Rivaroxaban for the prevention of stroke and systemic embolism in people with atrial fibrillation

Evidence-based recommendations on rivaroxaban (Xarelto) for preventing stroke and systemic embolism in adults with non-valvular atrial fibrillation.

# Recommendations
Rivaroxaban is recommended as an option for the prevention of stroke and systemic embolism within its licensed indication, that is, in people with non-valvular atrial fibrillation with one or more risk factors such as:
congestive heart failure
hypertension
age 75 years or older
diabetes mellitus
prior stroke or transient ischaemic attack.
Decide whether to start treatment with rivaroxaban after an informed discussion with the person about its risks and benefits compared with warfarin, apixaban, dabigatran etexilate and edoxaban. For people taking warfarin, consider the potential risks and benefits of switching to rivaroxaban taking into account their level of international normalised ratio (INR) control.# The technology 
Rivaroxaban (Xarelto, Bayer HealthCare) is an anticoagulant that directly inhibits activated factor X (factor Xa). Factor Xa is a key component in the formation of blood clots. Rivaroxaban has a UK marketing authorisation for the 'prevention of stroke and systemic embolism in adult patients with non-valvular atrial fibrillation with one or more risk factors such as: congestive heart failure, hypertension, age 75 years or older, diabetes mellitus, prior stroke or transient ischaemic attack'.
According to the summary of product characteristics, approximately 14% of people treated with rivaroxaban in clinical studies experienced adverse reactions. Bleeding occurred in approximately 3.3% of patients and anaemia in approximately 1% of patients. Other common adverse reactions were nausea and an increase in transaminases. The summary of product characteristics states that the risk of bleeding may be increased in certain patient groups, for example those with uncontrolled severe arterial hypertension and/or those taking other treatments that affect haemostasis. For full details of adverse reactions and contraindications see the summary of product characteristics.
The price of rivaroxaban is 58.80 for a pack of 28 15-mg tablets and 58.80 for a pack of 28 20mg tablets (MIMS March 2012). Costs may vary in different settings because of negotiated procurement discounts.# The manufacturer's submission 
The Appraisal Committee considered evidence submitted by the manufacturer of rivaroxaban and a review of this submission by the Evidence Review Group (ERG).
The main clinical effectiveness evidence came from one multicentre, double-blind randomised controlled trial. The ROCKET-AF trial ('Rivaroxaban once daily oral direct factor Xa inhibitor compared with vitamin K antagonism for prevention of stroke and embolism trial in atrial fibrillation') compared rivaroxaban with dose-adjusted warfarin. The manufacturer also compared rivaroxaban with aspirin and dabigatran etexilate (110 mg or 150 mg twice a day) using a network meta-analysis in people for whom anticoagulation therapy was considered suitable. The ROCKET-AF trial was designed as double-blind, double dummy trial comparing rivaroxaban (20 mg or 15 mg once a day) with warfarin (target INR of 2.0 to 3.0) for the prevention of stroke and thromboembolic events in people with non-valvular atrial fibrillation at risk of future thromboembolic events. People were randomly allocated to one of the two treatment groups with equal probability (1:1 allocation ratio). The study took place in 45 countries, including the UK, and a total of 14,264 people were enrolled across the two treatment arms (rivaroxaban n = 7131, warfarin n = 7133). Treatment continued until approximately 405 adjudicated primary efficacy end point events had occurred in the per-protocol population on treatment. As a result, the time on treatment varied from patient to patient depending on when they enrolled in the trial. The median duration of treatment was 590 days.
The primary efficacy end point in ROCKET-AF was a composite of stroke (ischaemic and haemorrhagic stroke) and non-central nervous system systemic embolism. The primary safety end point was defined as a composite of major bleeding and clinically relevant non-major bleeding. To show non-inferiority in preventing stroke and non-central nervous system embolism, the upper boundary of the confidence interval of the hazard ratio (HR) for rivaroxaban compared with warfarin had to be less than 1.46. Once non-inferiority was demonstrated for the primary outcome, further analyses investigated superiority of rivaroxaban over warfarin.
More than 50% of people in the trial received treatment for at least 18 months. The median age of study participants was 73 years and 60.3% were men. The majority of the trial population (62.4%) had previously received warfarin therapy and 36.5% had previously received aspirin. Risk of stroke at baseline was classified according to CHADS2 score, which is used to predict the risk of stroke in people with atrial fibrillation. The trial entry criteria included a history of stroke, transient ischaemic attack or systemic embolism, or a CHADS2 score of 2 or more. The mean CHADS2 score was 3.48 for the rivaroxaban group and 3.46 for the warfarin group; 99.98% of the trial population had a baseline CHADS2 score of 2 or more and 86.95% a baseline CHADS2 score of 3 or more. Three participants (0.02% of the trial population) had a baseline CHADS2 score of 1. In the warfarin group the mean time in therapeutic range for the INR range of 2.0 to 3.0 was 55% (58% median). Some variability was observed in time in therapeutic range by region: north America had the highest overall INR control, followed by western Europe, Latin America, Asia Pacific, and eastern Europe.
Three analyses were defined in the manufacturer's submission for the efficacy analysis: the intention-to-treat set (all patients randomised), the safety-on-treatment set (all intention-to-treat patients who had taken at least one dose of the study drug and were followed for events) and the per-protocol set (all intention-to-treat patients excluding those who had major pre-defined protocol deviations). The primary non-inferiority analysis of the ROCKET-AF trial was conducted on the per-protocol and the safety-on-treatment population data sets. The superiority analyses were conducted on the safety-on-treatment population data sets. In addition to these analyses, sensitivity analyses were performed to assess non-inferiority and superiority in the intention-to-treat population. The primary safety analysis was conducted on the safety-on-treatment population data.
