Long-term follow-up of patients undergoing adipose-derived adult stem cell administration to treat complex perianal fistulas

In patients with perianal fistulas, administration of adult stem cells (ASCs) derived from liposuction samples has proved a promising technique in a preceding phase II trial. We aimed to extend follow-up of these patients with this retrospective study. Patients who had received at least one dose of treatment (ASCs plus fibrin glue or fibrin glue alone) were included. Adverse events notified since the end of the phase II study were recorded. Clinical and magnetic resonance imaging (MRI) criteria were used to determine whether recurrence of the healed fistula had occurred. Data were available for 21 out of 24 patients treated with ASCs plus fibrin glue and 13 out of 25 patients treated with fibrin glue in the phase II study. Follow-up lasted a mean of 38.0 and 42.6 months, respectively. Two adverse events unrelated to the original treatment were reported, one in each group. There were no reports of anal incontinence associated with the procedure. Of the 12 patients treated with ASCs plus fibrin glue who were included in the retrospective follow-up in the complete closure group, only 7 remained free of recurrence. MRI was done in 31 patients. No relationship was detected between MRI results and the clinical fistula status, independent of the treatment received. Long-term follow-up reaffirmed the very good safety profile of the treatment. Nevertheless, a low proportion of the stem cell-treated patients with closure after the procedure remained free of recurrence after more than 3 years of follow-up.