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Background Radiation enteritis (RE) is a common and severe complication after radiotherapy for abdominal or pelvic malignancies, often leading to chronic gastrointestinal symptoms and impaired quality of life. Current treatments are mainly symptomatic and lack durable efficacy. Washed microbiota transplantation (WMT) has shown short-term benefits in RE, but the long-term effectiveness and optimal repeated-treatment strategy remain unclear. This study aimed to evaluate the long-term efficacy, treatment patterns, and safety of repeated WMT in patients with RE.Methods This prospective, observational study included patients with RE who received WMT at the Second Affiliated Hospital of Nanjing Medical University between March 2017 and June 2025 ( IDDF2026-ABS-0210 Figure 1. Flowchart of the study design). Disease severity and specific gastrointestinal symptoms were assessed using the Radiation Therapy Oncology Group (RTOG) score and the Common Terminology Criteria for Adverse Events (CTCAE). Clinical response was defined as a ≥1-grade decrease in RTOG score, and clinical remission as RTOG grade 0. Patients were evaluated at baseline and 8 weeks after each WMT course. Treatment-related adverse events were recorded throughout follow-up.Results A total of 63 patients were analyzed with a median follow-up of 36.3 months. The median duration of maintained response after the initial WMT was 83 days ( IDDF2026-ABS-0210 Figure 2. Duration of clinical response following initial WMT). More than half of the patients received ≥2 WMT courses, most commonly at approximately 3-month intervals. RTOG grades and total CTCAE scores significantly decreased after the first three WMT courses (all P < 0.05) (IDDF2026-ABS-0210 Figure 3). Overall, repeated WMT produced cumulative clinical benefit, with significant reductions in diarrhea, hematochezia, abdominal pain, abdominal distension, and fecal incontinence. After the final treatment, 31.7% of patients achieved clinical remission (IDDF2026-ABS-0210 Figure 4. Cumulative therapeutic effect of repeated treatment cycles). Multivariate analysis showed that a lower baseline RTOG grade was associated with a higher remission probability. Among 356 WMT procedures, only three mild adverse events occurred, all resolving spontaneously without intervention.Conclusions Repeated WMT is a safe and effective long-term management strategy for RE. Clinical benefits induced by a single WMT typically last about three months, and repeated WMT treatment at similar intervals may help maintain symptom control and improve cumulative outcomes.Abstract IDDF2026-ABS-0210 Figure 1Abstract IDDF2026-ABS-0210 Figure 2Abstract IDDF2026-ABS-0210 Figure 3Abstract IDDF2026-ABS-0210 Figure 4