Estimating the social value of mechanical thrombectomy randomized trials on an established stroke network

Given the relative strength of prior mechanical thrombectomy (MT) data in face of the perceived poor natural history of emergent large vessel occlusion strokes, randomization to medical therapy during the recent clinical MT trials raised ethical challenges at individual and institutional levels despite overall clinical equipoise.

In a thrombectomy stroke registry, we compared treatment rates preceding and following the SWIFT-PRIME and DAWN trials. Based on effect sizes of treatment in both trials, we estimated missed opportunities due to randomization to medical therapy and estimated the societal benefit resulting from additional patients who benefited as a result of these studies.

The average monthly thrombectomy rate in the SWIFT-PRIME time window increased from 14.1±4 patients-per-month (ppm) to 23.8±6 ppm (p<0·001). Twelve subjects were enrolled in SWIFT-PRIME and we estimated a missed opportunity of benefiting 2.3 of six subjects randomized to medical therapy. This was offset by providing treatment to an additional 9.7 ppm, resulting in an additional functional benefit to 3.7 ppm. Similarly, the thrombectomy rate in the DAWN window increased from 8.6±4 ppm pre-DAWN to 11.9±3.6 ppm post-DAWN (p<0.01). 38 subjects were enrolled in the DAWN trial with a missed opportunity to benefit eight of 16 subjects randomized to medical therapy. This was offset by the ability to offer MT to an additional 3.3 ppm, bringing definite benefit to an additional 1.65 ppm.

Completion of recent trials resulted in observable increases in rates of thrombectomy, translating to functional benefits that rapidly offset any missed opportunities due to randomization to medical therapy arms.