MR CLEAN at 2 Years: Sustained Endovascular Benefit in Stroke

May 27, 2016

BARCELONA — Two-year results of the MR CLEAN (Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands) trial have shown a sustained beneficial effect of endovascular therapy in patients with acute ischemic stroke and also a suggestion of a mortality benefit.

In the latest presentation from the trial at the recent European Stroke Organisation Conference (ESOC) 2016, lead investigator Yvo Roos, MD, Academic Medical Center, Amsterdam, the Netherlands, said, "We showed a very similar benefit on functional outcome at 2 years as was seen at the 90-day mark, but the 2-year results also suggest a greater reduction in mortality."

Commenting on the presentation for Medscape Medical News, president of the European Stroke Organisation, Valeria Caso, MD, University of Perugia, Italy, said the results are consistent with results at 3 months.

"We see our patients in the stroke unit for a few days and then we discharge them and often don't see them again, so it reassuring for us to see that at 2 years the results are still good," Dr Caso said. "That is wonderful."

The MR CLEAN trial was the first of several new studies reported in the past 18 months or so showing benefits of thrombectomy in patients with acute ischemic stroke with an occlusion in a major cerebral artery, with the primary results showing a clinically significant increase in functional independence in daily life at 90 days.

Professor Roos explained that until now there have been no long-term data from the endovascular trials. "This treatment is expensive and we need to know whether it is clinically effective and cost-effective over the long-term," he said. "We can start to address this by looking at the MR CLEAN 2-year results."

For the original study, 500 patients were assigned to intra-arterial treatment or to usual care alone, with 89% receiving thrombolysis with tissue plasminogen activator (tPA) before randomization. The primary outcome — the odds ratio of achieving a lower score on the modified Rankin scale (mRS; shift analysis) at 90 days — was 1.67 (95% confidence interval, 1.21 - 2.30) in favor of the intervention.

In terms of safety, mortality, symptomatic intracerebral hemorrhage, and serious adverse events did not significantly differ between the two groups.

For the long-term follow-up, an extension part of the trial was conducted. Professor Roos explained that this extension phase only received funding in 2013 when the main part of the trial was already well underway, so patients had to be reinvited for consent into the extended follow-up. Not all patients consented to long-term follow-up, and some patients were already past the 2-year follow-up mark or were untraceable, so there were fewer patients in the extension phase than in the main trial.

The follow-up was conducted by telephone interview by an experienced trial nurse.

"The main MR CLEAN trial was not powered for an extended follow-up, and we also lost quite a few patients to follow-up because of the late start of the extension," coinvestigator, Lucie A. van den Berg, MD, Academic Medical Center, Amsterdam, the Netherlands, commented to Medscape Medical News. "But we still had 391 patients, which is a sufficient number to estimate an effect."

Professor Roos reported that "with almost 200 patients in each group available for follow-up at 2 years, we see a very similar result in the primary outcome than we did at 3 months, with an odds ratio of achieving a lower score on the mRS scale of 1.68. That is statistical significant and is still a huge effect."

Results also suggested a favorable effect of the intervention on mortality, with 38% of the control group having died by 2 years vs 30% of those who received endovascular treatment.

Dr van den Berg elaborated that these mortality figures relate just to patients in whom a mRS score was available at 2 years and who were included in the ordinal regression analysis.

However, she noted that the researchers were also able to retrieve vital status information on patients who did not agree to be contacted by telephone during 2 years of follow-up (nonconsenters for the extension) via the Dutch Death Register.

"Therefore we had a vital status in 459 patients at 2 years of follow-up," she noted. These data showed a mortality rate of 59/212 (27.8%) in the intervention group vs 82/247 (33.2%) in the control group, an absolute reduction of 5.4 percentage points.

Professor Roos reported that few major vascular events occurred: 6 in the intervention group vs 4 in the control group; with ischemic strokes in 2 and 3 patients, respectively.

He concluded that "the effect of intra-arterial therapy on functional outcome at 2 years is similar to the effect at 3 months, but there appears to be a greater mortality benefit on long-term follow-up."

MR CLEAN was supported by the Dutch Heart Foundation and by unrestricted grants from AngioCare Covidien/ev3, Medac/Lamepro, and Penumbra.

European Stroke Organisation Conference (ESOC) 2016. Presented May 12, 2016.

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