Single-incision mini-slings versus standard synthetic mid-urethral slings for surgical treatment of stress urinary incontinence in women: The SIMS RCT

BACKGROUND: Stress 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.

OBJECTIVE: The 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.

DESIGN: This was a pragmatic non-inferiority randomised controlled trial. Allocation was by remote web-based randomisation (1 : 1 ratio).

SETTING: The trial was set in 21 UK hospitals.

PARTICIPANTS: Participants were women aged ≥ 18 years with predominant stress urinary incontinence, undergoing a mid-urethral sling procedure.

INTERVENTIONS: Single-incision mini-slings, compared with standard mid-urethral slings.

MAIN OUTCOME MEASURES: The 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.

RESULTS: A 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; p non-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; p non-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.

LIMITATIONS: Follow-up data beyond 3 years post randomisation are not available to inform longer-term safety and cost-effectiveness.

CONCLUSIONS: Single-incision mini-slings were non-inferior to standard mid-urethral slings in patient-reported success rates at up to 3 years' follow-up.

FUTURE WORK: Success rates, adverse events, retreatment rates, symptoms, and quality-of-life scores at 10 years' follow-up will help inform long-term effectiveness.

TRIAL REGISTRATION: This trial was registered as ISRCTN93264234.

FUNDING: This project was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 26, No. 47. See the NIHR Journals Library website for further project information.