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SMART Designs for Developing Dynamic Treatment Regimes. S.A. Murphy Symposium on Causal Inference Johns Hopkins, January, 2006. Outline. Why Dynamic Treatment Regimes? Why SMART experimental designs? Design Principles and Analysis of Balanced Designs.
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Symposium on Causal Inference
Johns Hopkins, January, 2006
Treatment of alcohol dependence. Goal is to reduce drinking.
Following graduation from the intensive outpatient program the patient is prescribed naltrexone. The patient is monitored weekly over the next two months. If the patient experiences 2 or more heavy drinking days during this period and is nonadherent then the patient’s medication is augmented by CBI. If the patient experiences 2 or more heavy drinking days during this period and is adherent then the patient’s medication is switched to acamprosate.If the patient is able to make the entire 2 months with 1 or no heavy drinking days then the patient is continued on naltrexone and the patient is provided telephone disease management.
What is a sequential multiple assignment randomized trial (SMART)?
These are multi-stage trials; conceptually a randomization takes place at each stage.
Goal is to inform the construction of a dynamic treatment regime.
Negative synergies: An initial treatment may produce a higher proportion of responders but also result in side effects that reduce the effectiveness of subsequent treatments for those that do not respond. Or the burden imposed by this initial treatment may be sufficiently high so that nonresponders are less likely to adhere to subsequent treatments.
Positive synergies: A treatment may not appear best initially but may have enhanced long term effectiveness when followed by a particular maintenance treatment. Or the initial treatment may lay the foundation for an enhanced effect of subsequent treatments.
When evaluating and comparing initial treatments we need to take into account the effects of the secondary treatments thus SMART
Subjects who will enroll in, who remain in or who are adherent in the trial of the initial treatments may be quite different from the subjects in SMART.
Why not use theory, clinical experience and expert opinion to construct the dynamic treatment regime and then compare this regime against an appropriate alternative in a confirmatory randomized trial?
The alternative may be the same regime but with one component altered.