Neoadjuvant serplulimab in combination with concurrent chemoradiotherapy for locally advanced, resectable esophagogastric junction adenocarcinoma.

Abstract

e16103 Background: Surgery combined with perioperative therapy was recommended as standard treatment for patients with locally advanced esophagogastric junction (EGJ) adenocarcinoma, but the survival rate was still poor. Immunotherapy has shown antitumor activity and an acceptable safety profile in advanced EGJ cancer. The aim of this study was to evaluate the efficacy and safety of neoadjuvant Serplulimab combined with concurrent chemoradiotherapy in previously untreated locally advanced resectable EGJ adenocarcinoma. Methods: Eligible patients with resectable EGJ(Siewert Type II and Type III, Siewert classification 2000)adenocarcinoma stage cT3-4 or N+ were enrolled. Patients received neoadjuvant Serplulimab (300mg on day 1) plus SOX(oxaliplatin at 130mg/㎡on day 1; TS1 40-60mg two times per day on D1-D14, Q3W) in first cycle, followed by Serplulimab (300mg on day 1) combined with concurrent chemoradiotherapy (Reduced SOX regimen: oxaliplatin at 100mg/㎡on day 1, TS1 40-60mg two times per day on D1-D14, Q3W; Radiotherapy dose:45Gy in 25f) in second and third cycle. The patient finished the preoperative treatment and rested for 6-8 weeks for surgery. The primary endpoint was pathological complete response (pCR) rate. Secondary endpoints were major pathological response(MPR) rate, R0 resection rate, objective response rate(ORR), disease-free survival(DFS), overall survival(OS), and toxicity. Results: From March 8, 2023 to January 31,2024,15 patients were enrolled. Nine patients completed neoadjuvant therapy. Eight of these patients underwent radical surgical resection. One out of nine achieved a confirmed pathological complete response (pCR) after three cycles of neoadjuvant treatment. Additionally, two out of nine patients achieved major pathological response(MPR). So, the pCR rate was 11.1%, and the MPR rate was 22.2%. The Tumor and Lymph Nodes downstaging rates are 62.5% and 87.5%, respectively. The median DFS and OS were not reached. In terms of safety, fifteen patients who received at least one cycle of neoadjuvant therapy were included. The most common treatment-related adverse events(TRAE) across all grades were nausea/vomiting(6/15), anorexia(5/15), thrombocytopenia(4/15), and fatigue(4/15). Four patients (26.7%) had grade≥3 adverse events during preoperative therapy, with thrombocytopenia(3/15) and hepatic veno-occlusive disease(1/15). Immune-related adverse reactions(irAE) included myositis(1/15) and rash(1/15), both were grade 1. No grade 4 or higher TRAEs were observed. Conclusions: Initial benefits were demonstrated when using Serplulimab with concurrent chemoradiotherapy for the treatment of locally advanced, resectable EGJ adenocarcinoma patients. The efficacy and safety of Serplulimab with chemoradiotherapy will be further investigated in this trial later. Clinical trial information: NCT05918419 .