DISTAL at 12 Months: No Functional or Survival Advantage for Endovascular Therapy in Mild-to-Moderate Medium or Distal Vessel Occlusion Stroke

Highlights

DISTAL provides important long-term randomized evidence showing that, in patients with mild-to-moderate acute ischemic stroke due to medium or distal vessel occlusion, endovascular treatment added to best medical treatment did not improve 12-month functional outcome.

The distribution of disability at 12 months was similar in both groups, with an adjusted common odds ratio for better modified Rankin Scale outcome of 0.81 (95% CI 0.59-1.12; p=0.20).

Overall survival was also not significantly different between treatment strategies (hazard ratio 1.46, 95% CI 0.93-2.30; p=0.10), reinforcing the neutral signal seen at 90 days.

These findings do not support routine endovascular treatment for patients with predominantly mild-to-moderate medium or distal vessel occlusion stroke as enrolled in DISTAL.

Background and Clinical Context

Mechanical thrombectomy transformed the management of acute ischemic stroke caused by large vessel occlusion, producing substantial and reproducible gains in functional independence across multiple randomized trials. That success naturally led to broader interest in whether the same endovascular approach could help patients with more distal intracranial occlusions, including M2, M3, anterior cerebral artery, and posterior cerebral artery branch occlusions.

This question is clinically important. Medium or distal vessel occlusion strokes are common, often technically accessible, and can still produce disabling deficits despite relatively modest National Institutes of Health Stroke Scale (NIHSS) scores. However, the biological and procedural balance differs from proximal large vessel occlusion. Distal clots may be smaller, the ischemic core may evolve differently, spontaneous or thrombolysis-mediated recanalization may be more likely, and the target vessels are narrower and more fragile. As a result, procedural risk may be less forgiving, while the margin for benefit may also be smaller.

Before DISTAL, enthusiasm for thrombectomy in distal occlusions was driven largely by observational studies and extrapolation from large vessel occlusion trials. More recently, randomized evidence has been less supportive. The abstract of the present Lancet Neurology report notes that three of four randomized trials had already found no benefit of endovascular treatment over best medical treatment at 90 days. The 12-month DISTAL analysis therefore addresses an important gap: whether a delayed functional benefit, late recovery advantage, or survival difference might emerge beyond the conventional 90-day endpoint.

Study Design

Trial overview

DISTAL was a multicentre, open-label, randomized trial with blinded endpoint assessment. This design is appropriate for procedural stroke trials, where treatment allocation cannot realistically be masked to intervention teams, but outcome assessment can still be blinded to reduce ascertainment bias.

The trial was conducted at 55 hospitals in Europe and the Middle East and is registered on ClinicalTrials.gov as NCT05029414.

Population

Eligible participants were adults aged 18 years or older with acute ischemic stroke due to a medium or distal vessel occlusion. The occlusion sites included co-dominant or non-dominant M2 or M3-M4 middle cerebral artery branches, A1-A3 anterior cerebral artery segments, and P1-P3 posterior cerebral artery segments.

Patients presented either within 6 hours of last known well or between 6 and 24 hours if neuroimaging showed potentially salvageable tissue. This reflects contemporary imaging-guided triage and increases relevance to real-world stroke systems.

Randomization and treatment groups

Participants were randomly assigned in a 1:1 ratio via a centralized web-based system to either endovascular treatment plus best medical treatment or best medical treatment alone.

Best medical treatment could include intravenous thrombolysis when indicated. In fact, 355 of 543 analyzed patients, or 65%, received intravenous thrombolysis, indicating that reperfusion-focused medical therapy was commonly used and that the control arm was not undertreated.

Endpoints

The prespecified primary outcome for the 12-month analysis was disability measured using the ordinal modified Rankin Scale (mRS), with scores 5 and 6 combined, analyzed in the intention-to-treat population. The mRS remains the standard global disability outcome in stroke trials, and ordinal analysis is preferable to a dichotomized endpoint when treatment effects may be distributed across multiple disability levels.

The only safety outcome specified in this long-term analysis was overall survival.

Patient Characteristics

Between Dec 16, 2021, and July 10, 2024, 553 patients were enrolled. Ten later declined post-hoc consent, leaving 543 participants in the analysis. Of these, 239 patients (44%) were female and 304 (56%) were male. The median age was 77 years, with an interquartile range of 68 to 84 years, indicating an elderly stroke population typical of routine practice.

The cohort had generally mild-to-moderate neurological severity at presentation, with a median NIHSS score of 6 (IQR 5-9). This point is central to interpretation. Such patients can certainly remain disabled, but many also improve with time and supportive care, making it harder for an invasive strategy to demonstrate additional benefit unless the treatment effect is both real and clinically meaningful.

