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

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Economic model
TABLE 85 Treatment sequences compared in economic model
Treatment sequences 1 2 3 4 5 6
1st line MPH MPH ATX ATX DEX DEX
2nd line ATX DEX MPH DEX MPH ATX
3rd line DEX ATX DEX MPH ATX MPH
4th line No treatment No treatment No treatment No treatment No treatment No treatment
×3 to represent each formulation of MPH = 18
×2 to include combination therapy = 36
+ no treatment = 37
Drug 1
Tolerate
Intolerable sideeffects
reduction in the number of strategies aids
interpretation of the model results. The
consequence is that by removing a number of
strategies, the decision uncertainty is
underestimated.
Each treatment sequence is composed of a
formulation of MPH (IR-MPH or ER-MPH8 or
ER-MPH12), DEX and ATX, followed by no
treatment last in sequence. This results in 18
treatment strategies to be considered in the
model, all of which can be compared on the basis
of pharmacotherapy only, or as part of
combination therapy. In addition, there is a no
(drug) treatment option, so there are 37 sequences
for comparison. Table 85 provides more
information on the sequences for comparison.
Model structure
Upon entering the model, patients begin titration
on the first-line treatment. This titration period is
assumed to last for 1 month. The purpose of this
titration period is to determine the optimal dose,
in terms of adverse events and response to
treatment. During the titration period, patients
Response
No response
Drug 2
Continue on
treatment
Drug 2
FIGURE 22 Representation of economic model structure. Once all treatment options are exhausted, patients are assumed to remain
non-responders on no treatment.
can withdraw from treatment if they experience
intolerable side-effects and they are then assumed
to enter the titration period for the next drug in
sequence. The model assumes that patients
tolerating treatment will continue with that
treatment if they experience a response. Those
patients who do not respond to treatment by the
end of the titration period are assumed to move
to titration for the next treatment in sequence. In
the base case analysis, it is assumed that
responders remain on therapy and continue to be
responsive for the rest of the year. Another
assumption of the model is that, although
responders may experience side-effects with
treatment, these will be relatively minor and
tolerable; hence they will not develop intolerable
side-effects beyond the titration period. This
assumption was considered reasonable following
consultation with a clinical expert. In summary, in
the base case analysis, patients only withdraw
owing to side-effects during the titration period,
and patients are moved to the next treatment in
sequence if they fail to respond by the end of the
titration period. Figure 22 provides a simple
summary of the model structure.