Steerable ureteroscopic renal evacuation shows promise for kidney stone removal

Steerable ureteroscopic renal evacuation (SURE) using the CVAC Aspiration System (CVAC) demonstrated noninferiority vs standard ureteroscopy (URS) for kidney stone removal, according to findings from the prospective, randomized ASPIRE study presented at the 2024 AUA Annual meeting.¹

The data for the primary end point of SFR showed that the zero fragments rate (1.25 mm CT) was 47.8% in the SURE arm vs 49.1% in the URS arm, for a difference of -1.3% (90% CI, -17.7% to 15.2%) and a P value for noninferiority of .027.

The multicenter ASPIRE study evaluated the safety and efficacy of SURE compared with URS in patients who were candidates for URS laser lithotripsy who had 1 or more renal stone and a total stone burden of 7 mm to 20 mm. Enrolled patients were randomized in a 1:1 ratio to receive SURE (n = 46) or URS (n = 55).

“SURE was performed using CVAC, a novel steerable catheter system with dedicated irrigation and aspiration lumens capable of removing stone fragments <2.5 mm,” explained lead study author Brian Matlaga, MD, a professor of urology at The Johns Hopkins University School of Medicine and executive medical director of clinical affairs for Johns Hopkins Medicine International. He added that most of the URS done on the trial was basketing and noted that, “You weren’t prevented from [also receiving] basketing if you were randomized to the SURE arm.”

The mean patient age in the SURE arm was 58.8 years, the mean BMI was 31.8, 52.2% of patients were male, and 47.8% were female. Total stones burden (Core Lab) was 14.5 +/- 6.5 mm and total stone volume was 485.0 +/- 432.5 mm³. A little over half (56.5%) of patients had a single stone, 58.7% had a lower pole stone, and 30.4% had ureteral stones.

In the URS arm, the mean patient age was 59.8 years, the mean BMI was 30.5, 50.9% of patients were male, and 49.1% were female. Total stones burden (Core Lab) was 19.1 +/- 10.6 mm and total stone volume was 713.0 +/- 558.5 mm³. Across the cohort, 43.6% of patients had a single stone, 45.5% had a lower pole stone, and 18.2% had ureteral stones.

Matlaga said that patient demographics were mostly balanced between the 2 arms. He did note, however, that there was a difference in the stone size volume, with the SURE arm being slightly smaller.

The study was powered for noninferiority with the primary end point being the stone free rate (SFR), defined as zero residual fragments on 1.25 mm CT at 30 days. Secondary end points included stone clearance (percent reduction in stone volume) and residual stone volume.

The data for the primary end point of SFR showed that the zero fragments rate (1.25 mm CT) was 47.8% in the SURE arm vs 49.1% in the URS arm, for a difference of -1.3% (90% CI, -17.7% to 15.2%) and a P value for noninferiority of .027. “The aspiration device performed just as well as standard URS,” said Matlaga.

For the secondary end points, stone clearance was 96.9% with SURE and 92.9% with URS, for a difference of 4% (90% CI, 0.9% - 7.1%) and a superiority P value of .036. Residual stone volume was 14.3 +/- 30.9 mm³ vs 70.2 +/- 144.9 mm³, respectively, for a difference of -55.9 mm³ (90% CI, -92.0 to -19.7) and a superiority P value of .012.

Matlaga said the results also revealed that, “As the stones get bigger, aspiration does a better job than URS with the percentage of the stones that are taken out and the amount that’s left behind is less.”

The safety results at 30 days’ follow-up were similar between the SURE and URS arms. The safety populations consisted of 67 patients in the SURE arm and 65 patients in the URS arm. Per Clevien-Dindo event classification, adverse events of grade I, II, IIIa, IIIb, and IV in the SURE vs URS arms were 14.9% vs 9.2%, 10.4% vs 6.2%, 0% vs 0%, 4.5% vs 1.5%, and 0% vs 0%, respectively. No patients in either arm required a second URS. In the SURE arm, 4.5% of patients had a stent exchange vs no patients in the standard URS arm.

“Aspiration with CVAC is safe and is not significantly different compared with URS for stone free rate. Additionally, it probably gets more stone volume out compared to what you are used to with basketing,” concluded Matlaga, adding that, “SURE outcomes are independent of baseline stone volume.”

Matlaga also reported some recently obtained findings from the trial showing that early analysis of ASPIRE 1-year data indicate that patients treated with SURE have to go back to the ER during the first year following the procedure less frequently compared with those receiving URS (P = .015).

Regarding next steps with this study, Matlaga said, “Future stone events and retreatment will be assessed through 2 years.”

Reference

1. Matlaga B, Mueller T, Johnson B, et al. Prospective, randomized study of steerable ureteroscopic renal evacuation vs ureteroscopy with basketing: 30-day results of the ASPIRE study. Presented at: 2024 American Urological Association Annual Meeting. May 2-6, San Antonio, Texas. Abstract PD10-04.