Assessing the Feasibility and Accuracy of High-resolution Microultrasound Imaging for Bladder Cancer Detection and Staging

Abstract

Background: Magnetic resonance imaging (MRI) has been proposed as a staging tool for bladder cancer (BC), but its use has been limited by its high costs and limited availability. Microultrasound (mUS) is a novel technology capable of providing high-resolution images of the prostate.

Objective: To test the feasibility of high-resolution mUS in patients diagnosed with BC and its ability to differentiate between non-muscle-invasive BC (NMIBC) and muscle-invasive BC (MIBC).

Design, setting, and participants: This is an observational prospective study performed in 23 patients with a diagnosis of primary BC scheduled for an endoscopic treatment.

Surgical procedure: Micro-US was performed before transurethral resection of bladder tumor using the ExactVu system with an EV29L 29-MHz side-fire transducer (Exact Imaging, Markham, Canada).

Measurements: The endpoints were to test the feasibility, describe the normal bladder wall anatomy, identify the lesions, and compare the mUS findings with the histopathological results.

Results and limitations: Micro-US was accurate in differentiating the three layers of the bladder wall in all cases. Bladder cancers were clearly identified as heterogeneous structures protruding from the normal bladder wall. In 14 cases the lesions appeared confined to the lamina propria, and in all cases NMIBC was confirmed by the final pathological report. In the other patients, the lesions seemed to extend into the muscular layer, but MIBC was confirmed in five out of seven cases (71.4%) from the pathologist. The small sample size was the main limitation of the current study.

Conclusions: Our findings showed that mUS is able to differentiate the bladder wall layers and identify the bladder cancer stage. Further studies with a larger population and imaging correlation with MRI are warranted before its introduction in clinical practice.

Patient summary: In this report, a new imaging technique was tested for the characterization of bladder cancer. Microultrasound appears to be feasible and capable of discriminating between superficial and invasive tumors.

Keywords: Bladder cancer; High-resolution ultrasound; Microultrasound; Muscle-invasive bladder cancer; Non-muscle-invasive bladder cancer; Staging.