SCRT-NALIRIXELOX+Sintilimab as TNT for High-Risk LARC

This is a single-center, exploratory clinical study for patients with newly diagnosed, high-risk, locally advanced rectal cancer. The study aims to evaluate the effectiveness and safety of a comprehensive pre-surgery (neoadjuvant) treatment strategy. All participants will receive a short course of radiation therapy (25 Gy in 5 fractions) over one week. This will be followed by a combination of chemotherapy (Liposomal Irinotecan, Oxaliplatin, and Capecitabine) and immunotherapy (Sintilimab). This combined treatment is administered for six cycles. For patients who achieve a complete response, the option to avoid immediate surgery and enter a close monitoring program ("Watch and Wait") will be considered.