Studies demonstrated the significance of membranous urethral length (MUL) as a predictor of continence following robot-assisted radical prostatectomy (RARP). There are other magnetic resonance imaging (MRI) parameters that might be linked to continence outcome.
To evaluate the association between preoperative urethral parameters on MRI and continence outcome, to estimate the risk of incontinence using different cut-off values, and to assess interobserver variability in measuring urethral parameters.
Patients with localised prostate cancer who underwent RARP were retrospectively reviewed. Baseline patient characteristics, perioperative, and pathological outcomes were assessed. Continence was defined as no pad or a safety pad with <2g/24h pad weight.
Several MRI variables were measured by a uroradiologist, a uro-oncology fellow, and a urologist. Binary logistic regression analyses were performed to identify predictors of incontinence. Interclass correlation was used to evaluate interobserver variability.
A total of 190 patients met the study inclusion criteria. The mean MUL was 14.6mm. Age and MUL were significantly associated with incontinence outcome. The area under the receiver operating characteristic curve for continence based on MUL was 0.78 at 12 mo. The risk of incontinence in patients with MUL of <10mm was 27.8% (13.8% and 39.1% for patients aged <65 and >65 yr respectively). Conversely, the risk of incontinence with MUL >15mm was 2.7% (1.5% and 4.5% for patients aged <65 and >65 yr, respectively). The concordance rate between different observers was 89% for coronal MUL, but 77%, 74%, and 62% for sagittal MUL, membranous urethral thickness, and intraprostatic urethral length, respectively.
This study confirmed the significance of MUL for the continence outcome following RARP. There was also excellent consistency in measuring MUL values between different observers.
Although further studies would be required to verify our findings, we support the significance of membranous urethral length in predicting the risk of incontinence and the need to incorporate it as part of preoperative assessment and counselling. This can reliably be measured by urologists and can further facilitate a patient-tailored approach to radical treatment of prostate cancer.
European urology focus. 2019 Jan 25 [Epub ahead of print]
Lawrence H C Kim, Amit Patel, Netty Kinsella, Mansour T A Sharabiani, Derfel Ap Dafydd, Declan Cahill
Royal Marsden Hospital, London, UK. Electronic address: ., Royal Marsden Hospital, London, UK.