Overactive bladder (OAB) is a chronic condition that affects up to 100 million people in Europe and North America (1). Sacral Neuromodulation (SNM) is an established therapy in patients with refractory overactive bladder (OAB). Historically, SNM was delivered using a primary-cell, non-rechargeable system with a device lifespan of approximately 4.4 years (2). Using a non-rechargeable system requires several replacement surgeries over time and exposes patients to increased surgical risks and healthcare costs.  Use of a long-lived device could significantly reduce patient surgical risks and healthcare costs (3). 

The Axonics® miniaturized, rechargeable Sacral Neuromodulation (r-SNMTM) system is designed and qualified to last for at least 15 years in the body. This system has regulatory approval in Europe (CE mark), Canada, and Australia and is currently under review for PMA approval from the US FDA. The RELAX-OAB study was a post-market, prospective clinical follow-up study designed to confirm the safety and efficacy of the Axonics r-SNM System. Two years results are presented here.

The RELAX-OAB study treated 51 OAB patients across 7 Western European centers. Participants were implanted with the tined lead and the Axonics implantable neurostimulator (INS) in a single, non-staged procedure, without requiring prior testing with an external trial system. Fluoroscopic guidance was used to implant the tined lead along the S3 or S4 sacral nerve root.  Voiding diaries (3-day) were completed at baseline and at post-implant follow-up visits. Data on participant quality of life was collected using the ICIQ-OABqol validated questionnaire. Participants reported data included satisfaction with treatment, ease of recharging and acceptability of recharging duration. To be comparable with the clinical literature for two-stage SNM treatment, up to the first month post-implant was considered as the “Test Period”, and participants were deemed to be Test Responders or Test Failures based on clinical outcomes at 2-week or 1-month visits. Responders were identified as participants that experienced ≥50% reduction in voids and/or urinary incontinence episodes compared to baseline or a reduction in voids to less than 8 per day. All participants were followed for 2 years regardless of their Test Period outcome. Data analyzed per-protocol is presented.

A total of 38 females and 13 males, average age of 51 years old (21-77 years), were implanted with the Axonics r-SNM System. At baseline participants averaged (standard error) 14.6 ± 1.1 voids per day and 9.6 ± 0.8 urinary incontinence episodes per day. Thirty-four of 51 (71%) participants were Test Responders at 1-month post-implant. Data from a total of 40 participants was available at 2 years, including 76% of the Test Responders.  

At 2 years, 90% of the Test Responders continued to be Therapy Responders. Baseline voids per day of 14.3 ± 1.1 were reduced to 7.2 ± 0.4 at 2 years in Test Responders (p<0.001, two-sided paired t-test, Figure 1). Baseline urinary incontinence episodes of 8.3 ± 0.8 per day were reduced to 1.7 ± 0.5 per day at 2 years in Test Responders (p<0.001, two-sided paired t-test, Figure 1). Seventy-six percent of the Test Responders had ≥70% reduction in urinary incontinence episodes and 28% were dry.  

Test Responders experienced clinically meaningful improvements in quality of life at 2 years based on an average improvement of 26.3 points in the ICIQ-OABqol compared to baseline (Figure 2). Improvements on all quality of life subscales were statistically significant and clinically significant (above the minimally important difference of 10 points).

Participant satisfaction results were consistent with QoL results. Ninety-three percent of the Test Responders were satisfied with their r-SNM therapy. Eighty-six percent of all implanted participants reported the charging frequency and duration to be acceptable.  

No serious device-related adverse events have been reported. Five of fifty-one (5 of 51) or 9.8% of participants have been explanted. Device explant occurred in one participant due to a post-operative wound infection, in three participants due to lack of efficacy, and in one participant due to need for MRI before full body MRI approval was available in this region. No adverse events were reported related to device recharging.

The results confirm the long-term safety and sustained efficacy of the rechargeable Axonics r-SNM System at 2 years. A rechargeable SNM system is expected to provide significant cost-effectiveness and long-lived therapeutic benefits compared to existing non-rechargeable systems.

Participants implanted with the Axonics r-SNM System have received clinically significant improvements in their symptoms and quality of life at 2 years post-implant. Participants reported satisfaction with r-SNM therapy and an acceptable recharging experience.

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