This study was designed as a randomized controlled trial (RCT). The subjects who were scheduled RARP were recruited in this study from 2017 to 2019. Exclusion criteria were serious psychiatric, neurological diseases, and/or lower urinary tract infection. Sample size was calculated based on the previous RCT that reported 24-hour pad weight at 3 months after radical prostatectomy as primary endpoint [1]. The sample size was set at 27 participants per group to provide a power of 80% and a significance level of 5% for detecting the difference between groups. A final sample size was set at 30, which considered 3 participants as dropouts in each group. We randomly assigned men to receive either supervised PFMT or control group. This study was approved by the Ethics Committee in our institution. All participants provided written informed consent prior to participation. The current study involves the utilization of existing data from our previous study, “The effect of supervised pelvic floor muscle training on pelvic floor muscle function for the patients with UI after robot-assisted laparoscopic radical prostatectomy - A Randomised Controlled Trial -” which was accepted in International Continence Society 2020. The primary endpoint determined 24-hour pad weight (g) at 3 months after RARP. Also, we defined urinary continence as no pad use in the present study. PFM function such as resting anorectal pressure, maximum anorectical squeeze pressure, endurance, average, gradient, and area under curve (AUC) were included. Regarding PFM function, a manometer with anal sensor (PeritronTM cat 9300A; Laborie, Canada) was utilized for quantitative PFM assessment [2]. Maximal anorectal squeeze pressure is the peak value of anorectal squeeze pressure during contraction of the PFM. Duration is measured when the pressure reaches above 5 cm H2O. Average means area under the curve of anorectal squeeze pressure divided by contraction duration. Gradient is the peak value of anorectal squeeze pressure divided by the time taken to reach the maximum. Area under curve is anorectal squeeze pressure sampled 10 times per second, and divided by 10, multiplied by duration time. These outcomes were assessed before RARP, 7 days, 1, 3, 6, 12 months after RARP. The subjects in supervised PFMT group attended one-to-one PFMT session 3 times preoperatively, plus 7 days, 1, 3, 6, 12 months after RARP in total 8 times. In each session, subjects in supervised group were provided one-to-one session with a physiotherapist. Supervised group received verbal information about pelvic floor anatomy and function using an anatomical male pelvic model. They were taught isolated contraction of PFM without contracting the other muscles, including the outer abdominal muscles, and muscles of the hip joint with verbal instruction and palpation of PFM. Home-based PFMT was performed throughout this study. The subjects in control group were given only a leaflet about PFMT and lifestyle advice as daily care in our hospital.
In order to clarify the factors affecting the presence or absence of UI in 12 months, logistic regression analysis (forced input method) was performed. The dependent variable was the presence or absence of UI in 12 months, and the independent variables included the presence or absence of PFMT, body mass index (BMI), age, maximum anorectical squeeze pressure, endurance, and AUC. The significance level was set at p<0.05.