MSI-High Gastric Cancer With a Complete Response to Preoperative Nivolumab

What happened, in summary

A 64-year-old woman sought care in March 2019 after months of severe fatigue, shortness of breath, and chest pain. Her hemoglobin was 54 g/L. Endoscopy showed an ulcerated pyloric tumor, and biopsy identified poorly differentiated gastric adenocarcinoma. The tumor was MSI-high, expressed PD-L1 in more than 1% of cells, and was HER2 negative. Imaging showed a mass measuring about 60 × 54 × 44 mm with small infrapyloric lymph-node metastases but no distant spread. The cancer was staged as cT3N1M0, stage III.

She was reluctant to receive standard cytotoxic chemotherapy and strongly preferred a newer treatment. After informed consent, she started nivolumab on June 14, 2019, at 3 mg/kg every 14 days. Six infusions were completed without clinically significant side effects. CT after 4 cycles showed a clear partial response and substantial tumor shrinkage.

In November 2019, she underwent diagnostic laparoscopy followed by distal subtotal gastrectomy. Pathology found no residual cancer cells in the removed stomach tissue. All 12 examined lymph nodes were also free of cancer, although 2 showed fibrosis consistent with treatment response. She described feeling well during immunotherapy and was relieved that the tumor had disappeared. At the time of reporting, she had no symptoms and had returned to her normal daily activities.