Pre-planned subgroup analyses were conducted. These were by region, prior use of vitamin K antagonists (such as warfarin), and history of stroke, transient ischaemic attack, and non-central nervous system systemic embolism. Other subgroups included prior chronic aspirin use, sex, age, family origin, renal function, body mass index, weight, CHADS2 score, congestive heart failure, hypertension, diabetes, type of atrial fibrillation, proton pump inhibitor use at baseline, and prior myocardial infarction. Results were summarised by subgroup based on data from the safety-on-treatment and intention-to-treat populations.
The non-inferiority of rivaroxaban compared with warfarin was demonstrated for the primary outcome (composite of stroke and non-central nervous system systemic embolism) in both the per-protocol and safety-on-treatment populations. The results for the per-protocol population were HR 0.79 (95% confidence interval  0.66 to 0.96) and HR 0.79 (95% CI 0.65 to 0.95) for the safety-on treatment population. Superiority of rivaroxaban over warfarin was also demonstrated in the safety-on-treatment population, but was not demonstrated for this outcome in the sensitivity analysis using the intention-to-treat population data set (HR 0.88, 95% CI 0.75 to 1.03).
For the primary safety end point of major or non-major clinically relevant bleeding, the results from the safety-on-treatment population data for ROCKET-AF suggest a comparable safety profile for rivaroxaban and warfarin, with no statistically significant difference between the two treatments (HR 1.03, 95% CI 0.96 to 1.11). Bleeding sites for the primary safety end point differed between treatment groups. Rivaroxaban was more often associated with bleeding at sites throughout the gastrointestinal tract (3.15% compared with 2.16%, p < 0.001) but intracranial haemorrhage rates were significantly lower with rivaroxaban than with warfarin (0.5% compared with 0.7%, p = 0.02). Following a request from the ERG the manufacturer provided subgroup analyses for the safety-on-treatment and intention-to-treat populations in people who had previously used vitamin K antagonists, people who had not previously used vitamin K antagonists, people with a time in therapeutic range below 60%, and those with a time in therapeutic range above 60%. In the safety-on-treatment population, superiority of rivaroxaban compared with warfarin was demonstrated for the primary outcome (composite of stroke and non-central nervous system systemic embolism) in people who had not previously used vitamin K antagonists (HR 0.72, 95% CI 0.53 to 0.97) but not in people who had previously used vitamin K antagonists (HR 0.84, 95% CI 0.66 to 1.08).
The manufacturer undertook a Bayesian network meta-analysis comparison of rivaroxaban with warfarin, aspirin, no treatment and dabigatran etexilate. The clinical evidence for the rivaroxaban with warfarin comparison was taken from the ROCKET-AF trial. Evidence for the other comparators was obtained from studies found by a systematic literature search. The manufacturer identified 18 studies for inclusion in the network meta-analysis:
-ne comparing rivaroxaban with warfarin
seven comparing aspirin with placebo or control
eight comparing warfarin with aspirin
-ne comparing a vitamin K antagonist with clopidogrel plus aspirin
-ne comparing dabigatran etexilate with warfarin (the RE-LY study). The manufacturer reported network meta-analysis results for the outcomes using the ROCKET-AF safety-on-treatment population data set. At the request of the ERG, the manufacturer also provided the results for the outcomes using the ROCKET-AF intention-to-treat population dataset. The efficacy estimates from this network meta-analysis using the ROCKET-AF safety-on-treatment population data set were used in the manufacturer's cost-effectiveness analyses.
The ERG undertook an exploratory network meta-analysis comparing rivaroxaban with dabigatran etexilate, aspirin, placebo, and adjusted standard dose warfarin. It included data from eight of the 18 studies from the manufacturer's network meta-analysis:
-ne comparing dabigatran etexilate with warfarin
-ne comparing rivaroxaban with warfarin
three comparing aspirin with warfarin
three comparing warfarin with placebo. The ERG judged that including only these eight trials would reduce the amount of heterogeneity in the network. Only dosing strategies that the ERG considered to be comparable were included (that is, rivaroxaban 20 mg per day, dabigatran etexilate 150 mg twice a day, aspirin 300 mg per day, and adjusted dose warfarin aiming at a target INR range between 2 and 3). Dabigatran etexilate at a dose of 110 mg twice daily was not included in the analysis because the economic model could not accommodate a dosing regimen in which the dose is reduced from 150 mg twice daily to 110 mg twice daily when the patient reaches the age of 80 years. A fixed-effect model was used because of the high degree of homogeneity between the included trials. The efficacy estimates from this network meta-analysis were used in the ERG's cost-effectiveness analyses.
The manufacturer developed a Markov model that compares rivaroxaban (20 mg once a day) with warfarin (adjusted dose warfarin at 4.5 mg once a day, target INR 2.5, range 2.0 to 3.0), aspirin (150 mg once a day), dabigatran etexilate (110 mg to 150 mg twice a day) and no treatment. The population in the model is the same as the ROCKET-AF safety-on-treatment population. The model has a lifetime time horizon and a UK NHS perspective.
The model included the following health states:
anticoagulant initiation
stable atrial fibrillation (on or off therapy)
minor stroke (on or off therapy)
major stroke (on or off therapy)
post minor stroke (on therapy)
post major stroke (on therapy)
minor bleed (on or off therapy)
major bleed (on or off therapy)
intracranial bleed (on or off therapy)
post intracranial bleed (on or off therapy)
systemic embolism (on or off therapy)
myocardial infarction (on or off therapy)
post myocardial infarction (on or off therapy)
death.The ROCKET-AF trial results for the safety-on-treatment population were used to inform the efficacy estimates for rivaroxaban compared with warfarin, rivaroxaban compared with warfarin in people whose atrial fibrillation is poorly controlled on warfarin, and the vitamin K antagonist-naive model populations. The characteristics of the population for the analyses of rivaroxaban compared with aspirin, dabigatran etexilate and no treatment were based on the patient characteristics of a UK GP practice-based survey (Gallagher et al. 2008). Efficacy estimates for rivaroxaban compared with dabigatran etexilate and aspirin were obtained from the manufacturer's network meta-analysis.
