Low-Intensity Ultrasound Shatters Kidney Stones in 70% of SOUND Trial Patients

WASHINGTON — An in-office device that uses low-pressure ultrasound waves to breaking up kidney stones was safe and effective, according to data from the SOUND trial.

Treatment with the Break Wave lithotripsy device reduced stones to passable fragments of ≤4 mm in seven out of 10 patients and with minor complication, reported Benjamin Chew, MD, of the University of British Columbia in Vancouver.

“Break Wave offers a safe and efficacious non-invasive and anesthesia-free treatment option at any healthcare setting.” Chew said in a presentation at the AUA annual meeting. The device received FDA clearance in January, according to the developer, while in May, the company got the FDA green light for the next-generation Break Wave device.

SOUND had 64 adults with an upper urinary tract stone that had to be >4 mm and ≤10 mm on CT; indicated for extracorporeal shock wave lithotripsy (ESWL) per American Urological Association (AUA) criteria; and be individually separable from other stones.

Chew reported that that 94% of the procedures were completed in clinic settings, which speaks to the device’s portability and workflow flexibility. In addition, all patients tolerated treatment without anesthesia or sedation, eliminating pre-op clearance, post-anesthesia care unit recovery, and anesthesiology support.

Break Wave met its primary endpoint by demonstrating non-inferiority to ESWL, with 70% of patients with being stone free or with stone fragments of ≤4 mm (95% CI 57.6%-80%, P=0.0016).

The study also met its primary safety endpoint of non-inferiority to EWSL, as patients experienced no clinically significant or symptomatic hematoma, urinary tract sepsis, or serious cardiac arrhythmia with Break Wave.

Chew pointed out that while both ESWL and Break Wave Lithotripsy are noninvasive, the latter works by delivering ultrasonic waves to the stone through the creation of standing stress waves. This is akin to “an opera singer sings at a resonant frequency that will shatter glass,” he explained.

“And if you think of shock wave as one big shock that’s up to about 45 megapascals — like a boxer hitting a very heavy punching bag — Break Wave is also that same boxer, but doing little punches on a speed bag, and instead of 45 megapascals, it’s up to 8,” he added. “And this is why patients do not require any sedation or anesthesia for this. Shock wave will also result in something like fragmentation, where you’re breaking the stone up into giant fragments, whereas Break Wave will break it up into little bits of dust, particularly from the periphery.”

Patients had an averarge age of 50, and 39.1% were female. About 58% had a history of experiencing any stone. The mean stone size was 7.8 mm (renal stones were 8.3 mm and ureteral stones 7.3 mm), and more than one-third were ≥1,000 HU units on CT. Chew said that 41% of patients were excluded because they presented with an acoustic window that limited the ability to deliver Break Wave to the target stone.

Half of the the stones were in the kidney and the other half in the ureter, with about one-third in the urethrovesical junction (UVJ) and 29.7% in the lower pole.

The Break Wave therapy delivery time was on average 29.7 minutes, and the procedure-t0-discharge time was about 14 minutes. The mean pain score was 2.0 (on a scale of 1-10 with 10 the worst). About a quarter (27%) required retreatment with Break Wave. Chew did not state why retreatment was needed, but in a 2024 study of Break Wave in 44 patients, his group explained that “[a]s BWL is an ultrasound-based technology, certain stone locations such as the proximal and midureter, and some upper pole stones, are not amenable to BWL due to inability to identify the stone with ultrasound, or obstructing anatomical features such as bowel, lung, rib/pelvic bones, and depth.“

Adverse events that were mostly mild in nature and consistent with those of EWSL, including transient hematuria and pain. “Importantly, no patient required immediate, unplanned intervention,” Chew said.

The success rate was 52% in the kidney and 87% in the ureter, 90% in the UVJ, and 47% in the lower pole, “which we know are harder,” Chew said, noting that that next-gen Break Wave device has therapy probes with 31% smaller footprint, “which should be able to capture a lot more of those patients.” In a sample of 11 patients, these smaller probes had improved stone-free rates compared with the original SOUND probes (64% vs 48%), he reported.