Health Technology Assessment (Oct 2024)
Vein bypass first vs. best endovascular treatment first revascularisation strategy for chronic limb-threatening ischaemia due to infra-popliteal disease: the BASIL-2 RCT
Abstract
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. Plain language summary Atherosclerosis, or narrowing of the arteries, can occur as a result of smoking, high blood pressure, diabetes, or high cholesterol in the blood. Atherosclerosis can affect any artery, including those supplying the legs, where the condition is called peripheral arterial disease. The most severe form of peripheral arterial disease is chronic limb-threatening ischaemia which can cause severe pain in the foot as well as ulcers and gangrene. Unless the blood supply to the leg and foot is improved, by a process called revascularisation, people with chronic limb-threatening ischaemia are at high risk of amputation and death. The blood supply can be improved by using a vein from the leg to bypass around the blockages (vein bypass) or by using a balloon (angioplasty) or small metal tubes (stents) to reopen the blocked arteries (best endovascular treatment). There is debate about which type of revascularisation is best in terms of preventing amputation and death, especially in people who need revascularisation of the arteries below the knee. Bypass versus Angioplasty in Severe Ischaemia of the Leg Trial-2 is the first randomised controlled trial to compare vein bypass-first and best endovascular treatment-first in this group of patients. Bypass versus Angioplasty in Severe Ischaemia of the Leg Trial-2 found that people randomised to a vein bypass-first revascularisation strategy were 35% more likely to require a major amputation or die than those randomised to a best endovascular treatment-first strategy. Most of this difference in favour of best endovascular treatment-first was due to a higher number of patients dying in the vein bypass-first group. Best endovascular treatment-first was also cheaper for the National Health Service. The results of this study suggest that in patients with chronic limb-threatening ischaemia due to peripheral arterial disease in the arteries below the knee, who are suitable for both vein bypass and best endovascular treatment and where there is uncertainty as to which is best, best endovascular treatment should be offered first rather than vein bypass. Scientific summary Background Chronic limb-threatening ischaemia (CLTI) is the severest manifestation of peripheral arterial disease (PAD) and presents with ischaemic pain at rest or tissue loss (ulceration, gangrene or both) or both. The researchers compared the effectiveness of a vein bypass (VB)-first with a best endovascular treatment (BET)-first revascularisation strategy in terms of preventing major amputation and death in patients with CLTI who required an infra-popliteal (IP) revascularisation, with or without an additional more proximal infra-inguinal revascularisation procedure, to restore limb perfusion. Objectives The primary objective of the study was to examine the effectiveness and cost-effectiveness of using a VB-first compared to a BET-first revascularisation strategy in terms of preventing major (above the ankle) amputation or death from any cause [amputation-free survival (AFS)] in patients with CLTI who required an IP, with or without an additional more proximal infra-inguinal revascularisation procedure, to restore limb perfusion. Design Superiority, open-label, pragmatic, multicentre, phase III randomised trial. Setting Thirty-nine vascular surgery units in the United Kingdom, and one each in Sweden and Denmark. Participants Those with CLTI due to atherosclerotic PAD and who required an IP revascularisation, with or without an additional more proximal infra-inguinal revascularisation procedure, to restore limb perfusion. Interventions A VB-first or a BET-first IP, with or without an additional more proximal infra-inguinal revascularisation strategy, to restore limb perfusion. Most VBs were constructed with great saphenous vein and originated from the common or superficial femoral arteries. Most endovascular interventions comprised plain balloon angioplasty with selective use of plain or drug-eluting stents. Outcome measures The primary outcome was AFS defined as time to first major (above the ankle) amputation or death from any cause. Secondary outcomes included: time to death from any cause (overall survival); time to major amputation of the trial leg; major adverse limb event (defined as major amputation of the trial leg, or any further major revascularisation intervention to the trial leg, following the first revascularisation intervention); major adverse cardiac event (defined as chronic limb-threatening ischaemia and/or major amputation affecting the non-trial leg, myocardial infarction, transient ischaemic attack or stroke); 30-day morbidity and mortality; relief of ischaemic pain as determined by visual analogue scale and opiate usage; health- related quality of life using generic [EuroQol-5 Dimensions, five-level version (EQ-5D-5L), Short Form questionnaire-12 items, ICEpop CAPability measure for Older people] and disease-specific (the Vascular Quality of Life Questionnaire) tools; further major revascularisation intervention to the trial leg (following the first revascularisation intervention); re-intervention and crossover intervention (where re-intervention is defined as the same, and a crossover procedure is defined