The manufacturer classified all model events as either transient or permanent depending on associated long-term costs and consequences:
Systemic embolism, minor extracranial bleeds and major extracranial bleeds were assumed to have no lasting clinical or economic consequences and as such were considered transient events in the model.
Minor stroke, major stroke, intracranial bleeding and myocardial infarction were considered by the manufacturer to be permanent events, in the sense that they have lasting clinical and economic consequences. Consequently, the manufacturer developed post-event health states to account for the different risks, costs and utilities associated with surviving a permanent event.
The manufacturer highlighted that increasing age was an important risk factor for ischaemic stroke and systemic embolism, and adjusted the baseline risk of these events to account for patients aging as they move through the model. Risks were calculated using the Framingham risk equations. In the model, a weighted average relative risk (weighted by the proportion of patients in each risk group at initiation) is calculated for each age group and applied to the baseline risk as patients enter that age group. The risks of extracranial bleeding, intracranial bleeding and myocardial infarction were assumed to be independent of time and, therefore, were not adjusted for.
The baseline risk of each event was adjusted according to the treatment regimen the patient was receiving. Patients may stop their primary therapy and switch to a pre-specified secondary therapy at any time, although the risk adjustment applied for the remainder of that cycle is that of the primary therapy. The probabilities of treatment discontinuation for warfarin and rivaroxaban were based on data from the ROCKET-AF trial. The manufacturer assumed that treatment-discontinuation rates for aspirin, dabigatran etexilate and placebo were equivalent to that for rivaroxaban, given the similarity of administration between these interventions.
The health-state utility values and treatment-related utility values in atrial fibrillation were obtained from published sources identified by a systematic literature search. The ROCKET-AF trial did not include a generic measure of health-related quality of life (such as the EQ-5D) that could be used to estimate utilities in the model. The estimates of resources and costs were obtained from NHS reference costs for 2009/10 and systematic literature searching. The manufacturer's model categorised monitoring costs into the following distinct phases: initiation, maintenance, and re-initiation. The manufacturer's model calculated the quarterly cost of initiation, maintenance and re-initiation by taking a weighted average of each cost; the costs of the individual phases were weighted by the proportion of people treated in primary and secondary care, as indicated by the manufacturer's survey. The resulting annual cost estimates for warfarin monitoring were 663 (448 in primary care and 215 in secondary care) for the first year and 525 (359 in primary care and 166 in secondary care) for subsequent years.
The manufacturer's base-case analysis of rivaroxaban compared with warfarin used only statistically significant data from the ROCKET-AF safety-on-treatment population. The analysis produced an incremental cost of 740 and a QALY gain of 0.039 resulting in an incremental cost-effectiveness ratio (ICER) of 18,883 per quality-adjusted life year (QALY) gained. The manufacturer also presented the results of four subgroup analyses:
For rivaroxaban compared with warfarin in people whose INR is poorly controlled on warfarin, rivaroxaban dominated (was more effective and cost less) warfarin.
For rivaroxaban compared with warfarin in people who had not previously received warfarin, the ICER was 15,494 per QALY gained.
For rivaroxaban compared with aspirin, the ICER was 2083 per QALY gained.
For rivaroxaban compared with dabigatran etexilate, rivaroxaban dominated dabigatran etexilate. The manufacturer carried out univariate sensitivity analysis on the base case, scenario analyses and subgroup analyses. The main drivers of the model results were consistent across analyses, with the cost of warfarin monitoring in primary care having a major impact on all ROCKET-AF-based analyses. The probabilistic sensitivity analyses indicated that, using the base case, rivaroxaban had a 75% probability of being cost effective at a maximum acceptable ICER of 20,000 per QALY gained and an 88% probability at 30,000 per QALY gained. The manufacturer's scenario analysis of rivaroxaban compared with warfarin used all point estimates from the ROCKET-AF safety-on-treatment population regardless of their statistical significance (that is, both statistically significant and non-statistically significant point estimates were used). The resulting ICER was 8732 per QALY gained.
In the ERG's view, a Markov model was an appropriate choice for modelling the chronic condition of atrial fibrillation. The ERG noted that the manufacturer chose a cycle length of 3 months and that only one event per 3-month cycle was possible because of the nature of the model. The manufacturer acknowledged that, in reality, people may experience more than one event in 3 months, but clinical opinion was that the probability of this would be low. The ERG agreed that assuming one event per model cycle was necessary and reasonable. However, the ERG noted that the manufacturer's model also suspends the risk of further events in the subsequent model cycle. The ERG considered that this additional suspension of risk was likely to bias the analysis against the more effective treatment because the overall event rate would be lower, and the potential to demonstrate clinical and economic benefits would also be lower.
The ERG identified the following limitations to the model's structural assumptions and parameter sources:
not separating out the number of hospital visits needed by people who were within and outside recommended INR control
not adjusting risk of bleeding by age; not adjusting utility by age
the source of myocardial infarction risk for people treated with aspirin
-ut of date source of post-myocardial infarction mortality risk
double counting of re-initiation costs of warfarin monitoring
suspending the risk of further events for the subsequent model cycle after an event
excluding transient ischaemic attack as a potential event.
