CONCLUDE Trial Design
The trial design and primary results of CONCLUDE (NCT03078478) have been previously published [11, 15]. In brief, CONCLUDE was a multinational, randomised, open-label, treat-to-target, active comparator-controlled trial. Eligible patients were adults with type 2 diabetes, who had been previously treated with a basal insulin with or without oral antidiabetic drugs (OADs; any combination of metformin, dipeptidyl peptidase 4 inhibitor, α-glucosidase inhibitor, thiazolidinedione and sodium–glucose cotransporter 2 inhibitor) at a stable dose, and who fulfilled at least one pre-defined criterion for hypoglycaemia risk. Patients (N = 1609) were randomly assigned 1:1 to receive degludec or glargine U300, both administered once daily with or without OADs. Within each treatment arm, patients were also randomised 1:1 to either morning or evening basal insulin administration. Any pre-trial OADs were continued at their pre-trial dose for the full trial duration, unless safety reasons necessitated a change.
The original 52-week CONCLUDE trial—a 16-week titration period followed by a 36-week maintenance period—was extended following a protocol amendment implemented in February 2018 (described in detail in [15]). Routine monitoring of blinded data identified an unusual pattern in the reporting of glycaemic parameters and hypoglycaemic events, raising patient safety concerns. Therefore, as a result of these concerns, patients were switched from the original glycaemic data collection system (MyGlucoHealth BG meter and electronic diary) to an Abbott BG meter and paper diary, which was used for the remainder of the trial. All patients had completed the 16-week titration period prior to the switch. A new 36-week maintenance period was included in the trial to accommodate these changes, preserve scientific integrity and ensure sufficient data collection for the confirmatory endpoints using the same glycaemic data collection system. On the basis of this new maintenance period, the total treatment period was up to 88 weeks. All analyses of CONCLUDE endpoints in the maintenance period considered the new maintenance period only. CONCLUDE was conducted in accordance with the provisions of the Declaration of Helsinki and the International Conference on Harmonisation Good Clinical Practice Guidelines. The CONCLUDE protocol was approved by the independent ethics committee or institutional review board at each trial centre and written informed consent was obtained from each patient before any trial-related activities.
Cost-Effectiveness Model Overview
A published, transparent model developed in Microsoft Excel [16] was used to evaluate the short-term cost-effectiveness of degludec compared with glargine U300 in terms of costs (2018 EUR) and QALYs from a Dutch societal perspective. This short-term cohort model with a single annual cycle was informed by data on clinical outcomes from the CONCLUDE trial population, and captured hypoglycaemia rates (non-severe daytime, non-severe nocturnal and severe) and insulin dosing (Fig. 1). The model utilised hypoglycaemia data collected in the 36-week maintenance period of CONCLUDE to allow the comparison of hypoglycaemia rates when glycaemic control and insulin dose were stable, and to reduce potential carryover effects from prior treatment regimens.
Treatment Effects
Treatment differences (between degludec and glargine U300) were estimated using hypoglycaemia rate and insulin dose ratios from regression analyses of data from the CONCLUDE trial population. To avoid any overlap between hypoglycaemia definitions, and therefore the potential to overestimate costs, overall symptomatic hypoglycaemic events in the maintenance period of CONCLUDE were categorised into mutually exclusive groups for modelling purposes and in alignment with other CEAs of degludec (e.g. [17, 18]): non-severe daytime, non-severe nocturnal and severe hypoglycaemia. In the present study, non-severe hypoglycaemia was defined as BG < 3.1 mmol/L (56 mg/dL) with symptoms. Non-severe hypoglycaemic events were categorised as daytime (occurring between 06:00 and 00:00 or the time was unknown), or nocturnal (occurring between 00:01 and 05:59). Severe hypoglycaemia was defined as an event requiring third-party assistance [12].
