What happened, in summary

A 65-year-old man was admitted in January 2022 after 2 weeks of worsening right-sided arm and leg weakness. His ECOG performance status was 1 at presentation. Brain MRI showed a 20 x 19 mm lesion in the medial left parietal lobe, and chest CT showed a mass in the upper lobe of the right lung with multiple satellite lesions. Because the brain lesion was causing progressive neurologic symptoms and mild right-sided hemiparesis, he underwent neuronavigation-guided intracranial tumor resection and cranioplasty. Pathology confirmed metastatic pulmonary adenocarcinoma, a form of non-small cell lung cancer that had spread to the brain. Immunohistochemistry supported lung origin, including CK7, TTF-1, and Napsin A positivity. PD-L1 testing was very high, with CPS 98 and TPS 95%. The tumor had no EGFR gene mutation and no ALK rearrangement, so EGFR- or ALK-directed targeted therapy was not indicated. He was diagnosed with Stage IVA metastatic NSCLC. Three weeks after brain-metastasis resection, the right lung lesion measured 47 x 45 mm. Given the high PD-L1 expression, he started zimberelimab, a PD-1 inhibitor, at 240 mg IV every 3 weeks in late February 2022. After 4 cycles, the lung lesion decreased to 27 x 21 mm, meeting partial response, and brain MRI showed no recurrent brain metastasis. He continued zimberelimab for 31 cycles from February 2022 through January 2024. As of March 2024, he had 24 months of progression-free survival and intracranial recurrence-free survival, no evidence of brain recurrence, controlled lung disease, and normal quality of life, without reported treatment-limiting toxicity or neurologic decline.