[Analysis of the efficacy and safety of preoperative programmed death protein-1 inhibitor combined with chemotherapy in immunotherapy-sensitive patients with locally advanced gastric cancer or adenocarcinoma of the esophagogastric junction].

Objective: To evaluate the short-term efficacy and safety of a preoperative combination of programmed cell death protein-1 (PD-1) inhibitor with either oxaliplatin + capecitabine (CapeOx) or oxaliplatin + tegafur gimeracil oteracil potassium (SOX) in the treatment of locally advanced immunotherapy-sensitive gastric cancer (LAGC) or adenocarcinoma of the esophagogastric junction (AEG). Methods: The cohort of this retrospective descriptive case series comprised patients with LAGC or AEG whose cancers had been determined to be immunotherapy- sensitive by endoscopic biopsy before treatment in the Gastrointestinal Cancer Center, Unit III, Peking University Cancer Hospital and Institute from 1 August 1 2021 to 31 January 2024. Patients with any one of the following three characteristics were immunotherapy-sensitive: (i) PD-L1 combined positive score (CPS) ≥5; (ii) microsatellite instability-high (MSI-H) / mismatch repair deficiency (dMMR); or (iii) Epstein-Barr virus-encoded RNA (EBER) positivity. All study patients received PD-1 inhibitors combined with CapeOx or SOX as a neoadjuvant or conversion treatment strategy before surgery. Patients with immune system diseases, distant metastases, or human epidermal growth factor receptor 2 positivity were excluded. Factors analyzed included pathological complete response, clinical complete response, major pathological response, R0 resection rate, surgical conversion rate, and safety of the treatment, including immune-related adverse events (irAEs) and surgical complications. Results: The study cohort comprised 39 patients (28 men and 11 women) of median age 62 (range 44-79) years. After the above-described preoperative treatment, radical resection of the 14 tumors that were initially considered unresectable was achieved (surgical conversion rate: 14/14). Twenty-three of the remaining 25 patients underwent radical resection. The last two patients achieved clinical complete responses and opted for a "non-surgical strategy" (watch and wait). Overall, 37 patients (94.9%) underwent radical resection, with an R0 resection rate of 100% (37/37), pathological complete response rate of 48.6% (18/37), and major pathological response rate of 62.2% (23/37). Of the 24 patients with CPS ≥ 5 (non-MSI-H/dMMR and non-EBER positive), 11 achieved pathological complete responses and one with CPS=95 achieved a clinical complete response. Of the eight patients with MSI-H/dMMR, six achieved pathological complete responses and one a clinical complete response. Of the seven patients with EBER positivity, one achieved a pathological complete response. After excluding patients with major pathological complete responses, there was a statistically significant difference in CPS scores between preoperative biopsy specimens and postoperative surgical specimens in 13 patients (7.769±5.570 vs. 15.538±16.870, t=2.287, P=0.041). All patients tolerated preoperative immunotherapy well; nine patients (9/39, 23.1%) had Grade I-II irAEs. There were no Grade III-IV irAEs. The five patients with pyloric obstruction before treatment tolerated normal diets after treatment. The incidence of postoperative complications among all patients who underwent surgery was 18.9% (7/37), including one case of Grade IIIA anastomotic leakage, one of Grade IIIA intestinal obstruction, one of Grade II abdominal hemorrhage, two of Grade II abdominal infection, one of Grade I intestinal obstruction. Additionally, one patient developed COVID-19 postoperatively. All patients recovered with symptomatic treatment. Conclusion: We found that preoperative treatment of patients with LAGC or AEG of one of three types (CPS≥5, dMMR+MSI-H, and EBER positivity) with a PD-1 inhibitor combined with CapeOx or SOX chemotherapy achieved promising effectiveness and safety, with high surgical conversion, R0 resection, and complete response rates.