Yet Another Meta-analysis Finds Stent Retrievers Improve Function After Acute Stroke

Affirming the results of recent trials and meta-analyses, a new pooled analysis shows that adding stent retrievers to IV thrombolytic therapy increases the percentage of patients with acute ischemic stroke who achieve functional independence at 90 days, with no clear effect on mortality or hemorrhage risks.

“These findings are consistent with those of the constituent clinical trials but provide increased precision concerning the treatment effects of stent retriever therapy,” say researchers led by Mark Eisenberg, MD, MPH, of Jewish General Hospital/McGill University (Montreal, Canada).

Five recent trials—MR CLEAN, ESCAPE, EXTEND-IA, SWIFT PRIME, and REVASCAT—all demonstrated an improvement in functional outcomes following acute ischemic stroke by using endovascular therapy with IV thrombolytic therapy. Endovascular therapy primarily consisted of stent retrievers.

The flood of positive data represents “a watershed moment in the field,” an expert told TCTMD after results of 3 of those trials were released last year, and has sparked much discussion about how stroke systems of care need to be organized to deliver endovascular therapy to appropriate patients. In addition, the American Heart Association/American Stroke Association provided strong recommendations for the use of stent retrievers in select patients in a focused update of the stroke guidelines.

The 4 trials reported after MR CLEAN, however, were all stopped early because of benefit and as a result had relatively small sample sizes and modest numbers of events.

In the current study, published online this week in JAMA Neurology, Eisenberg and colleagues set out to better quantify the effect of stent retriever therapy by pooling data from those 5 trials, which included a total of 1,287 patients with imaging-confirmed stroke caused by an occlusion in the anterior circulation.

The primary outcome of the meta-analysis was the likelihood of achieving functional independence—modified Rankin Scale (mRS) score 0-2—at 90 days. Pooled results showed that the addition of stent retrievers increased the likelihood of that outcome (RR 1.72; 95% CI 1.48-1.99) and of having a 1-unit decrease in mRS score at 90 days (OR 2.03; 95% CI 1.65-2.50).

There were not, however, any differences in all-cause mortality (RR 0.82; 95% CI 0.60-1.11), intracranial hemorrhage (RR 1.15; 95% CI 0.67-1.97), or parenchymal hematoma (RR 1.18; 95% CI 0.71-1.94).

That “is not very surprising because the studies were not powered to find significant differences in secondary outcomes such as mortality,” an issue that could not be overcome by pooling data, lead author Lahoud Touma, also of Jewish General Hospital/McGill University, told TCTMD in email. “Larger studies would therefore be needed to be able to acquire significant data on other outcomes.”

Next Steps for Stent Retrievers

Prior meta-analyses have pooled data from trials of endovascular therapy in acute stroke, but the current differs in several ways, Touma said.

“Previous meta-analyses pooled results primarily from observational studies and nonrandomized trials comparing stent retrievers to any other therapy or were conducted outside the context of a systematic review,” he said. Using nonrandomized data “has the potential for the introduction of bias via the selection of populations, measurements of the exposures and outcomes, as well as confounding by indication,” he added. “Our more rigorous methods allow us to present a more accurate estimate of the efficacy of stent retrievers after a stroke.”

Now that efficacy has been established and the devices have been incorporated into guidelines, “future research will need to examine if benefit can still be achieved without background therapy of intravenous lytic therapy,” Anthony Bavry, MD, MPH, of North Florida/South Georgia Veterans Health System (Gainesville, FL), told TCTMD in an email. He noted, too, that “this technology is currently dependent on centers of excellence; therefore, future efforts are needed to bring this procedure to more eligible patients.”

Touma said future studies need to determine whether stent retrievers will work as well in populations that do not fit the strict inclusion criteria of the recent trials. “On the basis of the strongly positive results of this meta-analysis, however, it is expected that stent retrievers will continue to be beneficial in real-world clinical practice,” he predicted.

Source: 
Touma L, Filion KB, Sterling LH, et al. Stent retrievers for the treatment of acute ischemic stroke: a systematic review and meta-analysis of randomized clinical trials. JAMA Neurol. 2016;Epub ahead of print.

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