Study on the Efficacy and Safety of Neoadjuvant Radiotherapy Combined With Tislelizumab, Liposomal Irinotecan, and Capecitabine in the Treatment of pMMR Locally Advanced Rectal Adenocarcinoma With Low Rectal Involvement

Here is the updated format for the \*\*Eligibility Criteria\*\* with bullet points for each item: Inclusion Criteria: * Age: 18-75 years, no gender restriction * ECOG score 0-1 * Biopsy-confirmed pMMR (proficient mismatch repair) localized advanced low rectal adenocarcinoma (tumor's lower edge ≤ 10 cm from the anus) * Presence of the following high-risk factors: T3N+/T4/N2/EMVI+/MRF+/lateral lymph node metastasis/inability to undergo sphincter-preserving surgery * Routine chest and abdominal CT scans showing no distant metastasis * Bone marrow function: Neutrophil count (ANC) ≥ 1.5 × 10\^9/L, platelet count (PLT) ≥ 100 × 10\^9/L, hemoglobin (Hb) ≥ 70 g/L * Liver function: ALT, AST ≤ 2.5 × ULN (upper limit of normal); total bilirubin ≤ 1.5 × ULN; serum albumin ≥ 3 g/dL * Kidney function: Serum creatinine (Cr) ≤ 1.5 × ULN or creatinine clearance ≥ 60 ml/min (calculated using the Cockcroft-Gault formula) * For females and patients with reproductive potential, a negative pregnancy test must be done within 72 hours before starting the treatment, and the patient must agree to avoid pregnancy during the study treatment and for 6 months after the treatment. For males with reproductive potential partners, the patient must agree to use adequate medically approved contraception during and for 90 days after the final study treatment * Patients must agree to receive the study's neoadjuvant chemotherapy regimen and sign an informed consent form Exclusion Criteria: * Patients with a his…