• Richard Bulbulia and Alison Halliday.
• Medical Research Council Population Health Research Unit, Clinical Trial Service Unit and Epidemiological Studies Unit, Nuffield Department of Population Health, University of Oxford, Oxford, UK.
• Health Technol Assess. 2017 Oct 1; 21 (57): 1-40.

BackgroundA successful open surgical operation to remove atheromatous carotid artery narrowing that has not yet caused a stroke (asymptomatic carotid stenosis) carries some procedural risk but, if completed successfully, halves patients' future annual stroke risk for at least 10 years. A newer, less invasive alternative is carotid stenting, which also carries some procedural risk, especially if the carotid lesion has recently given rise to a stroke (symptomatic carotid stenosis). For both surgery and stenting, improvements in technique (and in medication) have reduced risk. Early studies showed that treating carotid narrowing by stenting, particularly for symptomatic lesions, caused more procedural minor strokes than surgery, but more recent trials in symptomatic and in asymptomatic patients found that both procedures might now be equally safe and effective. However, low patient numbers, short follow-up of the long-term effects on stroke rates and wide confidence intervals mean that worldwide uncertainty persists between carotid surgery and carotid stenting, and national and international guidelines remain unclear as to which is generally better.ObjectivesThe second Asymptomatic Carotid Surgery Trial (ACST-2) compares carotid endarterectomy (CEA) with carotid artery stenting (CAS) directly, randomising patients with asymptomatic carotid stenosis for whom a carotid procedure is considered definitely necessary; both procedures seem anatomically feasible, and there is substantial uncertainty as to which of the two would be better for such individuals. Although it will compare procedural risks, the trial's primary aim is to compare the long-term durability of protection against strokes occurring in the years post procedure due to any remaining or recurrent carotid disease.DesignRandomised controlled trial comparing CEA with CAS.SettingHospitals in the UK and worldwide, in which carotid procedures are common.ParticipantsMen and women with severely stenotic atherosclerotic carotid artery disease, with or without previous stroke but with no recent symptoms from the randomised artery.InterventionsCEA and CAS.Outcomes(1) Periprocedural risk defined as myocardial infarction, stroke or death within 30 days after the randomised procedure and (2) long-term rates of disabling or fatal stroke during follow-up of patients.Measurement Of Costs And OutcomesMeasurement of intervention costs and stroke costs (periprocedural and during follow-up) and of quality of life [EuroQol-5 Dimensions (EQ-5D®)] for patients in the top six recruiting countries (UK, Italy, Belgium, Germany, Serbia and Sweden), who currently constitute 85% of those randomised.Progress So FarBy the end of March 2016, ACST-2 had included 2125 patients, nearly two-thirds of the planned recruitment of 3600; 1061 were randomly allocated to CEA and 1064 to CAS.ConclusionsFurther funding has been secured and recruitment continues, with completion anticipated by the end of 2019. ACST-2 will report initial results in 2021.Trial RegistrationCurrent Controlled Trials ISRCTN21144362.FundingThis project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 21, No. 57. See the NIHR Journals Library website for further project information. Funding was also received from BUPA Foundation [BUPAF/33(a)/05].

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