This prospective, single-center, randomized controlled trial aims to assessing the efficacy and safety of neoadjuvant chemoradiation plus Tislelizumab (PD-1 inhibitor) with or without Probio-M9 and subsequent TME surgery, by comparing assorted endpoints between two experiment groups (Experiment group 1: chemoradiation+PD-1 inhibitor+Probio-M9; Experiment group 2: chemoradiation+PD-1 inhibitor+placebo) with a control group (chemoradiation only).
Age ≥ 18 years
ECOG performance status 0-2
Biopsy-proven rectal adenocarcinoma
Distal tumor margin within 10 cm of the anal verge
History of multiple primary cancers or concomitant malignant tumors other than rectal cancer
Receipt of any anti-cancer treatment (e.g., surgery, chemotherapy, radiotherapy, or other systemic therapies) within the past 5 years
History of recent major surgery
Conditions that may affect the gastrointestinal absorption of capecitabine (e.g., inability to swallow, persistent nausea or vomiting, chronic diarrhea)