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Clinical Outcomes Similar for Patient Selection With Varying Noncontrast Imaging Methods

Data indicate that noncontrast CT may be an alternative to CTP or MRI for patients with proximal anterior circulation occlusion stroke who are candidates for mechanical thrombectomy.

A recent study found now significant differences in clinical outcomes for patients with late-presenting proximal anterior circulation occlusion stroke presenting in the extended time window selected for mechanical thrombectomy (MT) with noncontrast computed tomography (NCCT), compared with those selected with computed tomography perfusion (CTP) or MRI. Investigators suggest NCCT may be a simpler, less costly, easier-to-implement alternative for this patient population, potentially widening the indication for treating patients in the extended window. 

After 2304 patients were screened for eligibility, a total of 1604 patients with proximal anterior circulation stroke undergoing MT in the extended time window were included in the CT for Late Endovascular Reperfusion, or CLEAR, study (NCT04096248). Participants had a median age of 70 years (interquartile range, 59-80), and 848 were women (52.9%). Investigators, led by Thanh N. Nguyen, MD, FRCP, FSVIN, FAHA, director of interventional neurology/neuroradiology, Boston Medical Center; and professor of neurology, neurosurgery, and radiology, Boston University School of Medicine, found that 534 participants were selected to undergo MT by NCCT with angiography, 752 by CTP, and 318 by MRI. 

When investigating the primary end point of distribution of modified Rankin Scale (mRS) scores at 90 days after adjustment of cofounders, data showed no difference in shift between patients selected by CT compared with those selected by CTP (adjusted odds ratio [aOR], 0.95 [95% CI, 0.77-1.17]; P = .64), as well as those selected by CT compared with those selected by MRI (aOR, 0.95 [95% CI, 0.8-1.13]; P = .55). 

READ MORE: Mechanical Thrombectomy Shows Functional Benefit for Large Vessel Occlusion

“These findings have the potential to support the adoption of a more pragmatic selection of patients for MT in the extended window, simply based on NCCT and proximal anterior circulation large-vessel occlusion,” Nguyen et al wrote. “This selection could occur as an alternative to CTP-based or MRI-based selection paradigms, the second of which are not widely available across the globe, associated with potential treatment delays, cost, contrast load, radiation exposure, and resource use. On the other hand, it is important to note that management of patients in the NCCT group in the CLEAR study were not aligned with the American Stroke Association or European Stroke Organization guidelines.”

Similar rates of 90-day functional independence were identified for patients selected by CT vs CTP (aOR, 0.90 [95% CI, 0.7-1.16]; P = .42), but rates were lower in patients selected by MRI compared with those selected by CT (aOR, 0.79 [95% CI, 0.64-0.98]; P = .03). When compared with the MRI group, successful reperfusion was more common in the CT and CTP groups, reporting success with 250 cases (78.9%) vs 475 (88.9%) and 670 (89.5%), respectively (P <.001). Data suggested no significant differences in symptomatic intracranial hemorrhage between all 3 groups (CT, 42 [8.1%]; CTP, 43 [5.8%]; MRI, 15 [4.7%]; P = .11), nor with 90-day mortality (CT, 125 [23.4%]; CTP, 159 [21.1%]; MRI, 62 [19.5%]; P = .38). 

The multinational cohort study included data from 15 sites in 5 countries in Europe and North America. Included patients had proximal anterior circulation occlusion stroke presenting within 6 to 24 hours of time last seen well from January 2014 to December 2020, with follow-up duration spanning 90 days from stroke onset. Patients were excluded in the event of missing data to conduct a case analysis, with the final cohort of 1530 patients. 

Investigators noted limitations, including the study’s retrospective design, which may have led to selection bias and the inability to generalize results. The study was also limited to patients that fit inclusion criteria, meaning study findings cannot be applied to other patients. No independent imaging core laboratory was used in the study.

Nguyen TN, Abdalkader M, Nagel S, et al. Noncontrast computed tomography vs computed tomography perfusion or magnetic resonance imaging selection in late presentation of stroke with large-vessel occlusion. JAMA Neurol. Published online November 8, 2021. doi:10.1001/jamaneurol.2021.4082