The ERG presented an exploratory analysis in which, if possible, adjustments were made to account for the limitations identified (see section 3.18). The analysis for rivaroxaban compared with warfarin produced an incremental cost of 1134 and a QALY gain of 0.034, resulting in an ICER of 33,758 per QALY gained. Similarly, for warfarin-naive people, after incorporating the ERG's model adjustments, the ICER for rivaroxaban compared with warfarin increased from 15,494 to 29,894 per QALY gained. However, rivaroxaban remained dominant in people whose INR was poorly controlled on warfarin after the ERG's model adjustments were incorporated. The structure of the manufacturer's model meant it wasn't possible to remove risk suspension or add transient ischaemic attack as a potential event. Consequently, the ERG was unable to fully quantify the impact of these limitations on the ICERs. However, the ERG considered that suspending risk and excluding transient ischaemic attack as an event would favour rivaroxaban (that is, the removal of these limitations would decrease the ICER for rivaroxaban compared with warfarin), because warfarin is generally less effective than rivaroxaban (based on the safety-on-treatment population of ROCKET-AF).
In the ERG's view the manufacturer's base-case model is driven by the cost of anticoagulation monitoring rather than the differential effectiveness of rivaroxaban and warfarin. The ROCKET-AF trial showed that, for most outcomes, there was no statistically significant difference between rivaroxaban and warfarin. The ERG highlighted that when the cost of anticoagulation monitoring was separated out by INR range the ICER substantially increased from 18,883 per QALY gained to 27,281 per QALY gained. In addition, the ERG's scenario analysis using the alternative anticoagulation monitoring costs of 242 per person (discussed by the Committee in the ongoing appraisal of dabigatran etexilate for the prevention of stroke and systemic embolism in atrial fibrillation) increased the ICER to 62,568 per QALY gained.
The ERG was concerned that the trials included in the network meta-analysis presented by the manufacturer to compare rivaroxaban with aspirin and dabigatran etexilate were heterogeneous. The high levels of heterogeneity were not shown when the ERG conducted its own network meta-analysis restricting the network to the comparators specified in the final scope. When the ERG applied the treatment effects estimated by its network meta-analysis to the manufacturer's model, and a full incremental analysis of rivaroxaban, dabigatran etexilate, warfarin and aspirin was conducted, an ICER of 34,680 per QALY gained was obtained for dabigatran etexilate compared with rivaroxaban, whereas rivaroxaban had dominated dabigatran etexilate in the manufacturer's analysis. The ERG applied further adjustments to account for the following limitations:
the absence of a post-systemic embolism health state
not adjusting bleeding risk by age
not adjusting utility by age
-ut of date source of post-myocardial infarction mortality risk
assuming equivalent discontinuation rates. This reduced the ICER to 12,701 per QALY gained for dabigatran etexilate compared with rivaroxaban. Exploratory analysis assuming an equivalent ability of rivaroxaban and dabigatran etexilate to prevent myocardial infarction further decreased the ICER to 3578 per QALY gained for dabigatran etexilate compared with rivaroxaban.
The ERG noted the presence of potential biases in the model, with limitations of risk suspension and the absence of transient ischaemic attack and dyspepsia as adverse reactions. Removing risk suspension is likely to favour dabigatran etexilate whereas including transient ischaemic attack and dyspepsia is likely to reduce the ICER for rivaroxaban compared with dabigatran etexilate. Furthermore, the ERG noted that there is a large amount of uncertainty in the model and that the model is highly sensitive to even small changes to the discontinuation rates. Therefore, the ERG concluded that the results of the probabilistic sensitivity analysis should be taken into account when considering its alternative ICER for dabigatran etexilate compared with rivaroxaban. The probabilistic sensitivity analysis indicated that dabigatran etexilate was dominant in 45% of the 1000 runs and dominated in 35% of runs.

# Manufacturer's additional analyses
The manufacturer provided additional analyses in response to the Appraisal Committee's request for further clarification on the cost effectiveness of rivaroxaban presented in the appraisal consultation document. The manufacturer provided a revised cost-effectiveness analysis incorporating the following amendments requested by the Appraisal Committee:
data from the General Practice Research Database to provide event rates according to baseline level of stroke risk and the distribution of patients with different CHADS2 scores from the study of Gallagher et al. (2008)
all the efficacy point estimates from the safety-on-treatment population of the ROCKET-AF trial
revised event rate in the warfarin arm to reflect the time in therapeutic range achieved in trial centres in western Europe (60.62%)
fixed annual warfarin INR monitoring cost of 242 per person in the sensitivity analysis only.
In addition to the amendments requested by the Appraisal Committee, the manufacturer also amended the model to include the following:
Revised annual warfarin INR monitoring cost of 580. The manufacturer used the same unit costs as the original model; however, the number of visits needed for the re-initiation was reduced from seven to five per 3-month cycle. The costs associated with warfarin monitoring in primary care in the updated model were 175.50 for initiation of warfarin (calculated as a weighted average of patients who had, and had not received previous warfarin), 135 for maintenance on warfarin and 135 for re-initiation of warfarin.
Case fatality rates of 90 days instead of the 30-day rates in the original model.
Updated 'real world' discontinuation rates. For warfarin these came from the General Practice Research Database. For rivaroxaban they were calculated by applying relative risks from the General Practice Research Database to discontinuation rates from the ROCKET-AF trial.
Treatment-related disutility applied to warfarin of 0.05. This was obtained from a study evaluating how patients with atrial fibrillation (attending GP- and hospital-led clinics) value different health outcomes. The disutility figures for warfarin were weighted by the UK distribution of primary and secondary care anticoagulation management.
Updated results for rivaroxaban compared with aspirin based on an additional indirect comparison. This comparison used only trials comparing rivaroxaban with warfarin and warfarin with aspirin, to reduce the network heterogeneity.
The manufacturer presented the following cost-effectiveness results when all the amendments in sections 3.23 and 3.24 were applied, with an annual warfarin INR monitoring cost of 580 (that is, excluding the Appraisal Committee's request to incorporate a fixed annual warfarin INR monitoring cost of 242 per person):
for rivaroxaban versus warfarin in the licensed population (the population with one or more risk factors for stroke), an incremental cost of 705, an incremental QALY of 0.2459 resulting in an ICER of 2869 per QALY gained
for rivaroxaban versus warfarin in the population whose INR is poorly controlled on warfarin, rivaroxaban dominated warfarin
for rivaroxaban versus warfarin in the population for whom warfarin is considered unsuitable, the ICER was 9170 per QALY gained.
