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LOS ANGELES -- Which mechanical thrombectomy tool clinicians reach for first in large vessel ischemic strokes may not make much difference in outcomes, the COMPASS trial showed.

Aspiration as the initial strategy was noninferior to initial stent retriever use for good functional outcomes at 90 days (52% versus 49% modified Rankin Scale score 0-2, P=0.0014 for noninferiority with a margin excluding any more than 7% worse).

Nor was there any differential shift in the overall Rankin scores, J Mocco, MD, of Mount Sinai Hospital in New York City, and colleagues reported here at the International Stroke Conference.

Time to substantial reperfusion and the quality of the reperfusion, in terms of proportion of blood flow restored, were statistically comparable between groups, although initial aspiration held consistent numerical advantages.

Safety was nearly identical between the two strategies for 90-day all-cause mortality and intracranial hemorrhage, both overall and symptomatic.

"Now we have level I evidence that stent retrievers and primary aspiration have equivalent clinical outcomes in large vessel occlusion," Mocco concluded at a press briefing for the late-breaking clinical trial session.

Ralph Sacco, MD, of the University of Miami and president of the American Academy of Neurology, said he wasn't so sure that the evidence has risen to what guidelines committees would consider class Ia.

He cautioned that noninferiority designs don't always prove equivalence. "I think it's grade A evidence. Is it level I? It's getting pretty close."

"The important thing is all of these tools are helpful, the question is what do you start with," he added. "What COMPASS unequivocally shows is you don't have to open the stent retriever. If you go up with the catheter, do aspiration, and that works ... then you're done. If it doesn't work, then you use that same catheter that is already up by the clot to put [in] the stent retriever and grab the clot."

The COMPASS "data are a bit more robust for aspiration compared to the previously, technically-driven trial, ASTER," he added. That French trial had shown closer similarity across endpoints than COMPASS, which Mocco suggested might be accounted for by newer devices and catheters in the latter.

While formal cost analysis of the trial has not yet been completed, press conference moderator Bruce Ovbiagle, MD, of the Medical University of South Carolina in Charleston, noted that this will be a factor in clinical choice as well.

The aspiration technique has been suggested as a less expensive approach, by eliminating need for a roughly $6,000 stent retriever device. In the aspiration-first arm of COMPASS, only 20.9% of patients received stent retriever treatment as a second device due to failure or in attempt to improve flow.

The proportion achieving at least substantial reperfusion (TICI 2b flow) with the primary modality was similar between groups (83.2% aspiration versus 81.3% stent retriever, P=0.75).

The investigator-initiated head-to-head trial included 270 patients randomized to the two treatment strategies at 15 centers, which were balanced between those doing mostly aspiration-first thrombectomy and those doing most cases stent-retriever first as well as a few with no clear preference.

Mocco cautioned that the data should be considered preliminary, as small changes may be made if one patient must be excluded due to consent problems that were just discovered and are under investigation by the group.

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