BACKGROUND AND OBJECTIVES: The management of anterior circulation tandem lesion stroke remains controversial, given its under-representation in randomized thrombectomy trials and uncertainty regarding optimal extracranial carotid intervention. We aimed to determine whether emergent carotid stenting (eCAS) during endovascular thrombectomy (EVT) for anterior circulation tandem lesions improves 90-day functional outcomes compared with a no-stenting strategy.

METHODS: We conducted an international multicenter longitudinal retrospective cohort study (CERES-TANDEM, NCT06965036) of consecutive adults treated at 49 comprehensive stroke centers in Europe, North America, and Singapore for anterior circulation acute ischemic stroke due to tandem lesions from January 1, 2018, to December 31, 2024. Exclusion criteria were primary hemorrhagic stroke, absence of intracranial occlusion, presentation >24 hours from symptom onset, and age younger than 18 years. We compared 90-day modified Rankin Scale (mRS) scores between participants receiving eCAS and those receiving no stenting during EVT. The primary estimand was mRS shift, analyzed by stabilized inverse probability of treatment weighting (IPTW)-weighted ordinal regression. Additional estimands were direct-effect estimand adjusting for successful recanalization (defined as Thrombolysis in Cerebral Infarction grade 2b or higher) and symptomatic intracranial hemorrhage (sICH) (estimand 2) and stratum estimand restricting to never-crossers (estimand 3).

RESULTS: Of 4,053 patients (mean age 70 years, 65.5% female), 2,522 underwent eCAS and 1,531 received no stenting. After IPTW, eCAS was associated with an improved 90-day functional outcome (common odds ratio (OR) 1.31; 95% CI 1.17-1.47;p < 0.001) and higher odds of mRS score 0-1 (OR 1.27; 95% CI 1.08-1.50; p = 0.005) and mRS score 0-2 (OR 1.30; 95% CI 1.13-1.51; p < 0.001), without a significant increase in sICH (OR 1.21; 95% CI 0.93-1.56; p = 0.15). Findings were consistent in direct-effect (common OR 1.17; 95% CI 1.04-1.31; p = 0.008) and stratum (common OR 1.37; 95% CI 1.21-1.55; p < 0.001) estimands. There was no interaction for intracranial occlusion site, IV thrombolysis, sedation technique, EVT approach, or access site. Sensitivity analysis including recanalization in IPTW-weighted estimand 1 framework confirmed the association of eCAS with improved 90-day functional outcomes (common OR 1.14, 95% CI1.02-1.27, p = 0.008).

DISCUSSION: In this large real-world cohort, eCAS during EVT for anterior circulation tandem lesions was associated with superior 90-day functional recovery without increased hemorrhagic risk. These findings support consideration of eCAS in clinical practice and warrant confirmation in randomized trials.

TRIAL REGISTRATION INFORMATION: Registered in clinicaltrials.gov, NCT06965036.

CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that in patients with stroke due to anterior circulation tandem lesions, eCAS during EVT improves 90-day functional outcomes compared with EVT alone.