Factors Associated With Efficacy of Percutaneous Tibial Nerve Stimulation for Fecal Incontinence, Based on Post-Hoc Analysis of Data From a Randomized Trial

BACKGROUND & AIMS: A recent randomized, multi-center, phase 3 trial, performed in the United Kingdom (Control of Fecal Incontinence using Distal Neuromodulation Trial), demonstrated no significant clinical benefit of percutaneous tibial nerve stimulation (PTNS) compared to sham stimulation in patients with fecal incontinence (FI). However, this study did not analyze predictors of response. We used data from this trial to identify factors that predict the efficacy of PTNS in adults with FI. METHODS: The study population comprised 205 patients from the CONtrol of Fecal Incontinence using Distal NeuromodulaTion Trial. The primary outcome was a binary indicator of success (>= 50% reduction in weekly FI episodes after 12 weeks of treatment) or failure, as per the original trial characteristics including baseline FI symptom type, defecatory urgency, and co-existent symptoms of baseline liquid stool consistency and obstructive defecation (OD) were defined a priori. Univariable and multivariable analyses were performed to explore these factors as predictors of response to PTNS and sham. RESULTS: In both univariable and multivariable analysis, the presence of OD symptoms negatively predicted outcome in patients who received PTNS (OR, 0.38; 95% CI, 0.16-0.91; P = .029), and positively predicted sham response (OR, 3.45; 95% CI, 1.31-9.21; P = .012). No other tested variable affected outcome. Re-analysis of the primary outcome excluding patients with OD symptoms (n = 112) resulted in a significant clinical effect of PTNS compared to sham (48.9% vs 18.2% response, P = .002; multivariable OR, 4.71; 95% CI, 1.71-12.93; P = .003). CONCLUSIONS: Concomitant OD symptoms negatively affected the clinical outcome of PTNS vs sham in a major randomized controlled trial. Future appropriately designed studies could further explore this observation with potential for future stratified patient selection.