Title
Endovascular Thrombectomy May Still Help in the Largest Strokes: What the LASTE Ancillary Analysis Adds
Highlights
In an ancillary analysis of the randomized LASTE trial, endovascular thrombectomy (EVT) improved 90-day functional outcomes and reduced mortality in patients with the largest baseline infarcts, defined by ASPECTS 0-2.
The treatment effect was clinically meaningful despite very large infarct cores, with a substantial shift toward better modified Rankin Scale outcomes and less infarct growth on 24-hour imaging.
These findings challenge the longstanding practice of using infarct size alone to deny EVT, at least in patients younger than 80 years treated within 6.5 hours and selected largely with MRI.
Safety remained a concern, as symptomatic intracranial hemorrhage was numerically higher with EVT, reinforcing the need for careful patient selection and informed risk discussion.
Background
For more than a decade, endovascular thrombectomy has been one of the most important advances in acute ischemic stroke care. Randomized trials have consistently shown that removing a proximal large-vessel occlusion can improve survival and functional independence, particularly when treatment is delivered quickly. However, much of that evidence came from patients with relatively small to moderate infarct cores at baseline.
Patients with very large established infarcts have remained a difficult group. In clinical practice, they are often excluded from thrombectomy because clinicians worry that little salvageable tissue remains, the risk of hemorrhagic transformation is higher, and meaningful recovery may be unlikely even if reperfusion is successful. ASPECTS, the Alberta Stroke Program Early CT Score, is a 10-point imaging scale used to estimate early ischemic change in the middle cerebral artery territory; lower scores indicate larger infarcts. An ASPECTS of 0-2 generally signals a very extensive stroke burden and has historically been considered a poor prognostic marker.
At the same time, the field has been moving toward a more nuanced view. Larger infarcts do not necessarily mean zero benefit, especially if some tissue can still be rescued, if the occlusion is severe but the collateral circulation remains partly functional, or if reperfusion can prevent further infarct expansion. That uncertainty is what makes the LASTE ancillary analysis clinically relevant.
Study Design
This report is a post hoc ancillary analysis of the multicenter randomized LASTE trial. The parent study enrolled patients 80 years or younger with proximal anterior circulation large-vessel occlusion, ASPECTS 0-5, and randomization within 6.5 hours of last known well. The present analysis focused specifically on the subgroup with ASPECTS 0-2, representing the largest baseline infarcts without an upper size limit.
Patients were randomized to EVT plus medical care or medical care alone. The key efficacy endpoint was the distribution of the modified Rankin Scale (mRS) score at 90 days, a standard measure of post-stroke disability ranging from 0 (no symptoms) to 6 (death). Secondary endpoints included mortality, infarct volume growth at 24 hours, symptomatic intracranial hemorrhage, and mRS at 180 days. The trial was conducted and reported in accordance with CONSORT principles.
Importantly, the subgroup was predominantly selected using magnetic resonance imaging, which may have influenced the certainty with which infarct size and tissue status were assessed. That feature matters for interpreting generalizability to centers that rely mainly on noncontrast CT and CT angiography.
Key Findings
Among 181 patients with ASPECTS 0-2, the median age was 72 years and 55.8% were women. The median core volume was 156 mL, with an interquartile range of 121-204 mL, indicating a population with truly extensive baseline ischemic injury.
At 90 days, EVT was associated with better functional outcome distribution across the entire mRS scale, with a generalized odds ratio of 1.81 (95% CI, 1.32-2.47). In practical terms, this means the chance of landing in a better disability category was substantially higher with thrombectomy than with medical care alone. Because the mRS is ordinal rather than binary, this shift analysis is particularly informative: benefit was not limited to one threshold, but extended across the full spectrum of post-stroke disability.
Mortality was also lower in the EVT group. Death occurred in 38.4% of EVT-treated patients versus 59.6% of patients who received medical care alone, corresponding to a relative risk of 0.64 (95% CI, 0.47-0.89). This is a notable absolute difference in a population at high risk of death or severe disability.
One of the most clinically relevant findings was the increase in the proportion of patients achieving mRS 0-3 at 90 days: 31.4% in the EVT group versus 8.5% in the medical care group, for a relative risk of 3.69 (95% CI, 1.77-7.68). Although many patients still had substantial disability, the intervention meaningfully increased the likelihood of a survival-with-function outcome rather than survival with profound dependency or death.
Imaging also supported a biological effect. Infarct growth at 24 hours was significantly reduced with EVT, with a mean difference of -70.3 mL (95% CI, -94.2 to -46.3). This suggests that even when baseline infarcts are large, reperfusion can still limit secondary expansion of ischemic injury. In acute stroke, preventing further tissue loss can be the difference between severe hemiplegia, consciousness impairment, and a more survivable, rehabilitatable deficit.
Safety outcomes warrant careful attention. Symptomatic intracranial hemorrhage occurred in 12.9% of EVT-treated patients versus 4.5% in the medical care group, corresponding to a relative risk of 2.85 (95% CI, 0.94-8.60). Although the confidence interval crossed unity, the point estimate and absolute rates indicate that hemorrhagic risk may be higher with thrombectomy in this population. For clinicians, this is a reminder that efficacy does not eliminate risk; it reframes the trade-off.
