This clinical trial aims to evaluate the efficacy and safety of Kangfupen (a topical liquid dressing) in treating chronic radiation-induced proctitis (RTOG Grade 2 or higher). The key questions we aim to answer are:

1. Does Kangfupen improve LENT-SOMA rectal injury scores after 3 months of treatment?
2. Does Kangfupen reduce endoscopic inflammation (Vienna score) and symptoms (RTOG/CTCAE grades)?
3. What adverse events occur with Kangfupen therapy? Kangfupen liquid dressing (50 mL/once daily) will be administered as retention enema for 3-6 months, adjusted based on lesion location.

Researchers will evaluate the following outcomes to assess Kangfupen's efficacy and safety in treating chronic radiation proctitis:

1. Change in LENT-SOMA rectal injury score (baseline vs. 3 months).
2. Changes in Vienna endoscopic score, RTOG/CTCAE grades, and IBDQ quality-of-life scores.
3. Symptom improvement rate and time to complete remission.

Participant will:

1. Undergo baseline and 3-month endoscopic evaluations.
2. Complete symptom diaries and quality-of-life questionnaires.
3. Attend regular clinic visits for safety monitoring.

Baseline Assessments

All enrolled patients must complete the following evaluations:

1. Medical history including primary tumor type, histopathology, staging and radiotherapy details (timing, technique, and total dose)
2. Physical examination
3. ECOG performance status
4. Laboratory tests including complete blood count, stool occult blood, liver/kidney function and tumor markers
5. Pelvic scans to exclude tumor recurrence/progression
6. Full colonoscopy with photographic documentation. Images every 5cm from anus to splenic flexure, and at sites of severe mucosal reaction additionally
7. Grading based on LENT-SOMA, RTOG, and CTCAE v5.0 criteria

Treatment protocol Kangfupen (liquid dressing) retention enema

• Dosage: 50 mL once daily for 3-6 months

• Administration depth: Determined by colonoscopy findings Enema preparation & administration 1. Reconstitution:

  1. Transfer liquid from plastic to brown glass vial
  2. Shake vigorously to dissolve lyophilized powder
  3. Return solution to plastic bottle and shake again 2. Delivery:
  1. Position: Left lateral decubitus with waste basin
  2. Slowly instill 50 mL into rectum
  3. Retain for ≥30 minutes, rotating positions every 15 minutes (left/right lateral, supine, knee-chest)

Concomitant therapies Permitted: probiotics, smectite, antibiotics, stool softeners Prohibited: 5-ASA drugs (mesalazine/sulfasalazine), endoscopic hemostasis (e.g., argon plasma coagulation), formaldehyde/HBO/surgery/fecal microbiota transplant, other enema therapies.

Toxicity monitoring Potential adverse events include allergic reactions and mechanical injury (bleeding/perforation). Required Actions include immediately discontinuing treatment and reporting to the principal investigating site within 24 hours.

All adverse events will be assessed using CTCAE v5.0 criteria.

Follow-up schedule Month 1-2: LENT-SOMA, RTOG/CTCAE grades, IBDQ, symptom improvement evaluation Month 3: Above + sigmoidoscopy with Vienna scoring Every 6 months after month 6: sigmoidoscopy + all scales + physician's global assessment of treatment efficacy

Inclusion Criteria:

• Fully voluntary with decision-making capacity
• 18-80 years old
• Completed pelvic radiotherapy for malignancy ≥3 months prior
• Evidence of chronic radiation-induced rectal injury (RTOG Grade ≥2)
• Evidence of radiation-induced rectal injury on colonoscopy (within 3 months, Vienna endoscopic score ≥1)
• No prior surgery
• ECOG score 0-2
• Estimated survival ≥1 year

Exclusion Criteria:

• Primary rectal tumours or pelvic malignancies with rectal involvement
• Uncontrolled, recurrent, or metastatic tumours
• Concurrent anticancer therapies including radiotherapy, chemotherapy, targeted therapy, immunotherapy and traditional Chinese medicine with anti-tumour properties
• Patients with intestinal fistula, perforation, or obstruction
• History of electrocautery treatment within 1 month
• Recent medication use (within 2 weeks): traditional Chinese medicine enemas, mesalazine (oral or rectal) and other anti-inflammatory bowel medications
• History of superoxide dismutase allergy
• Pre-existing chronic colitis, ulcerative colitis, or nonspecific proctitis
• Connective tissue diseases requiring long-term corticosteroid therapy
• Pregnant or lactating women
• Active infection or fever
• Other severe comorbidities potentially affecting trial compliance: unstable cardiac disease requiring treatment, renal disorders, chronic hepatitis, poorly controlled diabetes and psychiatric illnesses