What happened, in summary

This 63-year-old man with a 40 pack-year smoking history was admitted in April 2021 with 3 weeks of sharp left-sided chest pain. CT showed a large left pleural effusion causing partial lung collapse, left lung consolidation, and a soft-tissue mass near the left lower hilum. Tumor markers were markedly elevated in blood and pleural fluid, and pleural drainage improved his symptoms. Bronchoscopy did not yield malignant tissue, so video-assisted thoracoscopic exploration with wedge resection of chest wall and pulmonary lesions was performed. Pathology confirmed poorly differentiated lung adenosquamous carcinoma. Immunohistochemistry showed markers of both adenocarcinoma and squamous differentiation, including TTF-1, Napsin A, p63, and CK5/6. The chest wall lesion was metastatic pulmonary adenosquamous carcinoma. Imaging also showed cervical and axillary lymph-node involvement, and the cancer was staged cT4N3M1b, Stage IVA. Molecular testing found KRAS G12C, BRAF G466R, PIK3CA H1047R, and FLT1 L1232F mutations. PD-L1 was positive with TPS 18.11%, tumor mutation burden was 3.7 mut/Mb, and MSI status was low. Treatment began on May 14, 2021 with paclitaxel, nedaplatin, and tislelizumab every 3 weeks. He completed 6 cycles by September 5, 2021. Symptoms improved, tumor markers fell, pulmonary and pleural lesions resolved, and cervical/axillary nodes normalized, meeting RECIST complete remission. Maintenance tislelizumab continued from September 29, 2021 through April 2023. As of March 30, 2025, he maintained complete response with no radiologic progression or recurrence and progression-free survival of 46.5 months. The durable response followed a finite 6-cycle combination course and maintenance tislelizumab rather than long-term cytotoxic chemotherapy.