Analyses of insulin dose, non-severe daytime hypoglycaemia and non-severe nocturnal hypoglycaemia, informed by CONCLUDE, were conducted post hoc; severe hypoglycaemia was analysed as per the pre-specified model in the CONCLUDE trial [11]. Hypoglycaemia endpoints were analysed using a negative binomial model with a log link. The logarithm of the time period in which a hypoglycaemic event was considered treatment emergent as offset. The model included treatment, number of OADs, region, gender and dosing time as fixed factors, and age as a covariate. Missing data were imputed by treatment arm using a Poisson model. End-of-trial basal insulin dose (units/kg) was analysed using a mixed model for repeated measures with an unstructured covariance matrix. The model included treatment, number of OADs, region, gender and dosing time as fixed factors; in addition to age, the logarithm of baseline insulin dose and interactions between visit and all exploratory variables as covariates.
Rate and dose ratios from regression analyses were applied to hypoglycaemia rates and insulin dosing observed in the glargine U300 treatment arm in CONCLUDE to derive model inputs for the degludec simulation arm. Treatment effects were only applied where there was a statistically significant difference between treatment arms; otherwise, hypoglycaemia rates and doses from the glargine U300 treatment arm were modelled in both simulation arms (Table 1).
Table 1 Input parameters: clinical outcomes from the CONCLUDE trial and costs and utilities Costs, Utilities and Time Horizon
Treatment unit costs were based on Dutch list prices (Table 1) [19]. It was assumed that patients administered one basal injection per day, with a new needle and self-measured blood glucose test strip per injection in both simulation arms. Insulin costs were captured as the unit cost multiplied by the mean annual dose. Hypoglycaemia costs and disutilities were derived from the literature, and the costs were inflation-adjusted to 2018 EUR using the Dutch Consumer Price Index (Table 1) [20].
Hypoglycaemia costs were calculated as the sum of costs associated with healthcare, informal care (from informal caregivers) and lost productivity, using data from Dutch patients included in the Global Hypoglycaemia Assessment Tool study and unit costs derived from the Dutch costing manual [21,22,23]. Costs associated with productivity loss were not included in estimates for severe hypoglycaemia given that the advanced mean baseline age of the CONCLUDE patient population suggests that a large proportion of the patients would be outside the labour market. Hypoglycaemia disutilities were applied by multiplying an annualised disutility by the annual event rate; there were multiple disutilities (for each hypoglycaemia definition). Treatment costs relating to the use of OADs were not included in this analysis as they were assumed to be similar across simulation arms as a result of randomisation and continuation of any pre-trial OADs at the pre-trial dose.
A 1-year time horizon was selected to avoid assumptions regarding the longevity of clinical effects and as a result of the treat-to-target trial design of CONCLUDE, which aimed to achieve glycaemic parity across treatment arms and, thus, obviates the utility of long-term modelling based on differences in glycaemic control. Consequently, the present analysis did not consider the significant, but not clinically relevant, difference in end-of-treatment glycaemic control in favour of degludec (estimated treatment difference − 0.10% 95% CI [− 0.18; − 0.02]) [11]. The modelled time horizon represents time at maintenance treatment—at relatively stable insulin dose and glycaemic control—and, therefore, does not necessarily represent the first year of treatment and can be extended by additional years, assuming that patients remain at steady state.
Sensitivity Analyses
One-way deterministic sensitivity analyses were conducted to identify key drivers of outcomes in the base case analysis. Sensitivity analyses explored alternative baseline rates, costs and disutilities for hypoglycaemia. Additional sensitivity analyses were performed varying treatment effects for insulin dosing and hypoglycaemia rates, including those where hypoglycaemia rate ratios were applied regardless of significance and those informed by hypoglycaemia rates observed over the total treatment period of CONCLUDE.
A probabilistic sensitivity analysis (PSA) was conducted to quantify the effect of statistical uncertainty around all relevant stochastic input parameters used in the model. Uncertainty was captured using log-normal distributions (rate and dose ratios) around model parameters, informed by standard errors from CONCLUDE analyses (Table 1). PSA outcomes were based on 1000 model iterations sampling from all modelled distributions in each iteration without capturing covariance. For each simulated set of values, an estimate of incremental costs and incremental QALYs was obtained.