Vein bypass first vs. best endovascular treatment first revascularisation strategy for chronic limb-threatening ischaemia due to infra-popliteal disease: the BASIL-2 RCT.

Background: Chronic limb-threatening ischaemia with ischaemic pain and/or tissue loss.

Objective: To examine the clinical and cost-effectiveness of a vein bypass-first compared to a best endovascular treatment-first revascularisation strategy in preventing major amputation or death.

Design: Superiority, open, pragmatic, multicentre, phase III randomised trial.

Setting: Thirty-nine vascular surgery units in the United Kingdom, and one each in Sweden and Denmark.

Participants: Patients with chronic limb-threatening ischaemia due to atherosclerotic peripheral arterial disease who required an infra-popliteal revascularisation, with or without an additional more proximal infra-inguinal revascularisation procedure, to restore limb perfusion.

Interventions: A vein bypass-first or a best endovascular treatment-first infra-popliteal, with or without an additional more proximal infra-inguinal revascularisation strategy.

Main outcome measures: The primary outcome was amputation-free survival. Secondary outcomes included overall survival, major amputation, further revascularisation interventions, major adverse limb event, health-related quality of life and serious adverse events.

Methods: Participants were randomised to a vein bypass-first or a best endovascular treatment-first revascularisation strategy. The original sample size of 600 participants (247 events) was based on a hazard ratio of 0.66 with amputation-free survival rates of 0.72, 0.62, 0.53, 0.47 and 0.35 in years 1-5 in the best endovascular treatment-first group with 90% power and alpha at p = 0.05. The sample size was revised to an event-based approach as a result of increased follow-up time due to slower than anticipated recruitment rates. Participants were followed up for a minimum of 2 years. A cost-effectiveness analysis was employed to estimate differences in total hospital costs and amputation-free survival between the groups. Additionally, a cost-utility analysis was carried out and the total cost and quality-adjusted life-years, 2 and 3 years after randomisation were used.

Results: Between 22 July 2014 and 30 November 2020, 345 participants were randomised, 172 to vein bypass-first and 173 to best endovascular treatment-first. Non-amputation-free survival occurred in 108 (63%) of 172 patients in the vein bypass-first group and 92 (53%) of 173 patients in the best endovascular treatment-first group [adjusted hazard ratio 1.35 (95% confidence interval 1.02 to 1.80); p = 0.037]. Ninety-one (53%) of 172 patients in the vein bypass-first group and 77 (45%) of 173 patients in the best endovascular treatment-first group died [adjusted hazard ratio 1.37 (95% confidence interval 1.00 to 1.87)]. Over follow-up, the economic evaluation discounted results showed that best endovascular treatment-first was associated with £1690 less hospital costs compared to vein bypass-first. The cost utility analysis showed that compared to vein bypass-first, best endovascular treatment-first was associated with £224 and £2233 less discounted hospital costs and 0.016 and 0.085 discounted quality-adjusted life-year gain after 2 and 3 years from randomisation.

Limitations: Recruiting patients to the Bypass versus Angioplasty in Severe Ischaemia of the Leg Trial-2 trial was difficult and the target number of events was not achieved.

Conclusions: A best endovascular treatment-first revascularisation strategy was associated with better amputation-free survival, which was largely driven by fewer deaths. Overall, the economic evaluation results suggest that best endovascular treatment-first dominates vein bypass-first in the cost-effectiveness analysis and cost-utility analysis as it was less costly and more effective than a vein bypass-first strategy.

Future work: The Bypass versus Angioplasty in Severe Ischaemia of the Leg Trial-2 investigators have a data sharing agreement with the BEst Surgical Therapy in patients with Chronic Limb threatening Ischaemia investigators. One output of this collaboration will be an individual patient data meta-analysis.

Study registration: Current Controlled Trials ISRCTN27728689.

Funding: This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (NIHR award ref: 12/35/45) and is published in full in Health Technology Assessment; Vol. 28, No. 65. See the NIHR Funding and Awards website for further award information.