Sequencing and Combination of Mirabegron and TTNS in Overactive Bladder Syndrome: a Multicenter, Randomized, Open-label, Crossover Trial

Research question:

A wealth of existing research has established the independent effectiveness of mirabegron and neuromodulation in the treatment of overactive bladder syndrome. Optimizing the use of these effective and well-tolerated treatment modalities is an important clinical goal and warrants further research. The primary aim of this trial is to answer the questions: how does varying the treatment sequence involving mirabegron and transcutaneous tibial nerve stimulation (TTNS) affect efficacy and patient acceptance and what is the second-line efficacy of either treatment modality?

Primary objective:

To evaluate improvement in storage symptoms, as measured by changes in Overactive Bladder Symptom Score (OABSS), International Prostate Symptom Score (IPSS) and parameters of voiding diary, in overactive bladder (OAB) patients receiving mirabegron or TTNS as first-line therapy when crossed over to second-line therapy with the opposite treatment modality

Secondary objectives:

To evaluate improvement in symptoms, as measured by changes in OABSS, IPSS and parameters of voiding diary, on first-line therapy with mirabegron or TTNS followed by combination multi-modal therapy To evaluate the effect of multi-modal treatment approach on patient's perception of treatment satisfaction and symptom control To evaluate urodynamic profiles of patients treated with multi-modal approach

Study design: Prospective, randomized, multicenter, open-label, cross-over trial Treatment sequence: randomized with 1:1 ratio to either Sequence A or Sequence B

Sequence A: mirabegron 50mg monotherapy x 8 weeks -\> multi-modal combination treatment x 4 weeks -\> TTNS monotherapy x 8 weeks Sequence B: TTNS monotherapy x 8 weeks -\> multi-modal combination treatment x 4 weeks -\> mirabegron 50mg monotherapy x 8 weeks

Patient population: adults ≥ 20 years who have experienced symptoms of OAB, as defined by International Continence Society (ICS) diagnostic criteria, for at least 3 months

Sample size: approximately 180 patients

Eligibility Criteria:
Inclusion Criteria:

* Adult OAB patients ≥20 years
* Diagnosed with moderate to severe OAB (with or without urgency incontinence) based on OABSS \>5 and clinical assessment, with UUI-predominant presentation, for at least 3 months
* Able to receive TTNS and accommodate treatment logistics (30 min per on-site session, twice weekly)
* Provided informed consent to participate in the study

Exclusion Criteria:

* Neurologic conditions associated with OAB symptoms
* History of stress urinary incontinence
* Use of intravesical onabotulinumoxinA within recent 6 months
* Postvoid residual urine volume (PVR) ≥ 100mL
* Evidence of active urinary tract infection or urinary tract stone at screening
* Genitourinary tract operation during the 3-month period prior to baseline
* Confirmed or suspected genitourinary tract or pelvic malignancy
* History of uncontrolled hypertension (systolic \>160 mmHg and/or diastolic \>110 mmHg)
* History of intolerance to mirabegron
* Patients with pacemakers or implantable defibrillators
* Patients prone to excessive bleeding
* Patients with nerve damage that could impact percutaneous tibial nerve or pelvic floor function
* Patients who are pregnant or planning to become pregnant during the duration of treatment
* History of medical conditions or presence of patient factors that, in the judgement of the investigator, would preclude adherence to study protocol