Sentinel Lymph Node Mapping of Invasive Urinary Bladder Cancer in Animal Models Using Invisible Light

Abstract

ObjectivesWith conventional methodology, sentinel lymph node (SLN) mapping of invasive urinary bladder cancer is technically challenging. This study was performed to determine the utility of invisible, near-infrared fluorescent (NIRF) light for patient-specific SLN mapping, in real time under complete image guidance. MethodsLymphatic tracers, injection volume, NIRF excitation fluence rate, light collection of emitted fluorescence, and degree of bladder distension were systematically optimized in normal dogs and pigs. SLN mapping was then performed in pet dogs with naturally occurring invasive transitional cell carcinoma (InvTCC) of the urinary bladder, which closely mimics the human disease. ResultsNIRF albumin (hydrodynamic diameter [HD], 7.4nm) and NIRF quantum dots (15–20nm HD) injected into the bladder wall resulted in identification of draining lymph nodes (LNs) in under 3min. In both species, considerable variability in the lymphatic drainage was observed among individuals. Optimal SLN mapping was achieved with the use of superficial, serosal injection of NIRF tracer, with the bladder distended to an intraluminal pressure of 20–40cm H2O. In dogs with InvTCC, NIRF tracers identified SLNs that were confirmed histologically to harbor metastases. ConclusionsThe use of invisible NIRF light permits real-time, patient-specific identification of SLNs that drain bladder cancer. Intraluminal bladder pressure is a key parameter that needs to be controlled for optimal results.