A fifth of patients among a chronic kidney disease (CKD) cohort on hemodialysis—a rare subset pulled from a large repository of national data—were able to come off the treatment following renal artery stenting, a team of researchers from the University of Texas (UT) Southwestern Medical Center in Dallas has found.
The findings—set to be presented at the 2024 Southern Association for Vascular Surgery (SAVS) annual meeting in Scottsdale, Arizona (Jan. 24–27)—have been hailed as being potentially the best evidence available in the field of renal stenting for decades to come, among a patient population so few in number that a randomized controlled trial (RCT) would almost never be viable, senior investigator and vascular surgeon J. Gregory Modrall, MD, a professor of surgery at UT Southwestern Medical School, told Vascular Specialist ahead of SAVS 2024.
“I have worked in the area of renal artery stenting for a number of years, but we have always focused on patients who had CKD and were not yet on dialysis,” Modrall explained.
When working on a larger study, using the TriNetX clinical database, he realized an opportunity had presented itself because of the repository’s sheer size. “It has a very large number of patients who were already on dialysis when they got stented,” said Modrall. “I realized that this presented a unique opportunity to address something that the literature is completely lacking.”
Among 173 patients who met inclusion criteria, Modrall and colleagues show that 33 (19.1%) were rescued from dialysis after stenting and were categorized as responders. At 30–90 days post-stenting, the median eGFR (estimated glomerular filtration rate) for responders was 51.6 ml/ min/1.73 m2 and remained stable over a median follow-up of 1.1 years. Survival was superior for responders, compared to non-responders, they found.
“We looked at patients who were on recent dialysis or current dialysis at the time of the renal artery stenting,” Modrall explained. “We defined recent stenting as within 60 days. The goal was to avoid inclusion of patients who maybe had dialysis six months ago but were no longer on it.
“Many of us in this field have had the sense there may be a small subset who can come off dialysis if stented at the right time but we have never had any data to guide us in patient selection, so, by and large, providers have just decided if patients are already on dialysis then they’re not going to stent that patient.
“What we found was that there is a subset that will come off dialysis—it’s about 19% of stenting patients came off in this cohort.”
Modrall and his team established that there were three basic predictors: duration of pre-stenting dialysis <79.5 days, diabetes and smoking. Two were dominant, he said. “Diabetes was a negative predictor.”
Those two dominant variables within the cohort alone “predicted 83–84% of the outcomes accurately,” Modrall continued. “So, we think that’s pretty solid data that suggest that we should be looking especially at those two variables in choosing the patients for stenting.”
With no RCT ever likely to be carried out in this subset of patients because the number who were stented in any given institution while already on dialysis are so few up to now, the data from his SAVS paper “might be the best we have for decades,” reflected Modrall.
“I personally wouldn’t stent every patient who was recently on dialysis, had renal artery stenting and was not a diabetic, because we have got to look at other factors like long-term survival, ability to tolerate the procedures, etc., but I think that is a good starting place and a lot more than we had before this study began,” Modrall added.
“It’s always going to be a difficult decision and it’s something that should be made in conjunction with a nephrologist, the patient and after looking at life expectancy and the patient’s ability to tolerate the procedure. With good education, the patient should be very active in making that decision. The chances are not high, one in five, but if we can take you off dialysis, it will have a huge impact on your life going forward.”
The ongoing larger study on which Modrall and colleagues are working revealed that patients in CKD stages 3b and 4 (eGFR 15-44 mL/min/1.73m2) are the only sub-groups with a significant probability of improved renal function after renal stenting, with the rate of decline of preoperative eGFR over the months prior to stenting a powerful discriminator of patients who are most likely to benefit.
Those results, delivered during SAVS 2023 in Rio Grande, Puerto Rico, last January, bore the ultimate aim of creating a prediction tool. At the time, Modrall pointed out that the predictors highlighted were “putative,” or “candidate predictors,” that have not been validated in a prospective series. “The next step is to take the data from this study, combine it with two of our prior studies, and in doing so we will have close to 1,800 patients with renal artery stents,” he said at the time. “That represents the single largest dataset of renal artery stenting patients in existence to my knowledge.”
Modrall and his team explained how they had hoped to leverage the enlarged dataset to create an outcome prediction tool that clinicians can use in practice. He envisaged a desktop- or phone-based application into which a patient’s parameters could be input in order to establish a probability of improved renal function.
“It turns there are variables that we haven’t defined,” he said prior to SAVS 2024. “The predictive capacity is better than we have now, but it is not as high as I’d like to see it. We are continuing to work on that.
“If I cannot get to a predictive capacity with this database that I think is sufficient, the next step would be to take a machine-learning approach to try to identify variables that maybe we haven’t even considered before.”
