P0868 Long term outcomes from UK mesenchymal stem cell therapy for perianal fistulising Crohn’s disease: a 5 Year follow up
Authors: Anand Mr E , Rea B , Iqbal N , Sayers A , Hart A , Lung P , Brown S , Tozer P 
Published: January 2025

Abstract

Background
Perianal fistulising Crohn’s disease (pfCD) is a debilitating and complex complication of Crohn’s disease that is challenging to manage and associated with poor long-term outcomes. Mesenchymal stem cell (MSC) therapy has emerged as a promising treatment option for medically refractory pfCD, but long-term data on efficacy and safety are limited. This study investigates the long-term outcomes of MSC therapy in patients with pfCD, focusing on clinical, radiological and patient-reported outcomes.

Methods
All patients treated with a single dose of MSC therapy at two tertiary referral centres in the UK were included in a prospectively maintained cohort and patients were followed up for 5 years. The primary outcomes were clinical and radiological response, assessed using the fistula drainage assessment, TOpClass consensus definitions of radiological improvement and healed fistulae, MRI-based activity indices and expert radiologists’ VAS (Visual Analogue Scale) score of disease severity. Secondary outcomes include the Perianal Disease Activity Index (PDAI) and the Vaizey incontinence score.

Results
The analysis included 24 patients (14 female, 10 male) with a mean age of 37. The median follow-up was 60 months (clinical assessments) and 54 months (radiological evaluations). At 5 years, 25% patients (6/24) had evidence of persisting clinical response, and 54.2% (13/24) were in clinical remission. Radiologically, 75% (18/24) of patients showed improvement in the first 12 months post-treatment, with 37.5% (9/24) maintaining long-term radiological improvement at 5 years. Four patients (16.7%) achieved complete radiological healing at 5 years. The Van Assche Index score improved post treatment (p = 0.042) and long-term (p = 0.019), in concordance with a reduction in the radiologists’ VAS severity score post – treatment (p = 0.009) and at 5 years (p = 0.043). Significant reductions in PDAI were observed from baseline to 18 months (p&lt; 0.001) and 5 years (p= 0.002). During the 5-year follow-up period, 58.3% (14 out of 24) of patients did not require additional surgery, and no adverse events or long-term continence impairment were observed (p = 0.582).

Conclusion
This study demonstrates that MSC therapy for pCD results in significant long-term clinical and radiological improvements, with clinical remission in half of patients at 5 years and a safety profile consistent with prior studies. Despite the clinical remission, at 5 years only a minority experienced sustained radiological healing (16.7%) according to the new and stringent TOpClass definition. These findings support the use of MSC therapy as an effective treatment for pfCD, with durable benefits in symptom control and quality of life.

References
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