(UroToday.com) In the moderated poster session for “Stone – Ureteroscopy 2,” Dr. Mitchell R. Humphreys (Mayo Clinic, Phoenix, Arizona) presented his team’s observations on the impact of laser settings for nephrolithiasis specifically using the Thulium fiber laser (TFL). They analyzed data from 8 centers from 12/2021 -4/2023 using prospective data from an international registry.
Dr. Humphreys, representing the Endourological Society’s T. O.W. E. R. (Team of Worldwide Endourology Researchers) Research Consortium, provided valuable insights into how adjustments to TFL laser settings affect the treatment of ureteral and kidney stones. Patient demographics, stone characteristics, and laser metrics are shown in Table 1.
For this study, all stones, both ureteral and kidney stones, were treated using the TFL settings listed in the table below. All surgeons used these settings for the first minute of laser time. After the first minute, surgeons were allowed to make changes at their discretion.
Dr. Humphreys revealed that surgeons often modify TFL laser settings during lithotripsy, with changes occurring in 46% of cases involving kidney stones and 60% of cases involving ureteral stones. The adjustments were more frequent for larger kidney stones and initially treated cases, reflecting a learning curve and adaptation process.
For kidney stones, the study showed that despite setting alterations, there was no significant difference in the 3-month stone-free rate between cases with adjusted settings and those with initial settings (71.22% vs 62.18%, p = 0.1236). Interestingly, in later cases, more frequent setting changes were associated with a trend toward a higher 3-month SFR (72.66% vs 61.54%, p = 0.0575).
When examining ureteral stones, setting changes did not impact the stone size or the 3-month SFR significantly (79.03% vs 92.68%, p = 0.094). However, there was a slight increase in SFR in later cases with more frequent setting adjustments (88.46% vs 80.39%, p = 0.2538).
Dr. Humphreys' findings highlight the importance of flexibility and experience in optimizing TFL laser use. Surgeons’ modifications of laser settings reflect an evolving understanding of TFL technology. The study’s data suggest that frequent adjustments are part of the learning process to better understand the capabilities of the Thulium fiber laser.
During the Q and A session, a member of the audience stated that they found TFL to ablate different stone compositions quite differently and asked if the stone composition was looked at in this study. Dr. Humphreys replied that “[They] do not, we only have Hounsfield units. Stone composition analysis was not part of this study because there was a lot of dusting so there is a lot of unknown that we have to take a surrogate from the Hounsfield units”. A second member of the audience asked Dr. Humphreys if he had any subjective feedback on whether surgeons tended to use a specific setting. Dr. Humphreys
stated the data across 8 centers was very heterogenous, but they saw that surgeons tended to make changes depending on the stone density, “if it was harder they tended to go more for the joules, for the softer they tended to go more for the frequency”. Lastly, a question arose on whether TFL causes ureteral strictures more than other lasers, what were the highest settings used for the ureter, and whether were there any guardrails for the study. Dr. Humphreys answered that there were no guardrails for this study and unfortunately, this study focused on stone-free rate so that data is not available.
Funding: This study was sponsored by Olympus Corporation of the Americas
Presented by: Mitchell R. Humphreys, MD, Mayo Clinic, Phoenix, AZ
Written by: Renai Yoon, Researcher, Department of Urology, University of California Irvine, @renaiyoon on Twitter/X during the 2024 World Congress of Endourology and Uro-Technology: August 12 -16, 2024, Seoul, South Korea