Objective:To investgate the effect of endovascular therapy (EVT) on the requirement for decompressive craniectomy (DC) and functional outcomes in patients with large anterior circulation ischemic stroke.Methods:Patients with large anterior circulation ischemic stroke within 24 hours of onset admitted to the Department of Neurology, West China Hospital, Sichuan University between September 2017 and December 2019 were included. Outcome indicators included DC demand and poor outcome at 3 months. The latter was defined as a modified Rankin Scale score >2. Multivariate logistic regression analysis was used to determine independent factors of DC requirement and functional outcomes at 3 months. Results:A total of 381 patients with large anterior circulation ischemic stroke were enrolled, including 203 males (53.3%), and the mean age was 70.7±14.3 years. The median time from onset to admission was 4.5 hours. The median baseline National Institutes of Health Stroke Scale score was 17 and median baseline Alberta Stroke Program Early Computed Tomography Score (ASPECTS) was 7. Totally 139 patients (36.5%) received EVT, and 64 (16.8%) required DC; 376 patients (98.7%) completed a 3-month follow-up (5 who did not complete follow-up did not require DC, of which 2 received EVT), 312 (83.0%) had poor outcome at 3 months, and 146 (38.8%) died. Multivariate logistic regression analysis showed that EVT was an independent predictor for the requiremet of DC (odds ratio [ OR] 4.42, 95% confidence interval [ CI] 1.81-10.81; P=0.001), higher baseline ASPECTS ( OR 0.80, 95% CI 0.71-0.89; P<0.001) and successful recanalization ( OR 0.37, 95% CI 0.15-0.90; P=0.028) were independent protective factors of reducing the requirement of DC. Successful recanalization ( OR 0.09, 95% CI 0.01-0.72; P=0.023) and antiplatelet therapy ( OR 0.29, 95% CI 0.11-0.76; P=0.012) were independent predictors for reduced risk of poor outcome. In 139 patients who received EVT, 27 (19.4%) received intravenous thrombolysis, 96 (69.1%) achieved successful recanalization, 88 (63.3%) had hemorrhagic transformation, 61 (43.9%) had symptomatic hemorrhagic transformation, and 34 (24.5%) required DC; 137 (98.6%) completed a 3-month follow-up, 116 (84.7%) had poor outcome at 3 months, and 67 (48.9%) died. For patients receiving EVT, a higher baseline ASPECTS ( OR 0.72, 95% CI 0.60-0.88; P=0.001) and successful recanalization ( OR 0.35, 95% CI 0.14-0.90; P=0.029) were independent predictors of reducing the requirement of DC, while successful recanalization ( OR 0.09, 95% CI 0.01-0.71; P=0.022) was an independent predictor for reduced risk of poor outcome. Among 64 patients who required DC, 22 (34.4%) received DC. Receiving DC significantly reduced the mortality within 3 months ( OR 0.25, 95% CI 0.07-0.86; P=0.028), but had no significant effect on functional outcome at 3 months ( OR 0.35, 95% CI 0.03-4.38; P=0.412). There was no significant interaction of either EVT or successful recanalization in the effect of DC on 3-month death ( P for interaction > 0.05). Conclusions:Successful recanalization after EVT reduces requirement for DC in patients with large anterior circulation ischemic stroke and improves functional outcome at 3 months. DC can reduce the mortality in patients required DC, and have no interactive effect with EVT or successful recanalization.