Laser Energy Application in Endoscopic Kidney-Sparing Surgery for Upper Tract Urothelial Carcinoma: A Systematic Review of Oncological Outcomes and Surgical Complications

<b>Background:</b> Endoscopic kidney-sparing surgery (eKSS) is increasingly adopted for the management of selected patients with upper tract urothelial carcinoma (UTUC). Laser energy is central to tumor ablation during eKSS; however, multiple laser platforms with distinct physical and thermal properties are currently available, and their comparative oncological and safety profiles remain poorly defined. This systematic review aims to summarize the available evidence on oncological outcomes and perioperative complications associated with laser-based endoscopic treatment of UTUC and to explore potential differences according to laser technology. <b>Methods:</b> A systematic literature search identified 25 eligible studies published between 1997 and 2024, including 1344 patients treated with laser-assisted eKSS. All included studies were non-randomized, predominantly retrospective, and characterized by moderate-to-serious risk of bias. Holmium:YAG, Thulium:YAG (thu:YAG, continuous-wave and pulsed), thulium fiber laser (TFL), Neodimio:YAG (Nd:YAG), diode lasers, and combination platforms were reported. <b>Results:</b> Ipsilateral upper tract recurrence was common across all laser categories, with weighted proportions ranging approximately from 27% to 52% and substantial inter-study heterogeneity. Progression and conversion to radical nephroureterectomy (RNU) were relatively infrequent overall, with numerically weighted proportions observed in thu:YAG-based cohorts. Major complications (Clavien-Dindo ≥ III) were rare across all laser technologies, although a trend toward a higher weighted proportions was observed in Ho:YAG- and Nd:YAG-based series. Minor complications were more frequently reported and highly heterogeneous. <b>Conclusions:</b> Available evidence supporting laser selection in endoscopic kidney-sparing management of UTUC is limited and largely descriptive. Thulium:YAG and TFL platforms seem to demonstrate encouraging trends toward lower progression and conversion to-radical-nephroureterectomy rates; however, these findings are derived from heterogeneous, non-comparative studies with limited follow-up. No standard laser platform can currently be recommended over others based on existing data. Prospective, comparative, and methodologically robust studies are required to determine whether laser technologies confer clinically meaningful advantages in oncological control or safety for UTUC treated with eKSS.