What happened, in summary

An 81-year-old man was diagnosed with Stage IV gastric cancer after endoscopy found a bleeding tumor in the gastric fundus and imaging showed multiple liver metastases. Biopsy showed a tumor with two components: moderately differentiated adenocarcinoma and a poorly differentiated component with strong neuroendocrine features consistent with large cell neuroendocrine carcinoma. The tumor was HER2 1+, had intact mismatch-repair proteins, and had a PD-L1 tumor-cell score of 5%. Because of his age, diabetes, coronary disease, chronic kidney disease, and impaired liver and kidney function, he started nivolumab alone rather than combination chemotherapy. After more than 4 months, imaging showed marked shrinkage of the liver metastases and reduction of the gastric mass. He then developed jaundice and worsening liver tests. Nivolumab was stopped after severe immune-mediated hepatitis was diagnosed, and immunosuppressive treatment improved his symptoms and liver tests. His condition later worsened. By early October 2024, cancer progression and multi-organ failure were documented, and his family decided to discontinue treatment. His course combined a meaningful early response to immunotherapy with a serious immune-related liver complication and subsequent cancer progression.