The manufacturer based its cost-effectiveness analysis on the York model used in 'Etanercept and efalizumab for the treatment of adults with psoriasis' (NICE technology appraisal guidance 103 [TA 103]).
In the manufacturer's base-case analysis, the incremental cost per quality-adjusted life year (QALY) gained for adalimumab compared with supportive care was 30,500 pounds sterling. Etanercept given continuously was dominated by adalimumab (that is, adalimumab had greater effectiveness and lower costs than etanercept), and etanercept given intermittently (assumed to be 88% of the cost of continuous etanercept) and efalizumab were ruled out on the grounds of extended domination (that is, the incremental costs per QALY gained were higher than for adalimumab even though either the cost or effectiveness was more favourable).
The manufacturer's base-case analysis included only people whose psoriasis had a substantial effect on their quality of life, as indicated by a baseline dermatology life quality index (DLQI) score greater than 10. The manufacturer conducted a sensitivity analysis for people with milder forms of psoriasis (baseline DLQI less than or equal to 10) and this increased the incremental cost per QALY gained for adalimumab compared with supportive care from 30,500 pounds sterling (baseline DLQI greater than 10) to 80,100 pounds sterling (baseline DLQI less than or equal to 10).
The manufacturer carried out further sensitivity analyses to test key assumptions in the model. Changing the number of hospital inpatient days assumed to be avoided by using a biological therapy instead of supportive care had a large impact on the results. Changing the assumption used in the base-case analysis (21 hospital inpatient days avoided per year) to 0 days and 39 days was associated with incremental costs per QALY gained of 60,600 pounds sterling and 4800 pounds sterling, respectively, compared with supportive care.
Changing the assumption regarding the cost of intermittent etanercept from 88% of the cost of continuous etanercept to 74% (the figure used in the York model) reduced the incremental cost per QALY gained for intermittent etanercept compared with supportive care from 37,300 pounds sterling to 27,600 pounds sterling.
The Evidence Review Group (ERG) ran the manufacturer's model, changing the assumption for the cost of intermittent etanercept to the value used in the York model (74% of the continuous etanercept cost); this resulted in 27,300 pounds sterling per QALY gained for intermittent etanercept compared with supportive care and 36,700 pounds sterling per QALY gained for adalimumab compared with intermittent etanercept. Changing the assumption for the cost of intermittent etanercept did not alter the cost effectiveness results for adalimumab compared with continuous etanercept; adalimumab continued to have greater effectiveness and lower costs than etanercept.
The ERG performed a probabilistic sensitivity analysis, re-running the manufacturer's model using different assumptions for treatment with intermittent etanercept (74% of the continuous etanercept dose used to calculate costs rather than 88%) and infliximab (three infusions in the trial period rather than four). The ERG found that adalimumab had a 16% probability of being cost effective at a threshold of 30,000 pounds sterling per QALY, compared with 46% estimated by the manufacturer.
The Committee noted that in the manufacturer's base-case analysis using indirect comparisons, etanercept given continuously was dominated by adalimumab (that is, adalimumab had greater effectiveness and lower costs) and etanercept given intermittently (assumed to be 88% of the cost of continuous etanercept) was ruled out on the grounds of extended domination (that is, the incremental cost per QALY gained was higher even though either the cost or effectiveness was more favourable).
The Committee noted that the manufacturer's base-case analysis included an estimate of utility for the use of intermittent etanercept that assumed a disutility related to the associated 'gaps' in therapy. The Committee was concerned, however, that the dose of intermittent therapy used to calculate costs (88% of the continuous etanercept dose) was estimated from US data and was inconsistent with the dose assumed in TA103 (74%).The Committee noted that assumptions regarding the yearly dose for etanercept based on an intermittent dosing schedule had a large impact on the results, and it agreed that the assumptions used should be consistent with those applied in TA103. It also noted the manufacturer's sensitivity analysis, where the assumption regarding the cost of intermittent etanercept was changed to 74% of the cost of continuous etanercept (as in TA103); the resulting incremental cost per QALY gained for intermittent etanercept compared with supportive care (27,600 pounds sterling) was consistent with the value calculated by the ERG (27,300 pounds sterling) in its re-analysis of the manufacturer's model. In addition, the Committee noted that the ERG had also estimated the incremental cost per QALY gained for adalimumab compared with intermittent etanercept, which was 36,700 pounds sterling.
The Committee concluded that adalimumab should be recommended as a treatment option only for people with severe plaque psoriasis when standard systemic therapies have failed.
Refer to Sections 3 and 4 of the original guideline document for details of the economic analyses provided by the manufacturer, the ERG comments, and the Appraisal Committee considerations.