The manufacturer presented the following cost-effectiveness results when all the amendments detailed in sections 3.23 and 3.24 were applied, with an annual warfarin INR monitoring cost of 242 per person (that is, including all of the Appraisal Committee's requests):
for rivaroxaban versus warfarin in the licensed population (the population with one or more risk factors for stroke), an incremental cost of 2220, a QALY gain of 0.2459 resulting in an ICER of 9031 per QALY gained
for rivaroxaban versus warfarin in the population whose INR is poorly controlled on warfarin, the ICER was 4350 per QALY gained.
The ERG provided a critique and exploratory analysis of the manufacturer's additional analyses. The ERG agreed that the manufacturer had adequately provided a model cohort representative of people with atrial fibrillation in the UK, and that the analysis was based on all efficacy point estimates from the ROCKET-AF trial. The ERG also agreed that it was reasonable to use a discontinuation rate of five and a 90-day case fatality rate in the model. However the ERG noted that the Committee's request to evaluate the effect of low time in therapeutic range was addressed as an amendment to the base case rather than the subgroup analysis requested. The ERG noted that varying the risk of stroke and systemic embolism according to level of INR control resulted in an increase in the ICER of 3742 per QALY gained.
In the ERG's view, the manufacturer's inclusion of a disutility for warfarin in the model was not appropriate. The ERG noted that the manufacturer had not provided any justification for the assumption that no disutility is associated with rivaroxaban, aspirin or dabigatran etexilate. The ERG pointed out that there is evidence of disutility associated with other oral anticoagulants such as dabigatran etexilate and therefore it is unreasonable to assume there is no disutility associated with rivaroxaban. The ERG found that removing the disutility for warfarin has a substantial impact on the ICER, increasing it from 2869 to 10,764 per QALY gained.
The ERG re-ran the manufacturer's updated cost-effectiveness analysis. The ERG noted that in both the original and updated models the manufacturer had categorised systemic embolism as a temporary event. The ERG judged that in order to adequately approximate a post-systemic embolism health state (which would account for the increased risk of stroke following a systemic embolism) it was appropriate to amend the model so that after a systemic embolism patients move into the post-minor stroke health state. The ERG also noted that the manufacturer's updated model continues to use the out of date source of post-myocardial infarction mortality risk. The ERG judged that it was more appropriate to use an updated mortality risk post myocardial infarction that took account of current use of statins. The ERG's analysis included a fixed annual warfarin INR monitoring cost of 242 per person as requested by the Appraisal Committee (see section 3.23) but did not include any disutility associated with warfarin or any other treatment (see section 3.24). The ERG's revised analysis for rivaroxaban compared with warfarin produced an incremental cost of 1815, an incremental QALY of 0.061 and an ICER of 29,537 per QALY gained.
See the manufacturer's submission and the ERG report for full details of all the evidence.# Consideration of the evidence
The Appraisal Committee reviewed the data available on the clinical and cost effectiveness of rivaroxaban, having considered evidence on the nature of stroke and systemic embolism and the value placed on the benefits of rivaroxaban by people with atrial fibrillation, those who represent them, and clinical specialists. It also took into account the effective use of NHS resources.
The Committee was aware that the main concerns for people with atrial fibrillation were fear of having a stroke and anxiety about the difficulty of keeping the INR within the therapeutic range. The Committee heard from the clinical specialists, patient experts and from comments received during consultation that the current standard treatment for preventing stroke and systemic embolism in people with atrial fibrillation is warfarin, and that because aspirin is less effective it is used only in people for whom warfarin is unsuitable. The Committee also heard that warfarin, although an effective treatment, it is associated with a number of problems. The Committee was aware from the patient expert and from comments received during consultation that taking warfarin adversely affects quality of life. This is because people taking warfarin often worry about their level of INR control and they might find regular GP and hospital visits disruptive and inconvenient. The Committee heard from the clinical specialists that a substantial proportion of people taking warfarin have poorly controlled INR and are often not within the target therapeutic range at any one time. In particular, older people with atrial fibrillation are more likely to have poorly controlled INR because of comorbidities. The clinical specialists also explained that the need for regular monitoring and dose adjustments, occasionally involving complicated regimens such as different doses on alternate days, can cause difficulties with adherence to treatment. The Committee recognised the potential benefits of alternatives such as rivaroxaban for people with atrial fibrillation, including the positive effect on quality of life of removing the restrictions and difficulties associated with taking warfarin.
The Committee considered the clinical-effectiveness data from the ROCKET-AF trial comparing rivaroxaban with warfarin. It noted that this study was the basis of the clinical-effectiveness evidence in the manufacturer's submission. The Committee noted that the efficacy analysis in the manufacturer's submission had been undertaken on three different populations in the ROCKET-AF trial, the intention-to-treat set (all randomised patients), the safety-on-treatment set (all intention-to-treat patients who had taken at least one dose of study drug and were followed for events) and the per-protocol set (all intention-to-treat patients excluding those who have major pre-defined protocol deviations). The Committee noted that the manufacturer had presented data from the safety-on-treatment population for its primary analyses. The Committee heard from the clinical specialists that using a trial intention-to-treat population was considered to be the gold standard for estimating clinical effectiveness in a superiority trial, but the primary objective of ROCKET-AF was to establish non-inferiority of rivaroxaban compared with warfarin so the primary analysis was different. The Committee noted the comments received during consultation that suggested that it would be more appropriate to consider the intention-to-treat population rather than the safety-on-treatment population. The Committee reconsidered which of the two study populations was the most appropriate. The Committee noted that the intention-to-treat population included people who had either had no treatment or switched treatment during the trial, and agreed that the estimates derived from the safety-on-treatment population of the ROCKET-AF trial provided an adequate basis for evaluating clinical effectiveness.
