Prospective Single-Center Study of SuperPulsed Thulium Fiber Laser in Retrograde Intrarenal Surgery: Initial Clinical Data

Abstract

<b><i>Introduction:</i></b> The objective of this study was to present our clinical experience of using the thulium fiber laser in retrograde intrarenal surgery (RIRS). <b><i>Methods:</i></b> A prospective clinical study performed after the IRB approval (Sechenov University, Russia). Patients with stones <30 mm were treated with SuperPulsed thulium fiber laser (SP TFL) (NTO IRE-Polus, Russia) through a 200-μm-diameter fiber. Stone size, density, the duration of the operation, and laser on time (LOT) were measured. Based on the surgeon’s feedback, retropulsion and intraoperative visibility were also assessed (Likert scale). Stone-free rates (SFRs) were assessed with a low-dose CT scan 90 days after the operation. <b><i>Results:</i></b> Between January 2018 and December 2019, 153 patients (mean age 54 ± 2.8 years) underwent RIRS with SP TFL (mean stone density 1,020 ± 382 HU). Median stone volume was 279.6 (139.4–615.8) mm<sup>3</sup>. Median LOT was 2.8 (IQR 1.6–6.6) min with median total energy for stone ablation 4.0 (IQR 2.1–7.17) kJ, median ablation speed was 1.7 (1.0–2.8) mm<sup>3</sup>/s, median ablation efficacy was 13.3 (7.3–20.9) J/mm<sup>3</sup>, and energy consumption was 170.3 (59.7–743.3) J/s. Overall, the SFR (at 3 months) was 89%. The overall complication rate was 8.4%. Retropulsion was present in 23 (15.1%) patients. Visibility was estimated as optimal in most patients, with poor visibility reported in only 13 (8.5%) patients. <b><i>Conclusion:</i></b> The SP TFL is a safe and efficient tool in lithotripsy, irrespective of the stone type and density. Retropulsion is minimal and visibility is maintained with SP TFL. Nonetheless, further clinical studies are needed to ensure optimal comparison with conventional holmium:YAG lithotripsy.

Thulium fiber laser in urology: physics made simple

“…Moreover, TFL allows to achieve a stone-free rate up to 92,5% in RIRS and PCNL [35,37]. Finally, the safety profile of TFL is comparable with conventional technologies and according to available data does not exceed Clavien-Dindo grade II [38] (Fig. 2a).…”

Retrograde intrarenal surgery: laser showdown (Ho:YAG vs thulium fiber laser)

“…In terms of complication, in the first clinical trial made in Europe [9], none of the complications were related to the TFL. Complications reported in other trials were mostly low and Clavien-Dindo grade I or II, none of them were associated with the use of a specific regimen [9,10,[16][17][18]. Thus, as Ho:YAG laser ELL, TFL can be safety performed in human beings and with little complications until now.…”

“…However, TFL has a peak power of 500 W that is constant and prolonged that makes the pulse width, even if low, a long one when faced to the Ho:YAG and can perform an efficient lithotripsy with this parameter [9,10]. Compared to the Ho:YAG laser, clinical trials made with the TFL have shown that the volume ablated by a single pulse emitted is at least two times higher for all stone types [9][10][11][12][13][14][15][16][17][18]. This means that, in terms of laser showdown, TFL overcomes the Ho:YAG laser in the ablation efficiency if we gather all the clinical trials published until now worldwide.…”

“…From the 5 clinical trials mentioned, only 3 had reported ablation speed and ablation efficiency, which at least two-times faster and up to two-times higher than the results in Ho:YAG RIRS [9,10,18]. SFR was also assessed and it goes from 78.9% [16], 89% [18], 92.5%, [10], up to 95% [17] in some clinical studies. These surprising results reflect what was mentioned before about ablation efficiency, ablation speed and retropulsion obtained with this new technology, that overcomes its predecessor Ho:YAG laser and showing that TFL can perform an efficient RIRS with at least the half of the LOT, when compared to the Ho:YAG laser and for a similar stone volume and density.…”

“…The median lithotripsy time for the standard Ho:YAG is around 68 min with a median laser-on time (LOT) of 84%, for patients undergoing RIRS that have a stone volume >500 mm 3 [5 && ]. Clinical trials using TFL for RIRS, have shown a median LOT of 23 min for renal stones with -Ablation efficiency: Up to 2 times higher for all stone types [9][10][11][12][13][14][15][16][17][18] Retropulsion -Always present event at low-power settings [5 && ] -Less retropulsion in comparative trials [12,25] Temperature safety Not significant difference in water temperature elevation between TFL and Ho: YAG laser if proper irrigation is performed [40]. MT, Moses technology; TFL, thulium fiber laser.…”