Boers AMM, et al. - In this pooled data mediation analysis of randomized clinical trials with 1,665 patients with acute ischemic stroke, researchers studied whether follow-up infarct volume (FIV) impacts the relationship between endovascular therapy (EVT) and functional outcome. Findings revealed that the reduction in follow-up infarct volume was a predictor of functional outcome, but only 12% of the benefit of endovascular therapy was explained. In phase 2 and 3 trials of acute ischemic stroke, follow-up infarct volume as measured on computed tomography and magnetic resonance imaging is not a valid proxy for estimating treatment effect.