Cost-effectiveness analyses: applications in surgery and cardiology Dijksman, Lea

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1 UvA-DARE (Digital Academic Repository) Cost-effectiveness analyses: applications in surgery and cardiology Dijksman, Lea Link to publication Citation for published version (APA): Dijksman, L. M. (2014). Cost-effectiveness analyses: applications in surgery and cardiology General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. UvA-DARE is a service provided by the library of the University of Amsterdam ( Download date: 29 Nov 2017

2 Chapter 9 9 COST-EFFECTIVENESS AND COST UTILITY OF ENDOVASCULAR VERSUS OPEN REPAIR OF RUPTURED ABDOMINAL AORTIC ANEURYSM IN THE AMSTERDAM ACUTE ANEURYSM TRIAL L. M. Dijksman, M. R. Kapma, J. J. Reimerink, A. J. de Groof, C. J. Zeebregts, W. Wisselink, R. Balm, M. G. W. Dijkgraaf and A. C. Vahl Br J Surg Feb;101(3):

3 Cost-effectiveness of trial EVAR versus open repair ABSTRACT Background: Minimally invasive endovascular aneurysm repair (EVAR) could be a surgical technique that improves outcome of patients with ruptured abdominal aortic aneurysm (RAAA). The aim of this study was to analyse the cost-effectiveness and cost utility of EVAR compared with standard open repair (OR) in the treatment of RAAA, with costs per 30-day and 6-month survivor as outcome parameters. Methods: Resource use was determined from the Amsterdam Acute Aneurysm (AJAX) trial, a multicentre randomized trial comparing EVAR with OR in patients with RAAA. The analysis was performed from a provider perspective. All costs were calculated as if all patients were treated in the same hospital (Onze Lieve Vrouwe Gasthuis, teaching hospital). Results: A total of 116 patients were randomized. The 30-day mortality rate was 21 per cent after EVAR and 25 per cent for OR: absolute risk reduction (ARR) 4 4 (95 per cent confidence interval (c.i.) 11 0 to 19 7) per cent. At 6months, the total mortality rate for EVAR was 28 per cent, compared with 31 per cent among those assigned to OR: ARR 2 4 ( 14 2 to 19 0) per cent. The mean cost difference between EVAR and OR was 5306 (95 per cent c.i to ) at 30 days and ( 2477 to ) at 6months. The incremental cost-effectiveness ratio per prevented death was at 30 days and at 6months. There was no significant difference in quality of life between EVAR and OR. Nor was EVAR superior regarding cost utility. Conclusion: EVAR may be more effective for RAAA, but against costs that are non-affordable based on current standards of societal willingness-to-pay for health gains. 142

4 Chapter 9 INTRODUCTION Ruptured abdominal aortic aneurysm (RAAA) is a life-threatening condition, which necessitates immediate treatment, usually by open surgical repair (OR).The overall mortality rate among patients with RAAA is approximately per cent 1. For those who reach hospital alive and are treated by OR, the mortality rate is around 50 per cent and has not changed over the past decade, despite improvements in postoperative care 2. Endovascular aneurysm repair (EVAR) is a treatment modality in which a stent-graft is deployed in the ruptured aorta, using access from the groin. With EVAR, laparotomy is avoided and clamping of the aorta is not necessary. EVAR has proven to be effective in the elective setting 3,4 and could be a treatment that improves outcome of patients with RAAA. Several open studies 5 7 support this hypothesis. Possible drawbacks of EVAR are the high costs of the stent-grafts and limited applicability owing to anatomical suitability of the aortic aneurysm. The Amsterdam Acute Aneurysm (AJAX) trial) 8 was a multicentre randomized trial comparing OR with EVAR in patients with RAAA (registration number: ISRCTN ). In this multicentre trial, which took place in two university hospitals (Academic Medical Centre and VU Medical Centre, Amsterdam) and one teaching hospital (Onze Lieve Vrouwe Gasthuis, OLVG), 116 patients were assigned randomly to either one of the two procedures. Primary endpoints in this trial were mortality and severe morbidity at 30 days, and secondary endpoints were intensive care unit (ICU) stay, mechanical ventilation and use of blood products. The present study was a cost analysis of the AJAX trial performed from a provider perspective, taking into account the events and costs during 6months of follow-up. METHODS The methods and major findings of the AJAX trial have been reported previously8. In brief, all patients with a RAAA in the greater Amsterdam area were identified. The logistics for patients with RAAA was changed with centralization of care in three trial centres. Patients both fit for EVAR and OR were randomized to either treatment. The primary endpoint of the study was combined death and severe complications at 30 days. COST ANALYSIS The present analysis was performed from a provider perspective; direct and indirect medical costs were included using standard methods 9,10. All costs were calculated as if all patients were treated in the same hospital (OLVG, teaching hospital). Resource use was determined from the original prospective AJAX trial database, with direct observations from the moment of admission until discharge from the hospital. 143

