Case 1. An 87-year-old man with a history of smoking of 45 pack-years presented with blood-tinged sputum. Chest computed tomography (CT) revealed a large mass (7 cm) in the left hilar region, which was lumped together with the left hilar lymph nodes. Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) was performed on the hilar lymph nodes, and poorly differentiated lung adenocarcinoma was confirmed by immunohistochemistry. Biomarker analysis was negative for epidermal growth factor receptor (EGFR) mutation and anaplastic lymphoma kinase (ALK) translocation, and PD-L1 was highly expressed (TPS: 90%). The clinical stage after a systemic evaluation was cT4N2M0, stage IIIB. Pembrolizumab monotherapy was initiated because the patient was not eligible for curative radiation. Although tumor progression was observed immediately before treatment, partial response (PR) was achieved after two treatment cycles, and CR was achieved after nine cycles. After 35 cycles of pembrolizumab, the patient was found to have maintained CR during treatment-free follow-up, and currently, the patient is alive 36 months after treatment initiation.