The Committee noted that a key uncertainty highlighted by the ERG was the generalisability of the results of ROCKET-AF to people diagnosed with atrial fibrillation in the NHS. The Committee noted that the mean time in therapeutic range for the INR range of 2.03.0 for warfarin was 55% for the safety-on-treatment population in the ROCKET-AF trial. The clinical specialists confirmed this could be considered to be around the lower end of the level of control that would be expected in UK clinical practice, but there is considerable variation between different centres and also between different settings, depending on the patient group. The Committee noted that the ROCKET-AF trial had been undertaken in a number of countries, which did not all achieve similar levels of time in therapeutic range. The majority (66.5%) of the participants were recruited from centres in eastern Europe, Latin America and Asia, and in these centres the proportion of time in therapeutic range was lower than in the centres in North America and western Europe. The Committee was concerned that the effectiveness of warfarin could be underestimated if the proportion of time in therapeutic range was low, and that the UK context might be better reflected by results from centres where the time in therapeutic range in the warfarin arm more closely matched the usual levels in the UK. The Committee concluded that the trial results were broadly applicable to a UK setting, but for those already taking warfarin the current level of INR control should be taken into account in any decision to switch to rivaroxaban.
The Committee also noted that patients in the ROCKET-AF trial had a mean CHADS2 score of 3.47, and that an inclusion criterion of the trial was a baseline CHADS2 score of 2 or more. The scope specified that the appraisal population would be people with a medium to high risk of stroke. The clinical specialists confirmed that people with a CHADS2 score of 3 or more would be at high risk of stroke and that this population was typical of people seen in secondary care. However, this did not necessarily represent people with atrial fibrillation treated in primary care, who tended to have a lower risk of stroke. The Committee heard that people with atrial fibrillation treated with warfarin in primary care often have a CHADS2 score of less than 2 and that it is estimated that between 20 and 75% of people with atrial fibrillation and a CHADS2 score of less than 2 are prescribed warfarin in the UK. Only 0.02% of the trial population had a CHADS2 score less than 2. The clinical specialists agreed that it was likely that although people with a CHADS2 score of 2 or more would benefit similarly to those in the ROCKET-AF trial, this cannot be assumed for people with a CHADS2 score of less than 2. The Committee noted the comments received during consultation that suggested that consultees and commentators had differing opinions on the generalisability of the results of ROCKET-AF to UK clinical practice. The Committee was made aware by the manufacturer that a systematic review of the literature had suggested that there does not appear to be an interaction between treatment effect and baseline CHADS2 risk. The Committee heard from the manufacturer that rivaroxaban would be indicated for atrial fibrillation in people with one or more risk factors for stroke, which equates to a CHADS2 score of 1 or more. The Committee noted that the European Medicines Agency had stated in the 'European public assessment report' for rivaroxaban that efficacy results were essentially consistent in important subgroups, such as different CHADS2 scores (CHADS2 scores 2 to 6).The Committee accepted that, given the broad spectrum of risk covered by the licensed indication for rivaroxaban, there was no plausible reason to expect that the results of ROCKET-AF would not translate to people with a lower CHADS2 score. However the Committee was mindful of the very small number of patients recruited to the ROCKET-AF trial with a baseline CHADS2 score of less than 2, but concluded that the results of the ROCKET-AF trial were generalisable to UK clinical practice.
The Committee discussed the safety data from the ROCKET-AF trial. It noted that analysis of the primary safety end point of all major and non-major clinically significant bleeding events showed no significant differences between rivaroxaban and warfarin. There was a significant reduction in the rate of fatal bleeds and intracranial haemorrhage with rivaroxaban compared with warfarin, but a higher rate of gastrointestinal bleeds. The Committee heard from the patient experts that intracranial bleeds were considered to be a more serious complication than gastrointestinal bleeds in clinical practice, because they were more difficult to treat and often result in permanent disability. The Committee noted that the possible uncertainty in these results related to the relatively low proportion of time in therapeutic range of 55% in the warfarin arm of the trial, but concluded that the primary safety end point showed no statistically significant difference between rivaroxaban and warfarin.
The Committee then discussed the indirect clinical-effectiveness evidence for rivaroxaban compared with dabigatran etexilate and aspirin. The Committee noted that the population in the study comparing dabigatran etexilate with warfarin (RE-LY) had a lower risk of stroke (mean CHADS2 score 2.1) than the population in the ROCKET-AF trial (mean CHADS2 score of 3.47). The Committee noted that the manufacturer's interpretation of its network meta-analysis was that there was no significant difference between rivaroxaban and dabigatran etexilate for any outcome. The Committee noted the ERG's concerns about the validity of the manufacturer's network meta-analysis because of the clinical heterogeneity of the included trials, and the different levels of time in therapeutic range in the warfarin arms of the rivaroxaban and dabigatran etexilate trials. The Committee also noted that both the manufacturer's and ERG's network meta-analyses contained wide confidence intervals, and therefore the resulting efficacy point estimates were subject to considerable uncertainty. The Committee noted the comments received during consultation suggesting that the Committee should reconsider the value of the network meta-analysis. The Committee also noted the additional indirect comparison submitted by the manufacturer during consultation comparing rivaroxaban with aspirin. The Committee reconsidered the data from the manufacturer's and ERG's network meta-analyses and considered the manufacturer's additional indirect comparison comparing rivaroxaban with aspirin. The Committee concluded that it would not consider further the clinical effectiveness of rivaroxaban compared with aspirin or dabigatran etexilate.