5 Cost-effectiveness of trial EVAR versus open repair Table 1. Mean costs per unit. Item Cost per unit Source Surgery Operation room usage Hospital ledger Materials h Stent Medtronic Talent 4, Manufacturer pricelist Extension Medtronic Talent 1, Manufacturer pricelist Stent Endurant 4, Manufacturer pricelist Extension Endurant 80 2, Manufacturer pricelist Extension Endurant 95/120 3, Manufacturer pricelist Tube prosthesis Manufacturer pricelist Bifurcated prosthesis Manufacturer pricelist Balloon Manufacturer pricelist Guidewire Terumo Manufacturer pricelist Guidewire stiff Manufacturer pricelist Angiocatheter Manufacturer pricelist Sheets (per 2) Manufacturer pricelist Occluder Manufacturer pricelist Dacron bypass Manufacturer pricelist Blood products Erythrocytes Dutch costing guideline for health care Thrombocytes Dutch costing guideline for health care Plasma Dutch costing guideline for health care Hospitalization ICU stay a day 2, Dutch costing guideline for health care General ward stay a Dutch costing guideline for health care Diagnostics d Radiology CTA Hospital ledger Ultrasound scan Hospital ledger X-ray abdomen Hospital ledger X-ray thorax Hospital ledger Duplex scan Hospital ledger Others Physiotherapy, per consult Hospital ledger Speech therapy, per consult Hospital ledger Occupational therapy, per Hospital ledger Pathology, mean l Hospital ledger Dialysis Hospital ledger Other diagnostics, mean Hospital ledger Consultation, mean per Hospital ledger Laboratory tests, l 3.40 Hospital ledger Out patient clinic Dutch costing guideline for health care ICU, intensive care unit; CTA, computed tomography. Talent TM, Endurant TM, Medtronic (Minneapolis, Minnesota, USA) 144

6 Chapter 9 Direct observation was incorporated in study procedures, such as for recording duration of surgery, blood products used, duration of admission to the ICU and ward, etc. 8. The volumes of radiology, physiotherapy, pathology, laboratory tests and follow-up of patients not treated in the OLVG were not available, so the mean costs of those treated in the OLVG were used. The actual operation costs for EVAR and OR were calculated using the 2010 price level, based on the costs of personnel, equipment, materials and overhead costs, but not including specialists fees 10. Costs of surgical equipment were determined based on purchase prices and estimated duration of use attributable to the RAAA surgery. Costs of materials included mainly the costs of stent-grafts and related materials. All reoperations took place during the initial hospital stay. Costs of packed cells and fresh frozen plasma were calculated separately; unit costs of these materials were actual purchase prices paid by the hospital. Costs of emergency computed tomography angiography were calculated on the basis of the OLVG tariff. Dutch unit prices of hospitalization per day for general hospitals were used for ward and ICU costs 10. Table 1 shows mean costs per unit. The incremental cost-effectiveness ratio of EVAR versus OR was calculated by dividing the difference in costs by the difference in survival between groups. The incremental 30-day mortality (the difference between study groups in the proportion of patients surviving) was the effect measure. QUALITY OF LIFE Quality of life was investigated using the Medical Outcomes Short Form 36 (SF-36 ; QualityMetric, Lincoln, Rhode Island, USA) and the EQ-5D (EuroQol Group, Rotterdam, The Netherlands) 11,12. These two questionnaires were filled in by surviving patients at 30 days, 3 months and 6 months after surgery. Owing to the acute nature of RAAA at presentation, baseline values could not be obtained for either questionnaire. Therefore, SF-36 normative data for the Dutch population in age specific groups were used to establish baseline values. The time tradeoff tariff of York ( 0 59)13 was used for EQ- 5D values at baseline. Missing values in EQ- 5D were imputed backwards from the last observation. If only first observation(s) were available (30 days and/or 3months), missing values were imputed by last available observation carried forward. Patients who died were assigned a value of 0 at the time of death and all further EQ-5D measures. STATISTICAL ANALYSIS AND ECONOMIC EVALUATION Intention-to-treat analyses were performed. Volume and cost data for 30 days and 6months after randomization were averaged per patient. Because of skewed distributions, assessment of group contrasts was done by calculating 95 per cent confidence intervals (c.i.) for the mean differences following bias-corrected and accelerated nonparametric bootstrapping, drawing samples 145

