Meta-Analysis Confirms Benefit of Stent Retrievers in Stroke

February 02, 2016

A new meta-analysis of the five recently published studies of stent retrievers in the acute treatment of ischemic stroke has confirmed that their use is associated with a significant improvement of functional independence at 90 days.

The analysis, published online in JAMA Neurology on January 25, included the MR CLEAN, ESCAPE, REVASCAT, SWIFT PRIME, and EXTEND-IA trials, found an overall significantly 72% higher likelihood of functional independence at 90 days in patients who received treatment with both tissue plasminogen activator (tPA) and stent retrievers compared with those receiving tPA alone. The number needed to treat was 6. Mortality, intracranial hemorrhage, and parenchymal hematoma did not significantly differ.

"To our knowledge, our meta-analysis is the most recent one conducted within the context of a systematic review to include all the published evidence from RCTs [randomized controlled trials] and to specifically focus on stent retrievers," the authors, led by Mark J. Eisenberg, MD, and Lahoud Touma, McGill University, Montreal, Quebec, Canada, conclude.

They add that the findings "are consistent with those of the constituent clinical trials but provide increased precision concerning the treatment effects of stent retriever therapy."

In an accompanying editorial, Raphael A. Carandang, MD, University of Massachusetts Medical School, Worcester, writes: "Although it may seem obvious from the published results of these 5 trials that there is benefit from treatment, the systematic review and meta-analysis help to more precisely quantify the benefits of stent retrievers and allay concerns about publication bias, especially in light of the early termination of 4 of the 5 clinical trials included."

The study authors first conducted a systematic review of randomized clinical trials to quantify the benefits and risks of using stent retrievers in addition to tPA vs tPA alone for the treatment acute ischemic stroke. They identified 326 publications and screened 213 potentially relevant records. This resulted in five randomized clinical trials, with a total of 1287 patients, meeting the inclusion criteria.

On pooling the data from the five trials, patients randomly assigned to stent-retriever therapy had significantly improved rates of functional independence — defined as a score of 0 to 2 on the modified Rankin Scale (mRS) — with a relative risk of 1.72.

The effect of stent-retriever therapy on all-cause mortality, intracranial hemorrhage, or parenchymal hematoma was inconclusive.

Table. Stent Retriever Meta-analysis: Results at 90 Days

Endpoint Relative Risk (95% Confidence Interval)
Functional independence (mRS score, 0 - 2) 1.72 (1.48 - 1.99)
All-cause mortality 0.82 (0.60 - 1.11)
Intracranial hemorrhage 1.15 (0.67 - 1.97)
Parenchymal hematoma 1.18 (0.71 -1.94)

 

The authors remind that the results of these five trials have recently led to new guidelines from the American Heart Association/American Stroke Association, which now strongly recommend the use of stent retrievers in acute ischemic stroke with the highest level of evidence (Class 1a). The guidelines state that stent-retriever therapy should be considered if treatment can be initiated within 6 hours of symptom onset.

They point out that the these latest recommendations apply only to patients similar to those studied in currently published randomized trials: those with imaging-confirmed stroke of the anterior circulation, most of whom were functionally independent before the index stroke and received therapy within 6 hours of stroke symptom onset.

They emphasize that only a small percentage of stroke patients meet such criteria and that further trials are needed in patients falling outside these idealized parameters.

But they conclude: "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."

Next Questions

In his editorial, Dr Carandang elaborates on the issue of the many different clinical scenarios that have not yet been addressed. These include patients who do not meet the inclusion criteria of these clinical trials and yet present within a penumbral window of opportunity; those with poor collateral circulation, unfavorable perfusion scan profiles, or a baseline mRS score of 3; those who are beyond 6 hours but have favorable collateral circulation or perfusion scan profiles.

He also asks whether MRI would help in the further selection of patients who are out of the conventional time window and whether direct interventional therapy may be an improvement over combination with tPA, as has been shown in cardiology.

He notes that the ongoing DEFUSE 3 trial seeks to address the utility of MRI and computed tomographic perfusion imaging further in selecting patients for stent-retriever therapy for stroke, and that the ongoing POSITIVE trial is investigating stent-retriever treatment in patients with stroke within 6 to 12 hours of onset.

Dr Carandang adds that other devices and techniques are also in development, including a device with a distal suction system with synergistic effect with stent retrievers (ADAPT, Penumbra Inc).

"More clinical trials are needed to address these various clinical scenarios in stroke care delivery, but we are clearly in a new era of interventional treatments and devices for acute ischemic stroke," he concludes.

No outside funding for this analysis was reported. Dr Eisenberg and Dr Carandan have disclosed no relevant financial relationships. Disclosures for study colleagues appear in the paper.

JAMA Neurol. Published online January 25, 2016. Full text Editorial

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