Neoadjuvant Cadonilimab Plus Chemotherapy Following Short-Course Radiotherapy in Locally Advanced 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.