COMPASS Published: Experts See Level I Evidence in Support of Aspiration Thrombectomy for Stroke

Results of the COMPASS trial, which compared aspiration and stent retrievers as first-line approaches for stroke thrombectomy, are now published, providing the high-level evidence supportive of aspiration that has been lacking.

As initially reported at the 2018 International Stroke Conference (ISC), a direct aspiration first pass technique (ADAPT) was noninferior to stent retriever thrombectomy in terms of the rate of functional independence—modified Rankin Scale score of 0 to 2—at 90 days (52% vs 50%; P for noninferiority = 0.0014). Rates of intracranial hemorrhage and mortality were similar in the two groups.

The more complete results—published in the March 9, 2019, issue of the Lancet—show that the two strategies perform comparably, with aspiration having a faster time to reperfusion and lower device-related procedural costs. Those two factors could be important contributors to the choice between aspiration or stent retrievers—which have already been proven safe and effective in numerous randomized trials and have received the blessing of guideline writers—as a frontline approach for thrombectomy, according to lead author Aquilla Turk III, DO (Greenville Health System, SC).

“To me, that’s definitely a big driver of why I think ADAPT is the best way to go for the initial approach to stroke,” said Turk, who is also chief medical officer for neuroendovascular for Corindus Vascular Robotics. Aspiration has become more popular since the COMPASS results were first presented and will continue on that path now that the findings have been published, he added. “Now we have level I evidence that aspiration is as good as stent retrievers, and faster and cheaper, so I think it will shift a lot of people’s practice.”

Filling the Aspiration Evidence Gap

Stent retriever thrombectomy became an established and guideline-recommended approach for acute strokes causes by large-vessel occlusions after numerous trials—starting with MR CLEAN published in December 2014—demonstrated its safety and efficacy in selected patients. Stent retrievers soon received strong support in updated guidelines, but some neurointerventionalists worried that other techniques that had lower-quality evidence suggestive of a benefit, including aspiration, were being given short shrift.

“We’ve been doing aspiration for a long time, so we knew that that would work at least as well—and we thought even better—than stent retrievers,” Turk said.

The ASTER trial, presented at ISC 2017, started to provide some of the missing randomized evidence for the ADAPT technique versus stent retrievers. With a superiority design, the trial failed to show that using aspiration as a frontline technique improved the rate of successful reperfusion (primary outcome), but it provided support for the idea that aspiration and stent retrievers performed comparably.

The COMPASS trial, conducted at 15 North American sites, differed in that it had a noninferiority design and examined clinical outcomes for the primary endpoint. Investigators enrolled 270 patients with acute ischemic stroke caused by a large-vessel occlusion in the anterior circulation who presented within 6 hours of onset and had an ASPECTS score greater than 6.

Treating physicians could use any US Food and Drug Administration-approved device, which at the time included the Solitaire (Medtronic) and Trevo (Stryker) stent retrievers and the Penumbra aspiration system (Penumbra). Use of adjunctive technologies was allowed and was common. Distal access catheters were used in 98% of patients in the aspiration-first group and 87% of those in the stent retriever-first group. Distal aspiration was performed in 100% of cases in which stent retrievers were used in the aspiration arm and in 85% of cases in the stent retriever arm. On the flip side, at least one stent retriever was used in 21% of procedures in the ADAPT arm.

Although the median time to TICI 2b or greater reperfusion was shorter in the ADAPT arm (median 22 vs 33 min; P = 0.0194), clinical outcomes did not differ based on the which thrombectomy approach was used a first-line technique.

Both Approaches Valid

Commenting for TCTMD, Albert Yoo, MD (Texas Stroke Institute, Dallas-Fort Worth), welcomed the findings. “The absence of level I evidence was almost taken as evidence of absence of efficacy by the guidelines, so I think this sort of reassures interventionalists who believe in an aspiration-first approach,” he said.

Yoo said that the pragmatic nature of the trial—allowing for adjunctive techniques per operators’ discretion—makes it difficult to tease out the comparative efficacy of ADAPT versus a stent retriever-first approach, adding, however, that it reflects what’s happening out in practice.

“I think ultimately it’s good for the field because the more tools we have, the more effective we will be in treating our patients,” he said. To highlight the benefit of having more techniques at one’s disposal, Yoo pointed to the fact that the rate of TICI 2b reperfusion increased from about 80% with the primary modality to about 90% after additional approaches were employed.

Asked about the implications of the roughly $4,500 to $5,000 lower procedural costs by using ADAPT versus stent retrievers as a first-line approach, Yoo pointed out that costs can vary based on several factors and that the findings from COMPASS might not apply across a broader sample of centers.

I think ultimately it’s good for the field because the more tools we have, the more effective we will be in treating our patients. Albert Yoo

“It's not that interventionists shouldn't look at cost, but that the cost figures are likely variable and that interventionists shouldn't necessarily be using cost estimates from the trial as the differentiating factor for making the choice between aspiration and stent retrievers,” Yoo said.

One factor that might come into play when making that decision in the future is the composition of the stroke-causing clot, he said, noting that certain types of clots are likely more amenable to removal with one technique over another. The study of clots is, however, still in its infancy, he said.

In the meantime, Yoo said, the main message should be that “aspiration as a first-line approach is as effective as a stent retriever approach. It just gives us another effective tool, and hopefully that will change the guidelines to making people more receptive to using aspiration in treating their patients.”

He and Turk agreed that the findings of ASTER and COMPASS together are enough to place the aspiration-first approach on equal footing with stent retrievers in the guidelines. “I think aspiration does have level I evidence in support of it,” Yoo said, adding that interventionalists should be comfortable with both techniques and have a low threshold to switch if one isn’t working in order to provide the best outcomes for their patients.

Turk highlighted some advantages for the ADAPT approach, in addition to the faster time to reperfusion and lowest device costs. Of note, he said, “you don’t burn any bridges by doing it because if the aspiration doesn’t work then you still have a large catheter up at the face of the clot and through that large catheter you can now place a stent retriever and use whatever other augmented tool that you need to do the thrombectomy.”

In addition, navigating a catheter to the clot and performing aspiration may be easier than deploying a stent retriever for less experienced operators, Turk said.

But in the end, he said, “whichever way you decide to do your surgery, your patients are going to do well either way.”

In an accompanying editorial, Bijoy Menon, MD, and Mayank Goyal, MD (both Hotchkiss Brain Institute, University of Calgary, Canada), comment that it’s hard to say whether the COMPASS results should change practice.

“Neurointervention is dependent on the specialized skillset of the operator; different operators might learn, adopt, and feel comfortable with different techniques,” they write. “Neurointerventionists should, however, constantly measure their procedural outcomes (ie, speed, efficacy, and safety of reperfusion) against current benchmarks. Seen this way, the COMPASS trial offers another evidence-based approach to endovascular thrombectomy that might be used to complement or improve techniques when compared with benchmark data.”