The Committee considered the manufacturer's updated base-case analysis for rivaroxaban compared with warfarin for the licensed population. The Committee noted the ERG's comments on the manufacturer's updated cost-effectiveness analyses and the ERG's revised base-case analysis. The Committee noted that the manufacturer presented an ICER of 2870 per QALY gained (see section 3.25) and the ERG presented an ICER of 29,500 per QALY gained (see section 3.29). The Committee was made aware by both the manufacturer and the ERG that the difference in the ICERs resulted from two main factors. One was the manufacturer's inclusion in its updated analysis of a disutility value associated with warfarin treatment. The second was the different costs included by the manufacturer and ERG for warfarin monitoring (580 and 242 respectively).
The Committee discussed the disutility values used in the manufacturer's updated economic analyses. It noted that the manufacturer had used a small study of 57 patients to justify including a disutility associated with warfarin. The Committee acknowledged that comments received during consultation implied that warfarin was associated with disadvantages. However the Committee was mindful that the manufacturer had assumed that there was no disutility associated with rivaroxaban and had not provided any rationale for its exclusion. The Committee noted the comments from the ERG and consultees and commentators suggesting that there could be some disutility associated with newer anticoagulation therapy, including concerns about non-reversibility in the case of bleeding. However, the Committee noted that no specific evidence relating to disutility associated with anticoagulation therapy other than warfarin had been submitted by any consultees and commentators or by the ERG. The Committee therefore agreed that although it was appropriate to consider that there might be a disutility associated with warfarin treatment, it was not appropriate to assume that there was no disutility associated with rivaroxaban and other anticoagulant treatments. The Committee concluded that the disutility value used in the economic model for warfarin may have resulted in a bias in the manufacturer's economic analysis in favour of rivaroxaban.
The Committee discussed the costs associated with warfarin INR monitoring. The Committee noted that the manufacturer' model assumed an average annual anticoagulant monitoring cost of 580 per person in the year that treatment is first initiated and 535 once the person is stabilised on warfarin. The clinical specialists agreed that the annual cost of anticoagulant monitoring for each person treated with warfarin was likely to be lower than the manufacturer's estimate in clinical practice, but a precise estimate could not be given because costs varied considerably between people (for example, they are higher in those with poor INR control) and between centres. The Committee was aware of the uncertainty, but in the interests of consistency had requested that the manufacturer use 242 in its economic model, in line with what it had accepted for the ongoing appraisal of dabigatran etexilate for the same indication. However, the Committee noted the comments received during consultation, which suggested that significant numbers of people have difficulties managing their INR control and could therefore visit a clinic for monitoring up to once a week, making 30 visits a year not implausible. The Committee also noted the manufacturer's comments highlighting its concerns about the plausibility of a cost of 242 per person. The Committee therefore agreed that 242 per person was likely to be a conservative estimate of annual anticoagulant monitoring for warfarin if fixed costs were fully included, and that there was uncertainty about the cost of warfarin INR monitoring in clinical practice.
The Committee considered what the most plausible ICER would be for rivaroxaban compared with warfarin. It noted the ICERs of 2870 per QALY gained presented by the manufacturer (which included disutility associated with warfarin, and warfarin monitoring costs of 580) and 29,500 per QALY gained (which excluded disutility associated with warfarin, and used warfarin monitoring costs of 242) presented by the ERG. The Committee agreed that because there could be some degree of utility decrement associated with treatment, and the estimate of annual anticoagulation monitoring costs of 242 was likely to be conservative, the ICER for rivaroxaban compared with warfarin would be no more than 29,500 per QALY gained and would lie somewhere between 2870 and 29,500 per QALY gained. The Committee therefore concluded that the most plausible ICER for the whole population eligible for rivaroxaban was within the range that could be considered a cost-effective use of NHS resources.
The Committee considered whether there were any equalities considerations affecting population groups protected by equality legislation and concluded that there were no equality issues relating to this appraisal that needed addressing in the guidance.

# Summary of Appraisal Committee's key conclusions
TA256
Appraisal
                title:
                Rivaroxaban
                for
                the
                prevention
                of
                stroke
                and
                systemic
                embolism
                in
                people
                with
                atrial
                fibrillation
Section
Key
                conclusion
Rivaroxaban is recommended as an option within its licensed indication for the prevention of stroke and systemic embolism in adults with non-valvular atrial fibrillation.
The Committee recognised that decision about whether to start treatment with rivaroxaban should be made after an informed discussion between the clinician and the person about the risks and benefits of rivaroxaban compared with warfarin, and noting the limited direct trial evidence for people with a low risk of stroke (CHADS2 score of less than 2). For people who are taking warfarin, the potential risks and benefits of switching to rivaroxaban should be considered in light of their level of international normalised ratio (INR) control.
Current
                practice
Clinical need of patients, including the availability of alternative treatments
The current standard treatment for the prevention of stroke and systemic embolism in people with atrial fibrillation is warfarin. Because aspirin is less effective, it is used only in people for whom warfarin is unsuitable.
Warfarin is associated with a number of problems such as fear of having a stroke and anxiety about keeping the INR within the therapeutic range. In addition, people taking warfarin often worry about their level of INR control and they might find regular GP and hospital visits disruptive and inconvenient.
A substantial proportion of people taking warfarin have poorly controlled INR and are often not within the target therapeutic range at any one time.
The
                technology
Proposed benefits of the technology
How innovative is the technology in its potential to make a significant and substantial impact on health-related benefits?
The Committee recognised the potential benefits of alternatives such as rivaroxaban for people with atrial fibrillation, including the positive effect on quality of life of removing the restrictions and difficulties associated with taking warfarin.
What is the position of the treatment in the pathway of care for the condition?
Rivaroxaban would be used to prevent stroke and systemic embolism in people with atrial fibrillation and one or more risk factor for stroke.