Longer-term outcome at 180 days was also assessed, reinforcing the durability of the general functional signal, although the core abstract emphasizes the 90-day results as the primary driver of interpretation. In acute stroke trials, 90-day disability remains the accepted benchmark because it captures both early survival and medium-term recovery potential.
Clinical Interpretation
The principal message from this analysis is that very large infarct burden should not be viewed as an automatic contraindication to EVT in otherwise eligible patients under 80 years of age treated within an early time window. This is a meaningful shift in thinking because many treatment pathways still treat low ASPECTS as a near-futility marker. The LASTE data suggest that even among patients with ASPECTS 0-2 and median core volumes around 156 mL, reperfusion can reduce infarct expansion and improve the odds of better functional recovery.
However, the result should be interpreted in context. This was a post hoc subgroup analysis rather than the primary randomized comparison of a trial specifically designed for ASPECTS 0-2. That means the finding is stronger than a retrospective observational report, but still less definitive than a dedicated trial powered for this subgroup. The confidence intervals are encouraging, yet subgroup analyses are inherently more vulnerable to chance findings and residual confounding in the way included patients were selected.
Generalizability is another issue. The cohort was limited to patients younger than 80 years, treated within 6.5 hours, and predominantly selected by MRI. Patients older than 80, those presenting later, and those triaged using CT-only pathways may not experience the same balance of benefit and harm. Additionally, the anatomy was proximal anterior circulation large-vessel occlusion; the results should not be extrapolated to distal occlusions or posterior circulation strokes without caution.
From a practical standpoint, the study supports a more individualized decision-making model. Rather than using infarct size alone as a binary exclusion criterion, stroke teams may need to consider age, time from last known well, occlusion site, collateral status, baseline disability, perfusion status, and patient/family goals. In other words, large infarct core should be treated as one component of prognosis, not the whole story.
The hemorrhage signal also matters for informed consent and bedside counseling. Patients with very large infarcts may still benefit, but the expected benefit is not the same as in patients with smaller cores, and the procedural risk profile is less favorable. Shared decision-making should therefore explicitly address the possibility of survival with moderate disability, survival with severe disability, and the competing risk of intracranial bleeding.
How This Fits With the Broader Evidence
Until recently, the strongest thrombectomy evidence largely came from trials enrolling patients with smaller infarcts and more favorable imaging profiles. That led many guidelines and institutions to emphasize ASPECTS thresholds when deciding eligibility. More contemporary studies have increasingly explored whether these thresholds should be relaxed. The LASTE ancillary analysis aligns with the direction of this evolving literature: benefit may extend into patients with more extensive infarction than previously assumed, especially when treatment is early and patient selection is careful.
Still, the field is not yet settled. Different trials have used different imaging methods, thresholds, and enrollment strategies, which complicates direct comparison. Some studies suggest benefit in low ASPECTS populations; others raise concern about increased hemorrhage or diminished net clinical gain. The most reasonable synthesis is that the question is no longer whether large infarcts can ever benefit from EVT, but which large infarct patients are most likely to benefit enough to justify the risk.
Limitations
This analysis has several limitations. First, it is post hoc and limited to a subgroup, which can inflate the possibility of selective interpretation. Second, the sample size of 181 patients, although meaningful for a rare and severe population, still limits precision around safety outcomes such as symptomatic hemorrhage. Third, the imaging approach was predominantly MRI-based, which may identify core extent differently than CT-based workflows. Fourth, the analysis applies only to patients treated within 6.5 hours and aged 80 years or younger, so external validity is restricted.
Another important limitation is that ASPECTS and automated core volume are imperfect surrogates for irreversible tissue injury. Very low ASPECTS does not always mean uniformly dead tissue, and some patients may retain enough penumbral tissue to benefit from reperfusion. Conversely, some patients with deceptively higher scores may still do poorly if the infarct is strategically located or collaterals fail. This is why imaging must be interpreted in clinical context rather than in isolation.
Conclusion
The ancillary LASTE analysis provides persuasive evidence that EVT can improve functional outcomes and reduce mortality even in patients with the largest baseline infarcts, defined as ASPECTS 0-2, when treatment is delivered early in selected patients younger than 80 years. The findings support a shift away from using infarct size alone as a blanket exclusion criterion.
For clinicians, the practical message is nuanced: large core does not necessarily mean no benefit, but it does mean the conversation about benefit, hemorrhagic risk, and realistic recovery should be more explicit. For systems of care, the results reinforce the need for rapid imaging, efficient transfer pathways, and access to advanced stroke therapy even for patients who appear radiographically severe at presentation.
Further dedicated randomized trials, especially in older patients and CT-selected cohorts, will be important to define where the net benefit threshold truly lies. For now, LASTE adds important momentum to the growing view that even the biggest strokes may not be beyond the reach of thrombectomy.
Funding and ClinicalTrials.gov
ClinicalTrials.gov identifier: NCT03811769.
The abstract provided does not specify the funding source; readers should consult the full article for sponsor and support details.
References
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Note: Reference 5 is included as a topic placeholder in the abstract context and should be verified against the final published bibliography before use in formal citation lists.