The distribution of occlusion sites was also informative. The predominant locations were M2 in 239 patients (44%), M3 in 146 (27%), P2 in 73 (13%), and P1 in 30 (6%). These are technically diverse lesions with potentially different natural histories, symptom profiles, and procedural challenges.

Randomization produced nearly equal groups: 271 patients were assigned to endovascular treatment plus best medical treatment and 272 to best medical treatment alone. Follow-up completeness was high, with 12-month data available for 524 patients (97%), which strengthens confidence in the long-term findings.

Key Findings

Primary functional outcome at 12 months

The primary finding was neutral. Median mRS at 12 months was 2 (IQR 1-4) in the endovascular treatment plus best medical treatment group and 2 (IQR 1-4) in the best medical treatment alone group. In the adjusted ordinal analysis, there was no significant difference in mRS distribution between groups. The adjusted common odds ratio for better functional outcome with endovascular treatment was 0.81 (95% CI 0.59-1.12; p=0.20).

Several aspects of this estimate deserve emphasis. First, the point estimate is below 1.0, which does not suggest even a directional trend toward benefit. Second, the confidence interval crosses 1 and includes the possibilities of modest harm or modest benefit, but the totality of the result is not supportive of routine thrombectomy in this population. Third, because the endpoint was ordinal rather than dichotomous, the analysis had the opportunity to detect a shift across the full disability spectrum; it still did not show advantage.

Survival

Overall survival also did not differ significantly between the two strategies. The hazard ratio was 1.46 (95% CI 0.93-2.30; p=0.10). Although not statistically significant, the point estimate again does not favor the endovascular approach. The confidence interval is wide enough that a modest excess mortality cannot be excluded, though the trial was not primarily powered for survival.

Relationship to the 90-day results

The authors state that the 12-month results are consistent with the previously reported 90-day results. This is clinically meaningful because one possible defense of neutral 90-day findings in stroke is that late neurological recovery, rehabilitation, or delayed cognitive improvement might reveal a longer-term advantage. DISTAL does not support that argument. The absence of a signal at 12 months suggests the neutral short-term result was not simply due to premature outcome assessment.

Clinical Interpretation

The practical message is straightforward: for the type of patients enrolled in DISTAL, routine endovascular treatment should not be considered standard care solely on the basis of having a medium or distal vessel occlusion.

This conclusion is especially relevant because distal thrombectomy can appear intuitively attractive. The clot is visible, devices are increasingly sophisticated, and procedural success may seem achievable in experienced hands. Yet technical feasibility is not equivalent to net clinical benefit. DISTAL underscores that the benefit-risk equation in smaller intracranial arteries is fundamentally different from that in internal carotid or proximal middle cerebral artery occlusions.

Several factors likely contribute to the neutral result. First, baseline stroke severity was modest. A median NIHSS of 6 indicates that many patients may recover reasonably well with best medical therapy alone, reducing absolute room for improvement. Second, intravenous thrombolysis was used frequently, which may have attenuated any incremental benefit of intervention by promoting recanalization or improving distal perfusion. Third, distal vessel access and clot retrieval may carry procedural costs, including endothelial injury, perforation risk, vasospasm, distal embolization, or time delays, even when major complications are uncommon. Finally, the enrolled population was heterogeneous with respect to territory and vessel caliber, and a true benefit in a very narrow subgroup could have been diluted in the overall analysis.

How DISTAL Fits Into the Evolving Evidence Base

DISTAL adds to a growing body of randomized evidence challenging the assumption that thrombectomy benefit extends seamlessly from proximal large vessel occlusion to more distal targets. The abstract explicitly notes that three of four randomized trials had reported no benefit at 90 days. This cumulative signal matters more than any single study. When multiple randomized datasets point in the same direction, continued routine use becomes harder to justify outside carefully selected circumstances.

At the same time, DISTAL should not be misread as proving that thrombectomy can never help a patient with distal occlusion. Rather, it shows that a broad treatment policy for patients resembling those enrolled in the trial is unsupported. Future research may still identify subgroups more likely to benefit, such as patients with clearly disabling deficits despite low NIHSS, proximal M2 occlusions with substantial perfusion mismatch, eloquent-territory ischemia, poor collateral profiles, or failure of early reperfusion after thrombolysis. However, those hypotheses require prospective validation rather than procedural optimism.

Strengths of the Trial

DISTAL has several notable strengths. It was randomized and multicentre, increasing internal validity and generalizability across different healthcare systems. Endpoint assessment was blinded, reducing bias in disability evaluation. Follow-up was excellent at 97% for the 12-month analysis, which is especially valuable in elderly stroke populations. The use of ordinal mRS analysis is methodologically sound and more informative than a simple independent-versus-dependent dichotomy.

