Case Report: Sustained complete response achieved in a patient with advanced HER-2 positive gastric cancer after 4 years of chemotherapy-free treatment.

Background: Gastric cancer ranks fifth in both global incidence and mortality rates, with over half of the newly diagnosed cases worldwide occurring in China. Most patients are diagnosed at advanced stages, making surgical resection unfeasible. As a result, current treatment primarily relies on chemotherapy-based multimodal therapies. However, with ongoing research, chemotherapy-free treatment strategies are gaining increasing attention and have emerged as a promising avenue for the treatment of gastric cancer. Case presentation: A 42-year-old male was diagnosed with stage IV gastric adenocarcinoma and multiple liver metastases due to abdominal bloating. The patient was enrolled in a clinical study and received a combination of KN026 and KN046 targeted therapy with immunotherapy. After two years of treatment, a complete response was achieved. Conclusions: The combination of anti-HER-2 bispecific targeting therapy and PD-1/CTLA-4 bispecific immunotherapy demonstrated promising efficacy and a favorable safety profile in this patient with advanced HER2-positive gastric cancer, achieving durable complete response without chemotherapy. This case provides a rationale for further exploring chemotherapy-free strategies using dual bispecific antibodies in carefully selected patients.