Percutaneous Nerve Evaluation Trial Time

Sacral neuromodulation (SNM) is a minimally invasive procedure that provides low-amplitude electrical stimulation to the S3 nerve root to improve micturition and defecation. It is FDA-approved for the treatment of urgency urinary incontinence (UUI) refractory to behavioral modifications and/or oral medication. The efficacy of SNM for the treatment of UUI is well studied and currently, there are two manufacturers of SNM devices within the United States: Medtronic and Axonics. Both offer rechargeable and non-rechargeable devices.

Patients who elect to proceed with SNM undergo a trial phase to determine therapeutic response prior to placement of a permanent implantable pulse generator (IPG). A trial phase can be performed in two ways: a percutaneous nerve evaluation (PNE) or staged implantation. PNE involves the placement of a temporary wire connected to an electrode using external stimulation. It is performed in the office using local anesthesia. If the patient displays adequate improvement in symptoms (defined as >50% improvement of symptoms from baseline), a permanent lead and subcutaneous IPG are implanted in the operating room. The staged approach involves two separate procedures performed in the operating room: stage I and stage II. Stage I is the clinical trial of the permanent lead with electrodes using external stimulation. Following adequate response, stage II is performed and involves the IPG placement.

PNE offers significant advantages compared to a staged implantation. A PNE is performed in the office under local anesthesia mitigating the anesthetic risk and number of operating room visits. PNE is also suspected to be cost-effective given it is performed in the office with minimal medical equipment; however, this has not been well studied. Full implantation rates are 40-50% following PNE versus 70-90% in women who undergo a staged approach. The lower rate of progression to full implantation with PNE can be attributed to several factors including lead migration. The monopolar PNE lead does not have a self-retaining component like the quadripolar tined lead used during a stage approach. Newer registry data suggest up to 90% of PNE trials lead to full implantation. Authors hypothesize the improved full implantation rates in the newer studies may be secondary to shorter trial times and improved anatomic knowledge.

The trial phase is the most valuable tool to predict therapeutic success of SNM for women with UUI. Several large, multicenter trials support that PNE and staged trial can predict patients who are likely to respond to SNM therapy and experience long term benefits. Literature is limited regarding recommended length of time for the trial phase. The International Continence Society best practice statement for use of SNM currently recommends 7-day trial for women with UUI. However, one study reported high sensitivity and specificity of PNE with a trial time of 3-5 days. This cross-sectional study was limited to a single institution and included patients with nonobstructive urinary retention.

Given the risk of lead migration with PNE, the investigators hypothesize that shortening the trial phase to 3 days will not decrease the proportion of patients who progress onto full SNM implantation. The investigators believe that shortening the window to capture therapeutic response will have several important patient benefits and reduce the chance of lead migration without adversely impacting outcomes. Therefore, the investigators aim to perform a multi-center, randomized trial to determine if a 3-day PNE trial is not inferior to a 7-day PNE trial with respect to rates of progression to full SNM implantation.

The investigators plan to perform a multi-center, randomized, non-inferiority trial of patients receiving SNM for UUI or urgency-frequency syndrome (UF) who elect to undergo a PNE. Informed consent will be obtained for participants who meet eligibility criteria. Participants will be computer randomized in a 1:1 fashion to either a 3 or 7-day PNE trial on the day of PNE (to minimize bias and drop out). Permuted blocks will be utilized with a fixed block size stratified by age (<65 versus >65 years old) and study site. Decision to stratify by age is based on the association between advancing age and decreased SNM response. Patients must have at least 5 episodes of UUI or at least 8 voids per day for 2 days on a 3-day bladder diary to be included. Demographic and symptom data will be collected at participants baseline visit including a 3-day bladder diary and validated patient reported outcome measures for urinary symptoms and quality of life (Urinary Distress Inventory, Lower Urinary Tract Dysfunction Research Network Symptom Index-10, Incontinence Impact Questionnaire). At the PNE visit and PNE removal, clinical information will be recorded, and patient reported outcome measures will be repeated (including Patient Global Impression of Improvement). Patients who have an adequate response to PNE placement (>50% improvement in UUI/UF symptoms determined by 3-day bladder diary) will progress to full SNM implantation.

Assuming a significance level of 5% and 80% rate of progression to full implantation in each arm with a noninferiority margin of 15 percentage points, the investigators calculate that 88 women would need to enroll in each study arm to have 80% power for determining whether the results in the 3-day PNE trial arm are noninferior to those in the 7-day trial arm. The investigators propose a 15% noninferiority margin on the basis of clinical judgement that this is a reasonable tradeoff between a decrease in progression to full or stage implantation and the possibility of shortening the PNE trial period. Assuming a 10% dropout rate, a total sample of 193 women will be required. Non-inferiority will be declared if the upper bound of the 95% confidence interval for the rate of progression to full implantation between groups is less than 15%. To minimize bias toward noninferiority, only women treated per protocol will be considered in the primary outcome analysis.

De-identified data will be collected at each site in a REDCap database then transferred to an SPSS database (IBM SPSS Statistics for Macintosh, Version 22.0. Armonk, NY: IBM Corp) for statistical analysis. Secondary outcomes will be assessed using intent to treat analyses.

Comparative statistics for patient demographics and clinical outcomes will be performed between the two cohorts utilizing chi-square, t-test, and Wilcoxon test as appropriate for continuous and categorical variables. Logistic regression models will be used to evaluate the association between factors and rate of full SNM implantation following PNE. Multivariate logistic regression to control for potential cofounding variables.

The investigators estimate being able to recruit 3 women undergoing PNE each month during the study period from the investigator's site or 36 participants in 1-year. Given the standard of care is a 7-day PNE, the investigators anticipate patients will be eager for the option to be randomized to a less onerous test period. In addition, the only patient burden (beyond standard of care) is completion of a series of validated questionnaires, which the investigators estimate will take 15 minutes at both time points. There are currently two SNM device manufacturers (Medtronic and Axonics) as well as a national-reported increased in SNM implantation procedures over the past decade.15 While there are no comparative date between these devices, the investigators think both can be included in this trial to increase generalizability.