Optical Diagnostics for Upper Urinary Tract Urothelial Cancer: Technology, Thresholds, and Clinical Applications

Purpose: Developments in optical diagnostics have potential for less invasive diagnosis of upper urinary tract urothelial carcinoma (UUT-UC). This systematic review provides an overview of technology, applications, and limitations of recently developed optical diagnostics in the upper urinary tract and outlines their potential for future clinical applications. In addition, current evidence was evaluated. Literature Search: A PubMed literature search was performed and articles on narrow band imaging (NBI), photodynamic diagnosis (PDD), Storz professional imaging enhancement system (SPIES), optical coherence tomography (OCT), and confocal laser endomicroscopy (CLE) regarding UUT-UC were reviewed for data extraction. Study quality was reviewed according to Quality Assessment of Diagnostic Accuracy Studies and Innovation, Development, Exploration, Assessment, and Long-term follow-up (IDEAL) standards. Results: Four articles available for quality assessment, demonstrated high level of evidence, but low level of IDEAL stage. NBI and SPIES enhance contrast of mucosal surface and vascular structures, improving tumor detection rate. A first in vivo study showed promising results. PDD uses fluorescence to improve tumor detection rate. However, due to the acute angle of the ureterorenoscopes there is an increased risk of false positives. OCT produces cross-sectional high-resolution images, providing information on tumor grade and stage. A pilot study showed promising diagnostic accuracy. CLE allows ultrahigh-resolution microscopy of tissue resulting in images of the cellular structure. CLE cannot be applied in vivo in the upper urinary tract yet, due to technical limitations. Conclusions: NBI, SPIES, and PDD aim at improving visualization of UUT-UC through contrast enhancement. OCT and CLE aim at providing real-time predictions of histopathological diagnosis. For all techniques, more research has to be conducted before these techniques can be implemented in the routine management of UUT-UC. All techniques might be of value in specific clinical scenarios and allow for integration, for example, OCT with NBI, and could therefore improve tumor detection and staging and help in selecting the optimal treatment for the individual patient.