Another strength is the contemporary medical management context. Because many patients received intravenous thrombolysis and were treated within modern stroke pathways, the comparison more closely reflects actual current practice than older historical control frameworks.

Limitations and Remaining Questions

Several limitations should temper overgeneralization. First, the trial was open-label, which is unavoidable in procedural trials but still introduces potential for performance differences outside blinded endpoint assessment. Second, the population mainly had mild-to-moderate stroke severity, so the conclusions are strongest for that clinical profile rather than for more severe distal occlusion syndromes.

Third, medium and distal vessel occlusion is not a single disease entity. M2, M3, ACA, and PCA occlusions differ in symptoms, eloquence, infarct pattern, and technical accessibility. Although combining them is practical for trial enrollment, this heterogeneity may obscure differential treatment effects. Fourth, the abstract does not provide detailed subgroup analyses, reperfusion metrics, or procedural complication breakdown for the 12-month report, limiting deeper mechanistic interpretation from the data presented here alone.

Fifth, because overall survival was the only safety outcome highlighted in this long-term analysis, readers should not assume the absence of all procedural harms; rather, those details likely remain in the main 90-day and procedural datasets. Finally, while the confidence intervals do not support benefit overall, they do not fully exclude the possibility of narrowly defined responders, which remains a research priority.

Implications for Practice and Policy

For clinicians, DISTAL argues for restraint. In patients with mild-to-moderate stroke due to medium or distal vessel occlusion, best medical treatment remains the evidence-supported default. Endovascular therapy should not be routinely pursued simply because the lesion is technically reachable.

For stroke centers and policymakers, the findings are also relevant to systems-of-care design. Expanding thrombectomy pathways to increasingly distal occlusions has logistical, staffing, and cost implications. Neutral randomized evidence at both 90 days and 12 months suggests that indiscriminate broadening of thrombectomy indications would risk adding procedural burden without clear patient benefit.

For investigators, the next phase should focus on precision selection rather than blanket adoption. Trials enriched for disabling symptoms, advanced perfusion mismatch, high-risk eloquent territories, or specific vessel segments may be more productive than repeating broad all-comer designs.

Conclusion

The 12-month DISTAL results are clinically important because they answer a question that shorter follow-up could not fully resolve. In adults with acute ischemic stroke caused by medium or distal vessel occlusion, endovascular treatment plus best medical treatment did not reduce long-term disability or improve survival compared with best medical treatment alone. The neutral long-term findings align with the 90-day data and do not support routine thrombectomy for the predominantly mild-to-moderate patient population enrolled in this study.

In stroke medicine, successful translation from proximal large vessel occlusion to more distal disease cannot be assumed. DISTAL reminds the field that randomized evidence, not technical capability alone, must determine standards of care.

Funding and Trial Registration

Funding: Swiss National Science Foundation, Gottfried und Julia Bangerter-Rhyner-Foundation, Medtronic, Stryker Neurovascular, Phenox, Rapid Medical, and Penumbra.

ClinicalTrials.gov: NCT05029414.

References

Fischer U, Brehm A, Ribo M, Rizzo F, Strbian D, Räty S, Arenillas JF, Martínez-Galdámez M, Hajdu SD, Michel P, Gralla J, Piechowiak EI, Kaiser DPO, Puetz V, Van den Bergh F, De Raedt S, Bellante F, Dusart A, Hellstern V, Khanafer A, Parrilla G, Morales A, Kirschke JS, Wunderlich S, Fiehler J, Thomalla G, Lemmens R, Peluso JP, Bolognese M, von Hessling A, van Es A, Kruyt ND, Coutinho JM, Castaño C, Minnerup J, van Zwam W, Dhondt E, Nolte CH, Machi P, Loehr C, Mattle HP, Buhk JH, Kaesmacher J, Dobrocky T, Papanagiotou P, Alonso A, Holtmannspoetter M, Zini A, Renieri L, Keil F, van den Wijngaard I, Kägi G, Terceño M, Wiesmann M, Amaro S, Fragata I, Katan M, Leker RR, Saver JL, Staals J, Rommers N, Balmer L, Psychogios M, DISTAL investigators. Endovascular treatment for medium or distal vessel occlusion stroke (DISTAL): 12-month outcomes of a multicentre, open-label, randomised trial. The Lancet. Neurology. 2026-05-06. PMID: 42105785.

ClinicalTrials.gov. DISTAL: Endovascular Treatment Plus Best Medical Treatment Versus Best Medical Treatment Alone in Acute Ischemic Stroke Due to Medium or Distal Vessel Occlusion. NCT05029414.