Endoscopic Treatment of Upper Tract Urothelial Carcinoma: Challenging the Definition of the Maximal Lesion Size for Safe Ablation

Introduction: With advances in endoscopic treatment of upper tract urothelial carcinoma (UTUC) lesions, the recommended upper limit of lesion size amenable to laser ablation was set to 2 cm. However, this limit is based on expert opinion only, and debate still exists regarding this definition. Objective: To determine the maximal size of the tissue, for which total endoscopic ablation with laser energy is achievable, from a laser performance perspective. Materials and Methods: Simulating endoscopic surgery conditions, renal tissue blocks from pork kidneys in growing size from 1 cm3 to 3 cm3 were totally ablated with Ho:YAG laser (1 J, 10 Hz). The time to ablation was recorded for each tissue mass. Following the ablation, each sample was inspected microscopically by an expert pathologist to determine the extent to which the tissue was destroyed. Results: Time to ablation ranged from 16.4 min for a 1 cm3 mass, to 69.7 min for a 3 cm3 mass. Histologic evaluation after laser ablation showed that ablation was achieved in all tissue masses, and no “unaffected” tissue was present, even for lesions with a size of 3 cm3. Conclusions: This study showed that laser ablation can be achieved for tumor lesions up to a size of 3 cm3. The results of this study can contribute to the debate regarding the limits of endoscopic management of UTUC lesions and strengthen the recommended upper limit of 2 cm3 for endoscopic treatment of tumor lesions.