Clinical efficacy of subsensory sacral neuromodulation in adults with faecal incontinence: The SUBSoNIC crossover randomised controlled trial and cohort follow‐up study

AIM: Sacral neuromodulation (SNM) is considered the first-line surgical treatment in adults with refractory faecal incontinence (FI). However, its clinical efficacy has not been rigorously tested in a trial setting. METHOD: Randomised, multicentre, double-blind crossover trial (two 16-week periods) of active stimulation versus sham, and open-label follow-up to 58 weeks. PARTICIPANTS: adults aged 18-80 with refractory FI. INTERVENTIONS: Active: subsensory sacral nerve stimulation with an implanted pulse generator; Sham: identical implant but turned off. PRIMARY OUTCOME: FI episodes per week (paper bowel diary) during final 4 weeks of crossover periods (allowing 12 weeks' washout). Randomised allocation (1:1) to arm 1 (SNM/sham) or arm 2 (sham/SNM). BLINDING: participants, surgeons, assessors; tamper-proof tape-masked stimulation settings. SAMPLE SIZE: 80 patients to detect a 30% reduction in episodes. Groups compared using a paired t-test, and treatment effects summarised by mean differences. RESULTS: Trial delivery was severely affected by COVID-19. Thirty-nine patients of 220 screened (arm 1: N = 17; arm 2: N = 22) were recruited at 10 sites (February 2018-July 2022), of whom only 16 (arm 1: N = 9; arm 2: N = 7) had complete primary outcome data. Of the 39, 19 completed follow-up to 58 weeks. SNM conferred a non-significant reduction in mean FI episodes per week compared to sham (-0.795 95% CI: -1.5 to 0.0, p = 0.06). Improvements were observed in FI symptoms at 58 weeks compared to baseline (FI episodes per week: 3.2 SD 3.3 vs. 6.2 SD 5.9). CONCLUSIONS: The SUBSoNIC trial failed to find conclusive evidence of the experimental efficacy of SNM. Further demonstration of experimental efficacy remains important as SNM is a high-cost and invasive therapy.