A systematic review and economic model of the effectiveness and ...

Probability cost-effective
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is reasonable, then strategies 13–18 are no longer
relevant, and the optimal treatment strategy is
then number 7 (first-line IR-MPH, second-line
DEX, third-line ATX). Strategy 7 does not
dominate all the remaining alternatives. Strategy 9
(first-line ER-MPH12, second-line DEX, third-line
ATX) is more costly and more effective, with a cost
per QALY gained of £5,595,829 compared with
strategy 7. If society were willing to pay £30,000
per additional QALY, strategy 7 would have an
84% probability of being most cost-effective.
Again, this probability only includes uncertainty
between treatment strategies featuring three active
treatments. There is less uncertainty than when
DEX is considered suitable as first-line therapy
because there are six fewer treatment strategies
being compared (13 compared with 19).
Medication as part of combination
therapy
The trials used to estimate response rates for the
base case included a trial comparing IR-MPH
alone with IR-MPH combined with BT. This trial
was used to estimate the relative change in
response rate of adding BT to medication. This
relative effect was then applied to all of the drug
treatments, yielding the same relative change in
response rate across all treatments. This
simplification was necessary as trials were not
available assessing combination therapy with each
of the relevant drug comparators. Also, had such
trials been available, it is likely that the
© Queen’s Printer and Controller of HMSO 2006. All rights reserved.
Health Technology Assessment 2006; Vol. 10: No. 23
0 10,000 20,000 30,000 40,000 50,000 60,000
Willingness to pay per QALY (£)
FIGURE 23 CEACs for 19 strategies compared in the base case analysis
Strategy 13
behavioural component would differ between
trials, as highlighted in the section ‘Combination
therapy’ (p. 105). Hence this sensitivity
analysis represents a simplistic analysis of the
cost-effectiveness of drug therapy in combination
with BT.
The results of this sensitivity analysis indicate that
strategy 13 remains the optimal treatment
strategy. However, strategy 13 does not dominate
the strategies that include combination therapy.
This is because the drugs in combination with BT
are marginally more effective than when given
alone. By calculating the ICERs, according to the
rules of dominance and extended dominance, the
only alternative not ruled out is strategy 36
(combination therapy with first-line DEX, secondline
ATX, third-line ER-MPH8). The cost per
QALY gained with strategy 36 compared with
strategy 13 is £1,241,570, hence combination
therapy does not appear cost-effective in this
sensitivity analysis. Increasing the number of
strategies from 19 to 37 increases the decision
uncertainty. If society were willing to pay £30,000
per additional QALY, strategy 13 has a 40%
probability of being the optimal strategy
(compared with 60% in the base case excluding
combination therapy).
If DEX is not suitable as a first-line therapy, then
strategy 7 (first-line IR-MPH, second-line DEX,
third-line ATX) is the optimal treatment strategy.
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