Preoperative short‐course radiotherapy followed by chemotherapy and PD‐1 inhibitor administration for locally advanced rectal cancer: A study protocol of a randomized phase II/III trial (STELLAR II study)

AIM: For patients with locally advanced rectal cancer, previous STELLAR studies have shown that a new adjuvant treatment paradigm of short-course radiotherapy followed by neoadjuvant chemotherapy can achieve pathological complete response rates superior to those of standard care; however, the 3-year DFS is inferior to neoadjuvant concurrent radiotherapy. Recent studies have shown that immune checkpoint inhibitors may improve the prognosis of rectal cancer and have good synergy with radiotherapy. Therefore, neoadjuvant chemotherapy combined with immune checkpoint inhibitors after a short course of radiotherapy has the potential to further improve complete response rates and prognosis. METHOD: The STELLAR II study is a multicentre, open label, two-arm randomized, phase II/III trial of short-course radiotherapy followed by neoadjuvant chemotherapy concurrent with immunotherapy for locally advanced rectal cancer. A total of 588 patients with locally advanced rectal cancer (LARC) will be randomly assigned to the experimental and control groups. The experimental group will receive short-course radiotherapy and neoadjuvant chemotherapy in combination with sindilizumab, while the control group will receive short-course radiotherapy and neoadjuvant chemotherapy. Both groups will subsequently receive either total rectal mesenteric resection or a watch & wait (W&W) strategy. The phase II primary endpoint is the complete remission rate, and the secondary endpoints include grade 3-4 adverse events, perioperative complications, R0 resection rate, overall survival, local recurrence rate, distant metastasis rate and quality of life score. A seamless phase II/III randomized controlled design will be used to investigate the effectiveness and safety of the TNT strategy with the addition of immunotherapy. The trial opened, and the first patient was recruited on 31 August 2022. Trial registration number and date of registration: ClinicalTrials.gov NCT05484024, 29 July 2022. DISCUSSION: The STELLAR II trial will prospectively evaluate the efficacy of TNT treatment strategies that incorporate immune checkpoint inhibitors. The trial will yield important information to guide routine management of patients with local advanced rectal cancer.