Serplulimab combined with gemcitabine, nab-paclitaxel and stereotactic body radiotherapy as the first-line treatment for patients with metastatic pancreatic adenocarcinoma in China: a multicentre, single-arm, phase II trial (ICSBR) protocol

Introduction Patients with pancreatic ductal adenocarcinoma (PDAC) remain a poor prognosis despite the development of chemotherapy. Although programmed cell death 1 (PD-1) blockade has shown great efficacy in various solid tumours, its application in treating PDAC is limited. Recent studies have indicated that chemotherapy or stereotactic body radiotherapy (SBRT) may improve the antitumour effect of PD-1 blockade in patients with PDAC. The objective of this study is to evaluate the efficacy and safety of combined therapy comprising PD-1 blockade, gemcitabine plus nab-paclitaxel chemotherapy and SBRT for patients with metastatic PDAC. Methods and analysis This is a multicentre, single-arm, prospective phase II clinical trial. Forty-three patients diagnosed with metastatic PDAC will be enrolled. The eligible patients will be intravenously administered 1000 mg/m 2 gemcitabine and 125 mg/m 2 nab-paclitaxel on days 1 and 8 of the 21-day cycle. Serplulimab (200 mg) will be administered intravenously on day 1 of the 21-day cycle. Furthermore, during the second cycle, the patients will undergo SBRT with doses of 33 Gy in five fractions for primary lesions or doses of 24 Gy in three fractions for metastases. The primary endpoint is the 6-month progression-free survival (PFS) rate. The secondary endpoints overall survival, PFS, overall response rate, disease control rate, time to progression, duration of response, duration of disease control and safety. Moreover, this trial seeks to investigate biomarkers such as circulating tumour DNA and circulating hybrid cells in patients diagnosed with metastatic PDAC. Ethics and dissemination The study was approved by the Ethics Committee on Biomedical Research, West China Hospital of Sichuan University. The study results will be presented at international conferences and published in a peer-reviewed journal. Trial registration number ChiCTR2300073237.