Unexpected favorable response of stage IV gastric adenocarcinoma to sintilimab combined with chemotherapy: A case report

Gastric cancer is the fifth most common and the third deadliest type of cancer worldwide. Standard treatment protocols for advanced, unresectable or recurrent cases usually involve combination regimens. These regimens typically consist of a fluoropyrimidine and a platinum agent, with the anti‑HER2 monoclonal antibody trastuzumab added for HER2‑positive cases in the first line of treatment. In second‑line treatment, paclitaxel is used, sometimes in combination with ramucirumab. Despite these treatments, the median survival time for patients with advanced gastric cancer remains between 12 and 15 months, highlighting the need for innovative treatment options. Notably, immune checkpoint inhibitors have emerged as breakthrough treatments for various malignancies. These inhibitors allow immunotherapy to enhance traditional treatments such as surgery, chemotherapy, radiotherapy and targeted therapy. In this context, the present study describes a case of gastric adenocarcinoma that exhibited a favorable response to a combined regimen of chemotherapy and immunotherapy, specifically using sintilimab, a programmed cell death protein‑1 inhibitor. The patient with stage IV gastric cancer and peritoneal metastasis achieved a progression‑free survival of >5 years. This case underscores the potential for integrating new immunotherapeutic agents into existing treatment frameworks to markedly extend patient survival and improve quality of life.