The clinical efficacy of stem cell therapy for complex perianal fistulas: a meta-analysis.

BACKGROUND: Treatment of complex anal fistulas remains difficult. However, treatment with stem cells has had an encouraging success rate when applied to complex perianal fistulas. We systematically reviewed the current evidence through meta-analysis. METHODS: We performed an electronic literature search on PubMed, Embase, and the Cochrane Library and identified studies (published between January 1946 and August 2017) that used stem cells to treat patients with complex perianal fistula. Each paper was evaluated for treatment success rate, target patients, types of stem cells used, number of cells used, and criteria for complete healing. Potential publication bias was assessed via visual inspection of a funnel plot and Orwin's fail-safe N. Out of 171 papers, 16 were included in the meta-analysis. RESULTS: The overall healing rate of stem cell injection therapy for patients with complex perianal fistulas was 62.8% (95% CI 53.5-71.2, I2 = 54.05%), whereas those for patients with Crohn's perianal fistulas alone and complex anal fistulas not associated with Crohn's disease were 64.1% and 61.5% (p = 0.840), respectively. Healing rates for autologous and allogenic stem cell treatment were 69.4% and 50.7% (p = 0.020), respectively. Four comparative studies out of 16 studies were analyzed separately. Stem cell therapy increased the healing rate compared to the control groups (OR 0.379, 95% CI 0.152-0.947). CONCLUSIONS: Stem cell therapy is a good treatment option for complex perianal fistulas, which cannot be healed by conventional operative procedures. However, further research for additional supportive evidence, such as a large-scale randomized controlled trial, is required.