7 Cost-effectiveness of trial EVAR versus open repair of the same size as the original sample separately for each group and with replacement 14. For each replicated data set, average costs and effects per treatment and the corresponding costeffectiveness ratio were calculated. Calculation of quality-adjusted life-years (QALYs) was done by multiplying the EQ-5D value by time intervals in years preceding this value. A cost utility plane was used to show the average costs and QALYs. The quadrants of the cost utility plane represent possible relationships between average cost difference and average difference in effects in QALYs (for example the right lower quadrant represents cost savings and health gains in favour of the experimental situation). To investigate the possibility that EVAR is cost-effective, the cost-effectiveness acceptability curve was plotted for various levels of willingness-to-pay per life saved up to Differences in mean SF-36 scores were assessed using Student s t test and EQ-5D data were evaluated as percentages. The absolute risk reduction (ARR) was calculated by subtracting the percentage mortality after OR from that after EVAR. Using the ARR, the number needed to treat (NNT) to save one life with EVAR compared with OR was calculated, as 1/ARR. SENSITIVITY AND SUBGROUP ANALYSES Sensitivity analyses were performed for different levels of unit costs and healthcare recourses that contributed most to the total cost difference between patients randomized to OR or EVAR. In the AJAX trial, the intraoperative conversion rate was relatively high (14 per cent, 8 of 57). Therefore, analyses of the effect of conversion on the mean total costs of EVAR were carried out. Finally, subgroup analysis was performed for elderly patients (aged at least 80 years). RESULTS Between April 2004 and February 2011, 520 patients were identified with RAAA, of whom 116 could be randomized. The primary endpoint, combined rate of death and severe complications, was 42 per cent for EVAR and 47 per cent for OR: ARR 5.4 (95 per cent c.i to 23.4) per cent. The 30-day mortality rate was 21 per cent after EVAR and 25 per cent after OR: ARR 4 4 ( 11.0 to 19.7) per cent (NNT 22.7, 95 per cent c.i. 9.1 to 5.0). At 6 months, the mortality rate after EVAR was 28 per cent, compared with 31 per cent for OR: ARR 2.4 ( 14.2 to 19.0) per cent (NNT 41.7, 7.1 to 5.3). At 30 days, the mean total costs for the EVAR group were compared with for OR (mean difference 5306, 95 per cent c.i to ). At 6 months, the mean total costs for the EVAR and OR groups were and respectively (mean difference , 2477 to ) (Table 2). 146

