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HONOLULU -- Patients with large-core strokes didn't share the same benefits of endovascular therapy with peers presenting with smaller ischemic cores, according to one study reported here, though another suggested that core volume did not change the treatment effect of late thrombectomy.

With data pooled from the SELECT and TREVO studies, 187 patients were stratified by ischemic core volume, i.e., the amount of tissue with regional cerebral blood flow (rCBF) <30% on CT perfusion imaging. Outcomes were worse with larger ischemic cores, according to Amrou Sarraj, MD, of UT McGovern Medical School in Houston:

• 90-day modified Rankin Scale (mRS) score 0-2: 45% for ischemic cores <50 mL vs 29% for 50-100 mL vs 11% for >100 mL (P=0.018)
• Symptomatic intracerebral hemorrhage: 2% vs 7% vs 33% (P=0.002)
• Neurological worsening (NIH Stroke Scale score decline by 4+ points at 24 hours): 3% vs 18% vs 56% (P<0.001)
• Mortality at 90 days: 11% vs 29% vs 33% (P=0.019)

Along with perfusion core volumes, increasing time to reperfusion was also tied to poor rates of functional independence and growing rates of mortality and symptomatic hemorrhage, Sarraj said at a late-breaking trial session at the .

Nearly one in ten patients in the study had ischemic core volumes above 100 mL.

"It isn't particularly surprising that strokes with large cores do poorly with endovascular therapy. Is there room for improvement with treatment? Future trials will tell but a floor effect may be a problem," commented S. Claiborne Johnston, MD, PhD, of the University of Texas at Austin Dell Medical School, who was not involved in the trial.

"At some point we need to think about diminishing returns, particularly when we are considering the kinds of outcomes patients want. Many patients would find a stroke with mRS=5 an outcome not worth pursuing or even worse than death," Johnston told MedPage Today.

SELECT was a non-randomized study comparing thrombectomy vs medical management, and TREVO, a post-marketing registry for the stent retriever from Stryker.

Together they showed that good outcomes were not common once infarct cores grew beyond 100 mL. However, thrombectomy in these cases may still be better than medical management, Sarraj suggested.

Given the lack of medical management controls in the present study, randomized clinical trials are needed to answer that question, he emphasized.

His SELECT 2 is one such trial that plans to enroll 460 patients with large cores (ASPECTS 3-5 and rCBF [<30%] volumes at 50-100 mL), the presenter noted.

Studies in large-core strokes mark the evolution of endovascular therapy, which had been proven beneficial at first for small cores in the early stage, then more recently for small cores at a later window.

"The exciting news is that this study suggests like a few others that we may be able to offer mechanical thrombectomy to patients currently being excluded on the basis of a large stroke core volume," according to Demetrius Lopes, MD, of Advocate Lutheran General Hospital in Park Ridge, Illinois.

Yet in a separate analysis by the same group -- also reported here, with a simultaneous journal publication -- outcomes with late thrombectomy did not differ with infarct core size.

A subgroup analysis from DEFUSE 3 involved stroke patients undergoing thrombectomy 6-16 hours from who were either transferred from another hospital or directly admitted to the endovascular-capable center.

Among its findings were that no heterogeneity in the thrombectomy treatment effect was seen in transferred patients when stratified by ischemic core volume (either on CT perfusion or diffusion-weighted imaging) or by ASPECTS, Sarraj and colleagues reported.

Two-thirds of the 182 people randomized in the DEFUSE 3 cohort had been transferred for endovascular therapy.

The new analysis mainly focused, however, on comparisons between the transfer cohort and direct arrivals. The former waited a median 26 minutes longer to get to the thrombectomy center (9.43 vs 9 hours from last known well to study site arrival). For the most part, there were no differences in outcomes:

• 90-day mRS score shift: transfer OR 2.6 vs direct OR 2.9
• Overall functional independence (mRS score 0-2): 45% vs 44%
• Thrombectomy treatment effect: OR 3.1 vs OR 2.0

"Thrombectomy reperfusion rates, mortality, and symptomatic intracranial hemorrhage rates did not differ," the investigators added in their study published online in .

"Both direct and transfer patients who received endovascular thrombectomy had significantly better outcomes than patients receiving medical management, with similar safety profiles," they concluded. "These results have health care implications indicating transferring potential candidates for late-window thrombectomy associated with substantial clinical benefits and should be encouraged."

The trial had imaging-based enrollment criteria requiring that each participant have a large-vessel anterior circulation occlusion and initial infarct smaller than 70 mL, mismatch ratio of at least 1.8, and mismatch volume at least 15 mL.

Findings of the present analysis fall in line with another recent DEFUSE 3 analysis showing the generalizability of thrombectomy's benefits to a broad patient population even 6-16 hours after stroke onset.