Lazertinib for NSCLC Harboring Activating EGFR Mutations in TKI naïve Patients

Inclusion Criteria: * Histologically or cytologically confirmed locally advanced or metastatic non-small cell lung cancer which is not amenable to treatment with a curative aim (e.g. surgery or radiation). Patients who underwent curative intent surgery or definitive CRT and experience recurrence after 6 months are eligible. * Stage IIIC or IV by AJCC 8th edition * Confirmed EGFR mutations (exon 19 deletion, L858R)(The result from both cell-free DNA or tissue-based DNA from the local test is allowed.) * Age of 19 or more. * Performance status of Eastern Cooperative Oncology Group 0 to 2. * Expected minimum life expectancy of 12 weeks * Adequate organ function. * Available to provide the adequate tissue and blood for the genomic tests- At least 15 unstained slide and 20 cc of blood at baseline (mandatory) and disease progression. * Agreed to perform re-biopsy at the timepoint of disease progression. * At least two weeks after the chemotherapy * Female subjects must either be of non-reproductive potential * Subject willing and able to comply with the protocol * Signed written informed consent Exclusion Criteria: * Previously treatment with any kind of EGFR TKI (Previously chemotherapy treated patients is allowed) * Any concurrent and/or other active malignancy that has required systemic treatment within 2 years of first dose of study drug. (allowed for participation if investigator decided that previous malignancy is cured and not need for any additional treatment) * Uncontrolled central nervous system metastases- patient with asymptomatic brain metastases or CNS symptom manageable with TKI and evaluated by investigator can be enrolled. * Spinal cord compression, leptomeningeal carcinomatosis * Uncontrolled systemic illness, including uncontrolled hypertension, active bleeding, or active infection * Radiotherapy with a wide field of radiation within 2 weeks or radiotherapy with a limited field of radiation (localized radiotherapy or gamma knife surgery) for palliation within 1 week * Any unresolved toxicities from prior therapy, greater than CTCAE grade 1 * Mean QT interval corrected for heart rate (QTc) ≥ 470 ms * No measurable lesion * Unable to swallow the product due to refractory nausea, vomiting or chornic gastrointestinal disease.