A Prospective, Single-Arm Clinical Study of a Dietary Supplement for the Prevention of Acute Radiation-Induced Rectal Injury During Neoadjuvant Chemoradiotherapy for Rectal Cancer

Inclusion Criteria: 1. Histologically confirmed rectal adenocarcinoma. 2. Clinically staged as locally advanced rectal cancer (cT3-4 and/or N+). Planned to receive short-course radiotherapy or long-course radiotherapy combined with concurrent fluoropyrimidine-based chemotherapy. 3. ECOG performance status of 0 or 1. 4. Baseline defecation frequency \< 3 times/day, with no significant abdominal pain or tenesmus. Exclusion Criteria: 1. Previous history of total mesorectal excision (TME) or other intestinal resection surgeries. 2. Diagnosis of severe diarrhea, Crohn's disease, ulcerative colitis, or chronic radiation enteritis. 3. Previous history of pelvic radiotherapy. 4. Presence of malignant pleural effusion or malignant ascites, or complete/incomplete intestinal obstruction, rendering the patient unable to tolerate dietary supplement therapy. 5. Participation in other investigational drug trials within 4 weeks prior to enrollment. 6. Receiving non-conventional chemotherapy regimens (non-fluoropyrimidine drugs) or concurrent participation in other trials involving potent mucosa-damaging drugs. 7. Pregnant or breastfeeding women. 8. History of alcoholism, drug abuse, or substance abuse within the past 1 year. 9. History of severe allergies or known allergy to the ingredients of the dietary supplement.