Durability of the balloon-expandable covered versus bare-metal stents in the Covered versus Balloon Expandable Stent Trial (COBEST) for the treatment of aortoiliac occlusive disease Bibombe P. Mwipatayi, MMed (Surg), FCS (SA), FRACS, a,b Surabhi Sharma, MBBS, a Ali Daneshmand, MD, a Shannon D. Thomas, BMedSc, FRACS, c,d Vikram Vijayan, MRCS, FRCS, e Nishath Altaf, PhD, FRCS, a Marek Garbowski, MB BS, FRACS, f and Mark Jackson, MD, FRACS, g on behalf of the COBEST co-investigators,* Perth, Sydney, and Queensland, Australia; and Singapore Objective: The Covered vs Balloon Expandable Stent Trial (COBEST) is the first multicenter trial to investigate the patency of covered stents (CSs) and bare-metal stents (BMSs) in the treatment of aortoiliac arterial disease. The short-term results demonstrated that CSs were superior to BMSs in maintaining patency for TransAtlantic Inter-Society Consensus (TASC) C and D lesions at 18 months and were equivalent to BMSs for TASC B lesions. The current study was conducted to determine if the initial patency advantage of CSs over BMSs was sustained at the 5-year follow-up. Methods: A retrospective post hoc analysis of COBEST was performed. Originally, 125 patients with 168 iliac arteries were prospectively enrolled and randomly assigned to receive a CS or BMS. In this study, 77 of the 125 patients (61.6%; 119 limbs) were assessed at 60 months for the primary and secondary end points, with particular attention paid to the outcomes stratified according to TASC lesion severity. The primary end point was the rate of binary stenosis or freedom from stent occlusion of the treated area, as determined by ultrasound imaging or quantitative visual angiography. Results: The 5-year results of the COBEST showed that the CS had a significantly higher patency rate than the BMS at 18, 24, 48, and 60 months (95.1%, 82.1%, 79.9%, 74.7% for CS vs 73.9%, 70.9%, 63% and 62.5% for BMS; log-rank test, P [ .01). On multivariate analysis, the type of stent used (hazard ratio [HR], 2.797; 95% confidence interval [CI], 1.471- 5.318; P [ .002) and the Rutherford classification (HR, 2.019; 95% CI, 1.278-3.191; P [ .026) significantly affected the adjusted primary patency. On subgroup analysis, the CS showed significantly higher patency and a survival benefit compared with the BMS in TASC C and D lesions (HR, 8.639; 95% CI, 54.253-75.753; P [ .003). Moreover, fewer patients received target limb revascularization in the CS group than in the BMS group (odds ratio, 2.32; 95% CI, 1.47- 3.36; P [ .02); however, there was no statistically significant difference in the rate of amputations between the groups. Conclusions: The 5-year results of the COBEST demonstrated that the CS has an enduring patency advantage over the BMS in both the short and long terms. Furthermore, the CS showed acceptable patency rates for the treatment of more severe TASC C and D lesions, and patients who received a CS required fewer revascularization procedures. However, the choice of stent did not affect the rate of major limb amputations. (J Vasc Surg 2016;64:83-94.) Endovascular treatment is an efficacious, long-lasting, and safe option for the treatment of peripheral arterial occlusive disease in the iliac arteries, particularly TransAt- lantic Inter-Society Consensus (TASC) A and B lesions, with low complication rates and high patency rates. 1,2 During the last decade, advances in endovascular tech- niques and devices have allowed the treatment of more extensive and multifocal iliac lesions using endovascular procedures. 3,4 In 2007, the TASC classification was revised to TASC II, in which the adaptive range of lesion From the Department of Vascular Surgery, Royal Perth Hospital, a and the School of Surgery, Faculty of Medicine, Dentistry, and Health Sciences, University of Western Australia, b Perth; the University of New South Wales, c and the Prince of Wales Hospital, d Sydney; the Department of Vascular Surgery, Alexandra Hospital, Singapore e ; the Department of Vascular Surgery, Sir Charles Gairdner Hospital, Perth f ; and the Department of Vascular Surgery, Gold Coast Hospi- tal, Queensland. g *COBEST co-investigators: Dr Glen Benveniste, A/Prof Michael Denton, Dr John Anderson, Dr Steve Dubenec, Dr Michael Neale, Dr Vikram Puttaswamy, and Prof John Fletcher. Atrium Medical Corporation initially funded the study. However, the long- term follow-up of the patients was clinician driven, with no company or corporation funding involvement. The corresponding author had full ac- cess to all the data in the study, and the authors had final responsibility for the decision to submit for publication. Clinical Trial registration: ISRCTN89458845. Author conflict of interest: B.P.M. and M.J. have received research funding assistance from Atrium Medical Corporation. Presented at the Forty-first Veith Symposium, New York, NY, November 18-22, 2014; and the Royal Australasian College of Surgeons Annual Sci- entific Congress, Perth, Australia, May 4-8, 2015. Additional material for this article may be found online at www.jvascsurg.org. Correspondence: Bibombe P. Mwipatayi, MMed (Surg), FCS (SA), FRACS (Vasc), Department of Vascular Surgery, Royal Perth Hospital, Level 2, MRF Bldg, Rear 50 Murray St, Perth WA 6000 (e-mail: bibombe@ iinet.net.au; patrice.mwipatayi@uwa.edu.au). The editors and reviewers of this article have no relevant financial relationships to disclose per the JVS policy that requires reviewers to decline review of any manuscript for which they may have a conflict of interest. 0741-5214 Copyright Ó 2016 by the Society for Vascular Surgery. Published by Elsevier Inc. http://dx.doi.org/10.1016/j.jvs.2016.02.064 83