judgment could participate in the study) 3. Patients who have severe or unstable systemic disease in accordance with the investigator's judgment(ex, unstable or uncompensated respiratory, cardiac, hepatic or renal disease) 4. Patients who have histories of previous exposure to EGFR-TKI