8 Chapter 9 Table 2. Volumes and costs per patient of health care resources EVAR (n=57) # OR (n=59) # Volume Cost (EUR) Volume Cost (EUR) Cost difference (EUR) Costs during 30 days Surgery Total cost per patient 16,589 7,599 Primary surgery , ,938 8,862 (7,083 to +10,506) Reoperation Hospitalization Total costs per patient 14,225 18,316 ICU , ,504-4,240 (-10,262 to +1,792) Ward , , (-1,100 to +1,395) Radiology Total cost per patient (-4 to +123) CTA Ultrasound X-ray thorax X-ray abdomen Duplex scan Laboratory tests (-61 to +616) Other Total costs per patient (-67 to +185) Pathology Consultation Dialysis Physiotherapy Other diagnostics Outpatient clinic (-16 to +8) Total 32,742 27,436 5,306 (-1,854 to +12,659) Additional costs until 6 months Hospitalization 6,969 3,450 ICU , ,961 2,596 (-2,730 to +9,632) Ward , , (-1,227 to +3,745) Radiology Total cost per patient (116 to +233) CTA Ultrasound X-ray thorax X-ray abdomen Duplex scan Laboratory tests (140 to +217) Others Total cost per patient (532 to +1,801) Dialysis Physiotherapy Outpatient clinic (-7 to +40) Total 8,609 3,726 4,883 (-1,749 to + 13,112) Total costs per patient until 6 months 41,351 31,162 10,190 (-2,477 to +24,506) Values in perentheses are 95 per cent confidence intervals. All volumes and costs are per patient. * Radiology data were available for 18 patients in the open repair (OR) group and 20 in the endovascular aneurysm repair (EVAR) group. Reoperation occurred 24 times in 12 patients in the OR group, and 16 times in 12 patients in the EVAR group. Costs of reoperations varied widely from 891 to 11,600. Physiotherapie included occupational therapy and speech therapy. ICU, intensive care unit; CT, computed tomography. 147

9 Cost-effectiveness of trial EVAR versus open repair Details of the various medical costs at 30 days and 6months are presented in Fig. 1. Theatre costs led to the largest differences, which were mostly attributed to the cost of the endovascular stents (mean 7895; 50 per cent of total operation costs) over that of the aortic prostheses used during OR (mean 727; 10 per cent of total operation costs). The incremental costs per prevented death (difference between groups in costs divided by difference in survival) was 120,591 ( 5,306/0.044) at 30 days and ( 10,189/0.024) at 6months. Fig. 1 Box plots showing operation and intensive care unit (ICU) costs at a 30 days and b 6 months in the endovascular repair (EVAR) and open repair (OR) groups. Median (horizontal line within box), interquartile range (box), and range (error bars) excluding outliers (circles) and extreme outliers (asterisks) are shown. QUALITY OF LIFE Quality-of-life questionnaires were completed by 77 per cent of survivors, with no difference between EVAR and OR. In the SF-36 questionnaire, after 6 months, the physical component summary for EVAR was (29 patients) and that for OR was (27 patients) (mean difference 3.56, 95 per cent c.i. 2 to 9). The mental component summary after 6 months was for EVAR and for OR (mean difference 5.25, 11 to 0). After 6 months, the EQ- 5D questionnaire showed no significant difference in scale division between EVAR (32 patients) and OR (31) (Fig. 2). 148

10 Chapter 9 Fig.2 Frequency distribution of EQ-5D TM scores after 6 months. Level 1, no problems; level 2, some problems; level 3, severe problems. EVAR, endovascular aneurysm repair; OR, open repair Fig. 3 Cost-utility plane at 6 months. The majority of the bootstrapped results lie in the right upper quadrant, indicating that endovascular repair (EVAR) is associated with higher costs and fewer complications. QALY, quality-adjusted life year. 149

