Efficacy and safety of flow diverter therapy for unruptured intracranial aneurysms compared to conventional endovascular therapy: a multicentre, randomised, open-label trial in South Korea.

Background: Endovascular coil embolisation is widely used for unruptured intracranial aneurysms (UIAs), but incomplete occlusion and recurrence remain concerns for aneurysms ≥7 mm. Flow diverters were developed to improve outcomes in larger aneurysms; however, randomised comparisons with conventional endovascular therapy are limited. We compared the efficacy and safety of flow diversion vs. conventional endovascular therapy in patients with UIAs measuring ≥7 mm or recurrent aneurysms after initial endovascular treatment. Methods: In this multicentre, randomised, open-label trial at 13 tertiary institutions in South Korea, patients with unruptured or recurrent intracranial aneurysms were randomly assigned (1:1) to flow diversion or conventional endovascular therapy. Eligible patients were aged 19-75 years of age with UIAs ≥7 mm in maximum diameter or with recurrent aneurysms after initial endovascular treatment. Recurrent aneurysms were defined as grade 2 (70-89% occlusion) or higher. The primary endpoint was complete or near-complete aneurysm occlusion at 12 months (grade 0 or 1). Secondary endpoints included procedure-related complications, thromboembolic or haemorrhagic events, and neurological outcomes. Intention-to-treat analyses were performed. Missing outcome data were handled using multiple imputation under the missing-at-random assumption. The trial was registered with the Clinical Research Information Service (KCT0006474). Findings: Between Jan 1, 2022, and Dec 31, 2023, of 168 screened patients, 160 were randomised (80 per group). Two patients in each group withdrew before treatment; two in the conventional therapy group crossed over to flow diversion. At 12 months, complete aneurysm occlusion was achieved in 96.3% of conventional therapy patients vs. 75.0% of flow diversion patients (adjusted odds ratio 6.46, 95% CI 1.94-29.98; p = 0.006). Procedure-related complications occurred in one (1.3%) patient in the conventional therapy and two (2.5%) in the flow diversion group (p = 0.347). Thromboembolic events occurred in two (2.5%) and four (5.0%) patients, respectively (p = 0.274). Haemorrhagic events and neurological outcomes were similar between groups. Interpretation: Conventional endovascular therapy resulted in higher rates of complete aneurysm occlusion at 12 months, without increased procedural or neurological risk. These findings emphasise the importance of patient and device selection and suggest that conventional endovascular therapy remains a robust first-line option for selected patients with intracranial aneurysms ≥7 mm. Long-term follow-up is required to assess the durability of flow diversion. Funding: Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Korean Ministry of Health and Welfare.