Long-term synchronous chemoradiation (CRT) with sequential TME is the treatment recommended by current guidelines for locally advanced rectal cancer (LARC). The latest STELLAR study showed that preoperative short-course radiotherapy (SCRT) combined with preoperative chemotherapy is safe and effective and can be used as an alternative to conventional CRT in LARC [1]. In recent years, new therapies blocking immune checkpoints (cytotoxic T lymphocyte-associated molecular protein 4 (CTLA-4), programmed cell death 1 (PD1) and programmed cell death ligand 1 (PD-L1)) have achieved landmark achievements in the field of cancer therapy. Several clinical trials are evaluating the efficacy of a combination of RT and immune checkpoint inhibitors (ICIs) in rectal cancer (NCT02948348, NCT04124601, NCT04558684). The results of the study suggest that radioimmunotherapy is safe and effective in rectal cancer. A number of studies have shown that combined PD-1 and CTLA-4 blockade is associated with a higher response rate whereas more toxicities in multiple tumor types. Cadonilimab is a tetrameric PD-1/CTLA-4 bispecific antibody, based on the Akeso Tetrabody platform. It introduces novel T cell targeting mechanisms of action that may provide an improved therapeutic index and a favorable toxicity profile compared to PD-1 and CTLA-4 combination therapy. The study of SCRT combined with Cadonilimab and chemotherapy in middle and lower LARC has not been reported at home or abroad.~Therefore, this study plans to recruit 27 patients with middle and lower LARC to explore the efficacy and safety of radiation of 5 Gy for 5 days followed by Cadonilimab 6mg/kg plus mFOLFOX6 (oxaliplatin 85 mg/m2, leucovorin 400 mg/m2, 5-fluorouracil bolus 400 mg/m2 on day 1, and 5-fluorouracil infusion 2400 mg/m2 for 48 h) every 2 weeks for total 6 cycles preoperatively. The primary endpoint is the pathological complete response (pCR) after surgery. The secondary endpoints consist of a clinical complete response (cCR), major pathological response (MPR), objective response rate (ORR), recurrence-free survival (RFS), overall survival (OS) and safety. Clinical response was evaluated by endoscopy, digital rectal examination and pelvic MRI. Safety was analyzed in all patients who receive at least one dose of treatment. The exploratory endpoint covers the quality of life.~After surgery, non-pCR patients receive adjuvant Cadonilimab combined with mFOLFOX6 for 6 cycles while pCR ones have two options: adjuvant treatment which is the same as the neoadjuvant regimen or observation. As for cCR patients, TME or transanal local excision is one of options while the watch and wait (W&W) strategy can also be considered especially for ultra-low rectal cancer.
The goal of this clinical trial is to test the efficacy and safety in patients with locally advanced middle and lower rectal cancer. The main questions it aims to answer are:• Whether Cadonilimab combined with chemotherapy following short-course radiation can improve pathological complete response(pCR) rate? •Are the toxicities of the combination therapy manageable? Participants will be given radiation of 5 Gy for 5 days and then neoadjuvant Cadonilimab combined with modified fluorouracil, leucovorin, and oxaliplatin (mFOLFOX6) for 6 cycles. Without progressed disease, total mesorectal excision (TME) or transanal local excision will be performed. If clinical complete response was received, watch and wait strategy is one of choices. Adjuvant Cadonilimab plus mFOLFOX6 for another 6 cycles could be suggested for non-pCR participants,while surveillance is also suitable for pCR ones.