as an alternative, revascularisation procedure to the first revascularisation procedure post-randomisation); healing of tissue loss (ulcers, gangrene) at or below the ankle presumed to be caused by PAD as assessed by the perfusion, extent, depth, infection and sensation score, the Wound Ischaemia and foot Infection tool; and haemodynamic measurements (ankle–brachial pressure index, and toe brachial pressure index). Serious adverse events were collected up to 30 days post first revascularisation. Economic evaluation analyses in the form of cost-effectiveness and cost–utility analysis (CUA) were conducted from the perspective of the UK NHS alongside the trial. The base case analyses considered only hospital costs and an additional scenario and subgroup analyses were carried out. Sample size The original sample size was based on a time-to-event analysis to be undertaken 2 years after completion of recruitment. It was anticipated that recruitment would take place over 3 years: 20% of patients recruited in year 1, 40% in year 2 and 40% in year 3. Based on the Bypass versus Angioplasty in Severe Ischaemia of the Leg Trial (BASIL-1) trial. AFS rates were assumed to be 0.72 in year 1, 0.62 in year 2, 0.53 in year 3, 0.47 in year 4 and 0.35 in year 5. Allowing for a 10% attrition rate and based on the survival estimates calculated using the BASIL-1 data, a population of 600 participants (247 primary outcome events) would have 90% power to detect a reduction in AFS of one-third [hazard ratio (HR) 0.66] at the 5% significance level. The initial assumptions made in this trial concerning recruitment rates were not achieved; therefore, recruitment continued beyond year 3. As a result, the median length of follow-up was longer than originally planned. Therefore, the number of randomised participants required to observe 247 events (as per the original sample size target) was reduced due to the increased exposure time. With support of the funder and independent oversight from the Data Monitoring Committee, recruitment rates, length of follow-up, and pooled event rates over time were modelled to predict the number of participants needed to reach 247 events, with 24 months minimum follow-up in each participant. The modelling was updated approximately every 6 months based on emerging data. Results Between 22 July 2014 and 30 November 2020, 345 participants were randomised, 172 to the VB-first group and 173 to the BET-first group. The baseline characteristics of the two groups were similar. Major amputation or death occurred in 108 (63%) of 172 patients in the VB-first group and 92 (53%) of 173 patients in the BET-first group {adjusted HR 1.35 [95% confidence interval (CI) 1.02 to 1.80]; p = 0.037}. Ninety-one (53%) of 172 patients in the VB-first group and 77 (45%) of 173 patients in the BET-first group died [adjusted HR 1.37 (95% CI 1.00 to 1.87)]. In both groups the commonest causes of morbidity and mortality, including those occurring within 30 days of their first revascularisation, were cardiovascular and respiratory events. Over follow-up, the economic evaluation results showed that BET-first was associated with £1690 less hospital costs compared to VB-first with additional survival without amputation. The cost utility analysis showed that compared to VB-first, BET-first was associated with £2524 and £2233 less hospital costs and 0.016 and 0.085 QALY gain after 2 and 3 years from randomisation. Conclusions In the BASIL-2 trial, a BET-first revascularisation strategy was associated with a better AFS, which was largely driven by fewer deaths in the BET-first group. In both the CUA and cost-effectiveness analysis (CEA) analyses and from a NHS and societal perspective BET-first dominated VB-first and is therefore a highly cost-effective intervention for the NHS. These data suggest a greater role for BET in the management of patients with CLTI who require an IP revascularisation to restore limb perfusion. In patients with CLTI who required an IP, with or without an additional more proximal infra-inguinal revascularisation procedure, to restore limb perfusion, a BET-first revascularisation strategy was associated with reduced hospital costs (£1690) and improved AFS (0.429 years), out to 7 years following randomisation. BET-first therefore dominated VB-first in the CEA. Similarly, in the health-related quality of life the CUA, BET-first was cost-saving with improved QALYs (£2524 and £2233 less hospital costs and 0.016 and 0.085 more QALYs at 2 and 3 years, respectively) and so dominated VB-first. This economic analysis therefore shows that BET-first is a cost-effective option from an NHS and societal perspective. The sensitivity analysis supported the base-case analysis and BET-first was found to be cost-effective at different willingness-to-pay thresholds. Similar findings were found in all other scenario analyses when considering costs of primary and other hospital healthcare services, taking a broader societal perspective, which includes out-of-pocket expenditure and the costs associated with productivity loss, patient’s adherence to study protocol, the impact of imputation by focusing on participants with complete hospital cost and EQ-5D-5L data only. However, these findings should be interpreted cautiously given the large number of imputed cost values and the substantial probability of a very small QALY difference. 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.
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