11 Cost-effectiveness of trial EVAR versus open repair QUALITY-ADJUSTED LIFE-YEARS At 6months, patients in the EVAR group had a mean QALY value of (95 per cent c.i to 0.445) versus (0.164 to 0.433) for the OR group. Fig. 3 shows the difference in costs between OR and EVAR in relation to the difference in QALYs at 6months; with a central point estimate of ( /0.026) per QALY, most bootstrapped results (56.1 per cent) lie in the right upper quadrant of the cost utility plane, indicating that EVAR is associated with higher costs and lower mortality. The upper left (37.6 per cent) and lower right (4.8 per cent) quadrants have fewer bootstrapped results. With a willingness-to-pay per life saved level of , the probability of EVAR being cost-effective is less than 25 per cent (Fig. 4). SENSITIVITY AND SUBGROUP ANALYSIS The impact of varying the unit cost of the endovascular stent was studied. With 25 per cent lower stent costs, the total medical costs of EVAR would have been at 30 days, leading to a mean difference of 3332 (95 per cent c.i to ) compared with OR. At 6months the total medical costs of EVAR would have been , with a mean difference of 8215( 4474 to ) compared with OR. With 50 per cent lower stent costs, difference in total medical costs between EVAR and OR would have been 1470 ( 5764 to 8872) at 30 days and 6354 ( 6416 to ) at 6months. Reducing stent costs further by 75 per cent would result in a mean difference of 448 ( 7755 to 6964) at 30 days and 4436 ( 8405 to ) at 6months. The second sensitivity analysis involved increasing hospitalization and consultation costs. Increasing the costs of ICU stay, ward stay and follow-up consultation, using higher hospital prices, increased the total medical costs at 30 days for EVAR to , compared with for OR (mean difference 5351, 1807 to ). At 6months, the total medical costs would have been and for EVAR and OR respectively (mean difference , 2788 to ). Increasing unit costs increased the total difference in costs between EVAR and OR. Subgroup analysis was performed for eight patients whose procedure was converted from EVAR to OR. The mortality rate in this group was 25 per cent (2 deaths) at 30 days and 38 per cent (3 deaths) at 6 months. At 30 days, the mean total costs for these patients were , compared with for 49 patients who did not have a conversion (mean difference , 5964 to ). At 6months, the mean total costs of a converted procedure were , compared with for unconverted EVAR (mean difference , to ). Subgroup analysis of patients aged 80 years or older versus those younger than 80 years revealed no significant cost differences. 150

12 Chapter 9 Fig. 4 Cost-effectiveness acceptability curve at 6 months. EVAR, endovascular aneurysm repair DISCUSSION Treatment of RAAA using EVAR was not cost-effective compared with OR in this study. EVAR was associated with a slightly lower mortality rate, but higher costs. At 30 days the mean difference in costs for EVAR versus OR was 5306, increasing to at 6months. Nor was there any benefit of EVAR in terms of quality of life. Thirty-day mortality rates in the AJAX trial were low for both EVAR and OR: 21 and 25 per cent respectively. Mortality rates were also similar at 6 months: 28 per cent for EVAR and 31 per cent for OR. The main factor accounting for the cost difference at 30 days was the cost of the stent graft. At 30 days the ARR (4.4 per cent) associated with use of EVAR instead of OR led to a NNT of 22.7 patients. The total cost required to save one person s life (22.7 multiplied by the cost difference of 5306) was At 6months the ARR (2.4 per cent) led to a NNT of 41.7 patients, per life saved. The mean costs of the EVAR group were substantially raised by eight patients who required conversion to open surgery. At 6 months, the mean difference between the converted and nonconverted groups was Conversion in this study was required because of access failure (3) or persisting type I endoleak (5) 8. The results of EVAR could be improved by reducing the conversion rate, perhaps by selecting patients with more favourable anatomy. 151