Adverse reactions
The Committee noted the possible uncertainty in the results from the ROCKET-AF trial related to the relatively low proportion of time in therapeutic range of 55% in the warfarin arm of the trial, but concluded that the primary safety end point showed no statistically significant difference between rivaroxaban and warfarin.
Evidence
                for
                clinical
                effectiveness
Availability, nature and quality of evidence
The main clinical-effectiveness evidence came from one multicentre, double-blind randomised controlled trial. The ROCKET-AF trial compared rivaroxaban with dose-adjusted warfarin. The manufacturer also compared rivaroxaban with aspirin and dabigatran etexilate (110 mg or 150 mg twice a day) using a network meta-analysis in people for whom anticoagulation therapy was considered suitable.
The Committee also noted the additional indirect comparison submitted by the manufacturer during consultation comparing rivaroxaban with aspirin.
Relevance to general clinical practice in the NHS
The Committee concluded that the results of the ROCKET-AF trial were generalisable to UK clinical practice. However the Committee also agreed that when treatment with rivaroxaban is being considered, clinicians and patients should be aware that there is limited direct evidence available from the ROCKET-AF trial on the efficacy of rivaroxaban in people with a baseline CHADS2 score of less than 2.
Uncertainties generated by the evidence
The Committee noted that there were differing opinions among consultees and commentators on the generalisability of the ROCKET-AF trial to UK clinical practice.
The Committee agreed that the clinical-effectiveness estimates for rivaroxaban compared with dabigatran etexilate obtained from the network meta-analyses were unreliable
Are there any clinically relevant subgroups for which there is evidence of differential effectiveness?
The Committee heard from the manufacturer that rivaroxaban would be indicated for atrial fibrillation in people with one or more risk factors for stroke, which equates to a CHADS2 score of 1 or more. The Committee noted that the European Medicines Agency had stated in the 'European public assessment report' for rivaroxaban that efficacy results were essentially consistent in important subgroups, such as different CHADS2 scores (CHADS2 scores 2 to 6).The Committee accepted that, given the broad spectrum of risk covered by the licensed indication for rivaroxaban, there was no plausible reason to expect that the results of ROCKET-AF would not translate to people with a lower CHADS2 score.
Estimate of the size of the clinical effectiveness including strength of supporting evidence
The Committee was aware that primary objective of the ROCKET-AF was to establish non-inferiority of rivaroxaban versus warfarin.
Evidence
                for
                cost
                effectiveness
Availability and nature of evidence
The manufacturer developed a Markov model that compares rivaroxaban (20 mg once a day) with warfarin (adjusted dose warfarin at 4.5 mg once a day, target INR 2.5, range 2.0 to 3.0), aspirin (150 mg once a day), dabigatran etexilate (110 mg to 150 mg twice a day) and no treatment.
The Committee considered the manufacturer's updated base-case analysis for rivaroxaban compared with warfarin for the licensed population and the ERG's comments on the manufacturer's updated cost-effectiveness analyses and the ERG's revised base-case analysis.
Uncertainties around and plausibility of assumptions and inputs in the economic model
The Committee noted that both the manufacturer and ERG identified the costs associated with warfarin INR monitoring as a major factor affecting the cost-effectiveness estimate in the model.
The Committee noted that the manufacturer had assumed an average annual anticoagulant monitoring cost of 580 per person when treatment is first initiated and 535 once stabilised on warfarin. The Committee had in the interests of consistency requested that the manufacturer use 242 in its economic model, in line with what it had accepted for an ongoing appraisal of dabigatran etexilate for the same indication. The Committee agreed that the estimate of annual anticoagulant monitoring cost of 242 per person for warfarin was likely to be conservative if fixed costs were fully included, and that there was uncertainty about the cost of warfarin INR monitoring in clinical practice.
Incorporation of health-related quality-of-life benefits and utility values
Have any potential significant and substantial health-related benefits been identified that were not included in the economic model, and how have they been considered?
The Committee noted the comments from the ERG and consultees and commentators suggesting that there could be some disutility associated with newer anticoagulation therapy, including concerns about non-reversibility in the case of bleeding. However, the Committee noted that no specific evidence relating to disutility associated with anticoagulation therapy other than warfarin had been submitted by any consultees and commentators or by the ERG. The Committee therefore agreed that although it was appropriate to consider that there might be a disutility associated with warfarin treatment, it was not appropriate to assume that there was no disutility associated with rivaroxaban and other anticoagulant treatments.
Are there specific groups of people for whom the technology is particularly cost effective?
None were identified.
What are the key drivers of cost effectiveness?
In the ERG's view the manufacturer's base-case model is driven by the cost of anticoagulation monitoring rather than the differential effectiveness of rivaroxaban and warfarin.
The Committee noted that the manufacturer's model assumed an average annual anticoagulant monitoring cost of 580 per person in the year that treatment is first initiated and 535 once the person is stabilised on warfarin. The clinical specialists agreed that the annual cost of anticoagulant monitoring for each person treated with warfarin was likely to be lower than the manufacturer's estimate in clinical practice.
Most likely cost-effectiveness estimate (given as an ICER)
The Committee considered the most plausible ICER for rivaroxaban compared with warfarin. It noted the ICERs of 2870 per QALY gained presented by the manufacturer (which included disutility associated with warfarin, and warfarin monitoring costs of 580) and 29,500 per QALY gained (which excluded disutility associated with warfarin, and used warfarin monitoring costs of 242) presented by the ERG.
The Committee agreed that because there could be some degree of utility decrement associated with treatment, and the estimate of annual anticoagulation monitoring costs of 242 was likely to be conservative, the ICER for rivaroxaban compared with warfarin would be no more than 29,500 per QALY gained and would lie somewhere between 2870 and 29,500 per QALY gained.
Additional
                factors
                taken
                into
                account
Patient access schemes (PPRS)
Not applicable.
End-of-life considerations
Not applicable.
Equalities considerations and social value judgements
No equalities issues were identified.