ABSTRACT NUMBER: ESOC2026A1066 AUTOMATED ASSESSMENT OF COLLATERAL STATUS IN MEDIUM OR DISTAL VESSEL OCCLUSION STROKE: A DISTAL SUBSTUDY

Abstract Background and aims The DISTAL trial compared endovascular treatment (EVT) plus best medical treatment (BMT) to BMT alone in acute ischemic stroke patients with medium or distal vessel occlusions (MDVOs). The trial was neutral, leaving EVT-use in MDVOs individualized and selection criteria unclear. Collateral status modifies EVT-effect in large vessel occlusions. Traditional, visual collateral scoring overestimates collateral status in MDVOs. Therefore, we applied an automated Occlusion-Downstream Area Collateral Score (ODACS), assessing collaterals within the downstream area, and investigated whether ODACS modifies treatment effect. Methods We included patients from the DISTAL trial with MDVO in the middle cerebral artery and baseline CT, CTA, and CTP. Collaterals were quantified using ODACS, derived from CTA-based vessel segmentation and CTP hypoperfusion maps, and categorized into four collateral grades (CS0-CS3) based on arterial filling relative to the contralateral side (Figure 1). The primary outcome was 90-day modified Rankin Scale (mRS). Treatment effect was analyzed using ordinal regression with interaction terms to assess modification by collateral status. Results We included 253 patients and found a non-linear interaction between collateral status and treatment effect on 90-day mRS. Patients with absent collaterals (CS0) had worse outcomes with EVT plus BMT (cOR0.08;95%-CI0.02-0.42) compared to BMT alone. Those with excellent collaterals (CS3) showed a trend towards worse outcomes with EVT (cOR0.47;95%-CI0.20-1.08). Intermediate grades (CS1/CS2) demonstrated neutral effects. Conclusions In the DISTAL cohort, collateral status modified EVT-effect in MDVOs. No subgroup showed EVT benefit, while patients with absent, and to a lesser degree, excellent collaterals suggested risk of harm with EVT. Conflict of interest SD, LdV, AvE, NR, VA: Nothing to disclose; WvZ discloses grants from Bayer Healthcare Pharmaceuticals Inc. and is consultant for Johnson&Johnson International, Stryker and Philips; JS discloses speaker fees from Medtronic; HM is confounder and shareholder of Nicolab, TrainecT and inSteps; MP discloses unrestricted grants from Swiss National Science Foundation (SNF), Bangerter-Rhyner Stiftung, Stryker Neurovascular Inc., Phenox GmbH, Medtronic Inc., Rapid Medical Inc., and Penumbra Inc for the DISTAL trial, grant for SPINNERS trial from Siemens Healthineers AG (money paid to institution) and the following speaker fees: Stryker Neurovascular Inc., Medtronic Inc., Penumbra Inc., Acandis GmbH, Phenox GmbH, Rapid Medical Inc. and Siemens Healthineers AG (money paid to institution); UF reports research support of the Swiss National Science Foundation and the State Secretariat for Education, Research and Innovation; research support of the Swiss Heart Foundation, the Swiss Brain League and the Horton Foundation; research grants from Medtronic and from Stryker, Rapid medical, Penumbra, Medtronic and Phenox, Boehringer Ingelheim; consultancies for Medtronic, Bayer, Boehringer Ingelheim, Boston Scientific, CSL Behring, Merck, Siemens and Takeda (fees paid to institution). Participation in an advisory board for AstraZeneca (former Alexion/Portola), Auzone, Biogen, AbbVie, Siemens, Corxel (fees paid to institution). Member of a clinical event committee (CEC) of the COATING study (Phenox). Member of the data and safety monitoring committee (DSMB) of the TITAN, RESCIND, LATE_MT, IN EXTREMIS and RapidPulse trials. Past president of the Swiss Neurological Society and president-elect of the European Stroke Organisation. Figure 1 - belongs to Methods