Complete Remission of a Patient With HER-2 amplification Gastric Cancer Treated With Sintilimab Combined With Trastuzumab

Abstract Background Gastric cancer (GC) is one of the most common malignant tumors in China and is also a major cause of cancer deaths worldwide, for which treatment strategies are extremely limited. Patients Susually lose the opportunity of therapeutic surgery because the lesions cannot be completely removed, although it can greatly prolong their survival time. Human epidermal growth factor receptor-2（HER-2）is the diagnostic criterion that determines whether patients can be the therapy with target in gastric cancer. However, the effect of targeted therapy on improving patient over survival (OS) is not significant. In recent years, immune checkpoint inhibitors (ICIs) sintilimab has shown significant efficacy in the treatment of gastric cancer. Case presentation A 50-year-old man was diagnosed with adenocarcinoma of GC with multiple lymph node metastases. Positron emission tomography-computed tomography (PET-CT) shows retroperitoneal, ileocecal, ascending colon, pelvic peritoneum, and mesangial metastasis. Then, the patient underwent genetic testing.The results indicated that MSS, PD-L1 CPS = 2, HER-2(3+). Therefore, the first choice was chemotherapy combined with immunotherapy and targeted therapy. The regimen was chosen with sintilimab plus trastuzumab with chemotherapy SOX as first-line therapy for patients. After two cycles of treatment, the expression of CA199 was decreased, and lymph node metastases were smaller than before. The treatment was continued, and CT scans suggested complete response (CR) was achieved for both the lymph node metastases and gastric lesions after of 4 cycles treatment on 31 January 2023. Maintenance sintilimab plus trastuzumab was selected because of his stable CR status. During the treatment period, there was no occurrence of relatively serious adverse effects due to chemotherapy. Conclusion HER-2-positive GC of patients who receives target combined with immune therapy may be an efficient and safe decision-making therapeutic choice. The case provides a treatment regimen for patients with HER-2-positive, whether to choose combination therapy as a new treatment regimen. This is the first reported case of gastric cancer with multiple lymph node metastases with complete remission with sintilimab plus trastuzumab.