13 Cost-effectiveness of trial EVAR versus open repair Hayes and colleagues 15 published a worldwide experience of 7040 patients presenting with acute AAA (ruptured or symptomatic) treated with either emergency EVAR or OR. In their review the mean QALYs per patient was 3.09 for EVAR and 2.45 for OR (0.64 difference). EVAR was cost-effective compared with OR at a threshold value of per QALY gained. In 2007, Kapma and co-workers 16 reported the experience of the Groningen cohort; patients were treated preferentially by EVAR and compared with a historical OR group. The authors concluded that treatment with EVAR was not more expensive, although in retrospect this study was too small (49 patients). In 2006, Visser et al. 17 reported a retrospective cost analysis in a nonrandomized cohort of 32 EVARs and 35 ORs. Patients with favourable anatomy were selected for EVAR; all other patients received OR. The mean total 30-day costs were lower for patients who underwent EVAR ( versus for OR), possibly as a result of patient selection. Aune and colleagues18 reported the life-years gained after RAAA in 53 patients aged over 80 years. The operative mortality rate after OR was 47 per cent, but long-term survival in survivors was similar to that of an age- and sex-matched population. Tang and co-workers19 calculated costs for 47 OR procedures for RAAA. The median cost for uncomplicated rupture was 6427 ( 7593; exchange rate 19 October 2013); for 12 complicated ruptures it was ( ) and for 63 elective AAA repairs 4762 ( 5626). Patel et al.20 used a hypothetical cohort patients with RAAA. Repair was cost-effective, with an incremental cost-effectiveness ratio of US $ ( 7862), and remained cost-effective until the perioperative mortality rate reached 88 per cent. Potential limitations of the present cost-effectiveness study are the low inclusion rate, long duration of recruitment and high conversion rate. The true value of EVAR is not only as an alternative for patients who are fit for OR, but more for patients who are not fit for an open procedure. The cost-effectiveness study used cost data from a single Dutch teaching hospital, and it might be argued that the cost determination applies only to this centre. Costs may be different in other countries, but the relative cost difference between the groups randomized to EVAR and OR will probably persist. The results of open surgery here were excellent. Scenario analysis revealed that if the mortality rate was 48 per cent, as expected, then the difference in costs between EVAR and OR would have increased by 5 per cent, as patients who die after surgery need fewer bed-days. Another limitation was that the AJAX database could not supply the volumes of radiology, physiotherapy, pathology, laboratory tests and follow-up of patients not treated in the OLVG. Therefore, mean costs of patients treated at OLVG were used. However, these costs are small in comparison to all other costs (2 5 per cent). 152

14 Chapter 9 ACKNOWLEDGEMENTS M.R.K. and L.M.D. contributed equally to this article. Disclosure: The authors declare no conflict of interest. MGWD is a fan of Feyenoord. REFERENCES 1. Kantonen I, Lepantalo M, Brommels M, Luther M, Salenius JP, Ylonen K. Mortality in ruptured abdominal aortic aneurysms. The Finnvasc Study Group. Eur J Vasc Endovasc Surg 1999; 17: Hoornweg LL, Storm-Versloot MN, Ubbink DT, Koelemay MJ, Legemate DA, Balm R. Meta analysis on mortality of ruptured abdominal aortic aneurysms. Eur J Vasc Endovasc Surg 2008;35: Greenhalgh RM, Brown LC, Kwong GP, Powell JT, Thompson SG. Comparison of endovascular aneurysm repair with open repair in patients with abdominal aortic aneurysm (EVAR trial 1), 30-day operative mortality results: randomised controlled trial. Lancet 2004; 364: Prinssen M, Verhoeven EL, Buth J, Cuypers PW, van Sambeek MR, Balm R et al.; Dutch Randomized Endovascular Aneurysm Management (DREAM) Trial Group. A randomized trial comparing conventional and endovascular repair of abdominal aortic aneurysms. N Engl J Med 2004; 351: Holt PJ, Karthikesalingam A, Poloniecki JD, Hinchliffe RJ, Loftus IM, Thompson MM. Propensity scored analysis of outcomes after ruptured abdominal aortic aneu-rysm. Br J Surg 2010; 97: Rayt HS, Sutton AJ, London NJ, Sayers RD, Bown MJ. A systematic review and meta-analysis of endovascular repair (EVAR) for ruptured abdominal aortic aneurysm. Eur J Vasc Endovasc Surg 2008; 36: Sadat U, Boyle JR,Walsh SR, Tang T, Varty K, Hayes PD. Endovas-cular vs open repair of acute abdom-inal aortic aneurysms a systematic review and meta-analysis. J Vasc Surg 2008; 48: Reimerink JJ, Hoornweg LL, Vahl AC, WisselinkW, van den Broek TA, Legemate DA et al. Endovascular repair versus open repair of ruptured abdominal aortic aneurysms: a multicenter randomi-zed controlled trial. Ann Surg 2013; 258:

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