Stage IIIA small-cell lung cancer with anti-NMDAR encephalitis: initial complete response, recurrence, and death

What happened, in summary

This 66-year-old man was transferred while comatose after 3 weeks of rapidly progressive memory impairment, agitation, fever, and impaired consciousness. He had type 2 diabetes and a myocardial infarction 10 years earlier. Brain MRI was unremarkable, EEG showed generalized rhythmic delta activity, and cerebrospinal fluid had elevated white blood cells but no malignant cells. Chest CT showed a left upper-lobe abnormality, and autoimmune/paraneoplastic encephalitis was suspected. He received methylprednisolone 1000 mg for 3 days, then prednisolone sodium succinate 40 mg daily, but he remained in coma with apnea episodes, fist clenching, and involuntary rocking movements. Bronchoscopy diagnosed small-cell lung cancer, cT3N1M0 / Stage IIIA. His cerebrospinal fluid was later positive for anti-NMDAR antibodies, confirming paraneoplastic anti-NMDAR encephalitis. Despite performance status 4 and coma, his team started carboplatin 600 mg, etoposide 130 mg, and atezolizumab 1200 mg after careful discussion. The neurologic response was striking: consciousness improved by day 3, and involuntary movements stopped completely by day 10. Follow-up CT at 2 months showed complete response. After 3 months of rehabilitation, he could perform activities of daily living independently and was discharged. Seven months later, the primary lung lesion recurred, but the encephalitis did not recur. He continued lung cancer treatment until he died, 21 months after disease onset. His story shows a dramatic early neurologic and tumor response followed by lung cancer recurrence and death. The neurologic syndrome remained controlled after chemotherapy eliminated the antibody-producing tumor component, but the cancer itself later returned and drove the final outcome despite continued treatment.