The PACIFIC trial confirmed that the consolidation therapy with durvalumab in patients with stage III, locally advanced, unresectable NSCLC that had not progressed after definitive platinum-based chemoradiation therapy improved the progression-free survival (PFS) by about 17 months. However, in PACIFIC, no significant differences between durvalumab and placebo were observed in PFS. Unmet need remains in development of successful consolidation therapy following chemoradiation therapy in patients with EGFR-mutant stage III unresectable NSCLC. A recent ADAURA study showed that Osimertinib as an adjuvant therapy after surgery significantly prolonged disease-free survival in EGFR mutation-positive patients. Lazertinib, like Osimertinib, is a third-generation EGFR TKI agent and has shown excellent anticancer effects in preclinical studies and in early clinical settings. Based on these results of the 3rd generation EGFR TKI, Lazertinib, it is expected that there is a clinical benefit Lazertinib as consolidation therapy. This study aims to investigate the clinical benefits of Lazertinib (Trade name: LECLAZA Tab) consolidation therapy for patients with EGFR mutation-positive, unresectable stage III NSCLC after definitive platinum-based chemoradiation therapy.