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WSC 2022 | Individual patient data meta-analysis of direct thrombectomy versus bridging thrombolysis

Urs Fischer, MD, Basel University Hospital, Basel, Switzerland, and Yvo B. Roos, MD, PhD, Amsterdam University Medical Center, Amsterdam, The Netherlands, discuss the findings of an individual patient data meta-analysis looking at direct mechanical thrombectomy (MT) versus bridging intravenous thrombolysis (IVT) with alteplase followed by MT for the treatment of acute ischemic stroke due to large vessel occlusion. Whether the addition of IVT adds benefit beyond what can be achieved with MT alone is still a topic of worldwide debate. To address this question, an individual patient data meta-analysis was performed, pooling data from six recent randomized, controlled trials evaluating direct MT versus MT with prior IVT. Good functional outcome at 90 days (modified Rankin scale 2) was used as the primary outcome to test non-inferiority of direct MT, using a 5% non-inferiority margin. Overall, there were 1153 patients in the direct MT arm and 1160 in the IVT plus MT arm. The results showed a trend towards benefit of bridging therapy over direct MT, but this difference was not statistically significant. However, the analysis was unable to show the non-inferiority of direct MT, compared to bridging therapy. The rates of successful reperfusion were significantly higher in the IVT plus MT group, compared to the direct MT group, but rates of intracerebral hemorrhage were also higher in this group. This interview took place at the World Stroke Congress 2022 in Singapore.

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Transcript (edited for clarity)

Yvo B. Roos:
I think it’s important to notice that everything we told today is only regarding patients which are directly presented to a comprehensive stroke center.
So all the six trials which were included in our meta-analysis, included only patients which were directly brought to a comprehensive stroke center, so a center capable of doing both intravenous treatments and endovascular treatment...

Yvo B. Roos:
I think it’s important to notice that everything we told today is only regarding patients which are directly presented to a comprehensive stroke center.
So all the six trials which were included in our meta-analysis, included only patients which were directly brought to a comprehensive stroke center, so a center capable of doing both intravenous treatments and endovascular treatment. So our data is not telling something about patients being transported to a primary stroke center. A primary stroke center capable of intravenous thrombolysis, the patients over there should be treated with intravenous thrombolysis when suitable as quickly as possible. That’s something I want to say upfront.
So what we did is that we took the data from the six trials all over the world, which were looking at the same thing, whether bridging therapy with intravenous thrombolysis and endovascular treatment was still, let’s say, better than going for direct thrombectomy.

And what we did is that we used all the data, we put it together. And well, what we saw is that the difference is not that different. Urs is going to tell you exactly what we did for the analysis. But the problem is that we are not talking about superiority of one of the other treatments, we’re talking about non-inferiority. And that’s always very difficult to understand.
When you talk about non-inferiority, you need to talk about the boundary of non-inferiority. In this case, we choose for a boundary of 5%, which was a boundary which we got from interviewing many, many, many experts in the world, we published a paper on that. And they said, “Well, if the treatment with going directly for endovascular treatment is not more than 5% different, then I would go for this direct treatment. But if you can’t show that the difference is, let’s say, less than 5%, if it’s going to be, then we should stick with the standard treatment, which is the combination.”
So we chose the 5% difference for this non-inferiority design and that’s how we started and that’s how we did the analysis and maybe Urs, you can tell what we did find.

Urs Fischer:
Yeah, thanks. So overall, there were 1,153 patients in direct mechanical thrombectomy arm and 1,160 patients received bridging thrombolysis.
So overall, there was on a first glimpse on the Grotta bars of the distribution of the modified Rankin Scale, there was a trend that patients with bridging thrombolysis perform better than patients treated with direct mechanical thrombectomy. However, the so-called adjusted common odds ratio was 0.89 and the 95-confidence interval was from 0.76 to 1.04. So this difference was not statistically significant.

However, we were not able to show the non-inferiority of the direct mechanical thrombectomy approach compared to bridging thrombolysis. So what does that mean and what is the clinical implication? Basically, we could not show that direct mechanical thrombectomy is better, however, we could also not show that it is equally effective. And therefore, most physicians in the future, they will continue treating patients with large vessel occlusion with intravenous thrombolysis and then will proceed with endovascular therapy.
However, if you look at the subgroups, the rates of good functional outcome defined as Modified Rankin Scale of 0 to 2 was 49% in the direct mechanical thrombectomy group and 51% in the bridging arm. So that’s only a difference of 2%, which was statistically not significant.

However, what we could show that successful reperfusion was significantly better in patients receiving bridging thrombolysis compared to direct mechanical thrombectomy. However, rates of any intracerebral hemorrhages were higher in the bridging arm than in the direct mechanical thrombectomy arm, but not symptomatic intracerebral hemorrhage.
So that means that if you treat patients with a large vessel occlusion, you have a small benefit regarding better reperfusion in patients with bridging thrombolysis, however, you have to pay that with an increased risk of any intracerebral hemorrhage.

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Disclosures

Prof. Fischer reports the following disclosures:
-research grants from Medtronic (BEYOND SWIFT, SWIFT DIRECT) and from Stryker, Rapid medical, Penumbra and Phenox (DISTAL).
-consultancies for Medtronic, Stryker, and CSL Behring (fees paid to institution).
-participation in an advisory board for Alexion/Portola and Boehringer Ingelheim (fees paid to institution).