Tumor recurrence after pathologic complete response in locally advanced gastric cancer after neoadjuvant therapy: case report and literature review

Abstract Most patients with gastric cancer are advanced at the time of diagnosis. Therefore, in order to improve the R0 resection rate, increase the PCR rate, and reduce the recurrence rate, different regimens have been tried to improve the perioperative treatment of advanced local gastric cancer. In recent years, immunotherapy has revolutionized cancer treatment. PD-1 and PD-L1 inhibitors have shown excellent efficacy in various tumors and have become potential therapeutic approaches after surgery, chemotherapy, radiotherapy, and targeted therapy. MSI-H/dMMR is a recognized marker for predicting the efficacy of immunotherapy for gastric cancer, and MSI-H/dMMR patients are more suitable for immunotherapy. However, the efficacy of immunotherapy alone in the treatment of gastric cancer is still unsatisfactory. We explore that combined immunosuppressive therapy may be valuable in improving the PCR rate of patients. Here, we report two female patients with gastric cancer defined as clinical stage (CT4N1-2M0), the detection of mismatch repair protein showed: dMMR (equivalent to MSI-H); PD-1 inhibitor combined with SOX (S-1 + oxaliplatin) in perioperative treatment obtained pCR, suggesting that PD-1 inhibitor combined with chemotherapy provides a more strategic choice for comprehensive perioperative treatment of gastric cancer. It is controversial for PCR patients to continue comprehensive chemotherapy or clinical observation after surgery. Surprisingly, two patients underwent clinical observation after surgery but developed different degrees of metastasis at about six months after surgery. Therefore, we reviewed the comprehensive perioperative treatment of two patients, hoping to provide some reference value for clinical decision-making.