Single-incision mini-slings versus standard synthetic mid-urethral slings for surgical treatment of stress urinary incontinence in women: The SIMS RCT
Authors: Abdel-Fattah Mohamed , Cooper David , Davidson Tracey , Kilonzo Mary , Boyers Dwayne , Bhal Kiron , McDonald Alison , Wardle Judith , N’Dow James , MacLennan Graeme , Norrie John 
Published: December 2022

BackgroundStress urinary incontinence is the most common type of urinary incontinence in premenopausal women. Until recently, synthetic mid-urethral slings (mesh/tape) were the standard surgical treatment, if conservative management failed. Adjustable anchored single-incision mini-slings are newer, use less mesh and may reduce perioperative morbidity, but it is unclear how their success rates and safety compare with those of standard tension-free mid-urethral slings.ObjectiveThe objective was to compare tension-free standard mid-urethral slings with adjustable anchored single-incision mini-slings among women with stress urinary incontinence requiring surgical intervention, in terms of patient-reported effectiveness, health-related quality of life, safety and cost-effectiveness.DesignThis was a pragmatic non-inferiority randomised controlled trial. Allocation was by remote web-based randomisation (1 : 1 ratio).SettingThe trial was set in 21 UK hospitals.ParticipantsParticipants were women aged ≥ 18 years with predominant stress urinary incontinence, undergoing a mid-urethral sling procedure.InterventionsSingle-incision mini-slings, compared with standard mid-urethral slings.Main outcome measuresThe primary outcome was patient-reported success rates on the Patient Global Impression of Improvement scale at 15 months post randomisation (≈ 1 year post surgery), with success defined as outcomes of ‘very much improved’ or ‘much improved’. The primary economic outcome was incremental cost per quality-adjusted life-year gained. Secondary outcomes were adverse events, impact on other urinary symptoms, quality of life and sexual function.ResultsA total of 600 participants were randomised. At 15 months post randomisation, adjustable anchored single-incision mini-slings were non-inferior to tension-free standard mid-urethral slings at the 10% margin for the primary outcome [single-incision mini-sling 79% (212/268) vs. standard mid-urethral sling 76% (189/250), risk difference 4.6, 95% confidence interval –2.7 to 11.8;pnon-inferiority < 0.001]. Similarly, at 3 years’ follow-up, patient-reported success rates in the single-incision mini-sling group were non-inferior to those of the standard mid-urethral sling group at the 10% margin [single-incision mini-sling 72% (177/246) vs. standard mid-urethral sling 67% (157/235), risk difference 5.7, 95% confidence interval –1.3 to 12.8;pnon-inferiority < 0.001]. Tape/mesh exposure rates were higher for single-incision mini-sling participants, with 3.3% (9/276) [compared with 1.9% (5/261) in the standard mid-urethral sling group] reporting tape exposure over the 3 years of follow-up. The rate of groin/thigh pain was slightly higher in the single-incision mini-sling group at 15 months [single-incision mini-sling 15% (41/276) vs. standard mid-urethral sling 12% (31/261), risk difference 3.0%, 95% confidence interval –1.1% to 7.1%]; however, by 3 years, the rate of pain was slightly higher among the standard mid-urethral sling participants [single-incision mini-sling 14% (39/276) vs. standard mid-urethral sling 15% (39/261), risk difference –0.8, 95% confidence interval –4.1 to 2.5]. At the 3-year follow-up, quality of life and sexual function outcomes were similar in both groups: for the International Consultation on Incontinence Questionnaire Lower Urinary Tract Symptoms Quality of Life, the mean difference in scores was –1.1 (95% confidence interval –3.1 to 0.8;p = 0.24), and for the Pelvic Organ Prolapse/Urinary Incontinence Sexual Questionnaire, International Urogynecological Association-Revised, it was 0 (95% confidence interval –0.1, 0.1;p = 0.92). However, more women in the single-incision mini-sling group reported dyspareunia [12% (17/145), compared with 4.8% (7/145) in the standard mid-urethral sling group, risk difference 7.0%, 95% confidence interval 1.9% to 12.1%]. The base-case economics results showed no difference in costs (–£6, 95% confidence interval –£228 to £208) or quality-adjusted life-years (0.005, 95% confidence interval -0.068 to 0.073) between the groups. There is a 56% probability that single-incision mini-slings will be considered cost-effective at the £20,000 willingness-to-pay threshold value for a quality-adjusted life-year.LimitationsFollow-up data beyond 3 years post randomisation are not available to inform longer-term safety and cost-effectiveness.ConclusionsSingle-incision mini-slings were non-inferior to standard mid-urethral slings in patient-reported success rates at up to 3 years’ follow-up.Future workSuccess rates, adverse events, retreatment rates, symptoms, and quality-of-life scores at 10 years’ follow-up will help inform long-term effectiveness.Trial registrationThis trial was registered as ISRCTN93264234.FundingThis project was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme and will be published in full inHealth Technology Assessment; Vol. 26, No. 47. See the NIHR Journals Library website for further project information.