But subgroup analyses in three of the four studies (EXTEND-IA with a total of 70 patients was too small for subgroup analyses) showed no subgroup of patients who failed to benefit from embolectomy, including elderly patients who in some cases were nonagenarians.
The unusual confluence of having four major trials showing remarkably consistent results meant that the stroke experts gathered at the meeting focused their attention not on whether stent retrievers should now be widely and routinely used in appropriate patients but instead on how this technology will roll out worldwide.
“From here on out we are obligated to treat patients with this technology at centers that can do this, and we are obligated to have more centers that can provide it,” said Dr. Kyra J. Becker, professor of neurology and neurological surgery and codirector of the Stroke Center at the University of Washington, Seattle. Dr. Becker had no involvement in any of the stent retriever trials. “I had been a doubter of this technology,” primarily because results reported at the International Stroke Conference a couple of years ago failed to prove the efficacy of clot retrieval in ischemic stroke patients, she noted. “Our ability to select appropriate patients and do it in a timely fashion hadn’t gotten to where it had to be until now,” Dr. Becker said in an interview.
“We only enrolled patients with blockages, we treated them quickly, and we used much better devices to open their arteries,” Dr. Saver added, explaining why the new studies succeeded when earlier studies had not.
The trial led by Dr. Saver, SWIFT-PRIME (SOLITAIRE™ FR With the Intention for Thrombectomy as Primary Endovascular Treatment for Acute Ischemic Stroke), enrolled 195 patients at 39 sites in the United States and in Europe. At 90 days after treatment, 59 patients (60%) among those treated with thrombolysis plus embolectomy had a modified Rankin Scale score of 0-2, compared with 33 patients (36%) among those treated only with thrombolysis (in this trial intravenous treatment with tissue plasminogen activator), a highly significant difference for the study’s primary endpoint.
“For every two and half patients treated, one more patient had a better disability outcome, and for every four patients treated, one more patient was independent at long-term follow-up,” Dr. Saver said. Safety measures were similar among patients in the study’s two arms.
The EXTEND-IA results showed a 90-day modified Rankin Scale score of 0-2 in 52% of the embolectomy patients, compared with 28% of those treated only with thrombolysis. The study’s co–primary endpoints were median level of reperfusion at 24 hours after treatment, 100% with embolectomy and 37% with thrombolysis only, and early neurologic recovery, defined as at least an 8-point drop from the baseline in the National Institutes of Health Stroke Scale score or a score of 0 or 1 when assessed 3 days after treatment. Patients met this second endpoint at an 80% rate with embolectomy and a 37% rate with thrombolysis only. Results of EXTEND-IA appeared in an article published online concurrently with the meeting report (N. Engl J. Med. 2015 Feb. 11 [doi:10.1056/NEJMoa1414792]).
The third, and largest, of the three studies presented at the conference, ESCAPE (Endovascular Treatment for Small Core and Anterior Circulation Proximal Occlusion with Emphasis on Minimizing CT to Recanalization Times), enrolled 316 patients at 11 centers in Canada, 6 in the United States, 3 in South Korea, and 1 in Ireland. After 90 days, 53% of patients in the embolectomy arm had achieved a modified Rankin Scale score of 0-2, this study’s primary endpoint, compared with 29% of patients in the thrombolysis-only arm (treatment with alteplase). These results also appeared in an article published online concurrently with the conference report (N. Engl. J. Med. 2015 Feb. 11 [doi:10.1056/NEJMoa1414905]).
SWIFT PRIME was sponsored by Covidien, which markets the stent retriever used in the study. Dr. Saver and Dr. Goyal are consultants to Covidien. EXTEND-IA used stent retrievers provided by Covidien. ESCAPE received a grant from Covidien. Dr. Becker had no relevant disclosures.
mzoler@frontlinemedcom.com
On Twitter @mitchelzoler
Views on the News
Results warrant embolectomy scale-up
Many U.S. centers have interventionalists who already perform endovascular treatments within intracerebral arteries, but the issue is can they do this form of embolectomy in the high-quality, highly-reliable, rapid way that it was done in these trials? Stent-retriever catheters are relatively straightforward to use by operators who are experienced doing vascular procedures in the brain, but they don’t deliver this treatment by themselves. You need a team that is focused on doing it quickly, and that will be the kind of training we’ll need to roll out this treatment broadly. We achieved it for stroke thrombolytic treatment through the Target Stroke program (JAMA 2014;311:1632-40), so we know that we can achieve this sort of goal. Delivering embolectomy requires more people and more technology than thrombolysis, but it is not rocket science; it just needs a system.