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10class.wk10 - PubH 7-420 Clinical Trials: Readings for...

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PubH 7-420 Clinical Trials: Readings for Week 10 1. Friedman, Furberg, and DeMets. Fundamentals of Clinical Trials , Chapter 16. Supplemental Reading/References 2. Yusuf S, Wittes J et al. Analysis and interpretation of treatment effects in subgroups of patients in randomized clinical trials. JAMA , 266:93-38, 1991. 3. Bulpitt CJ. Subgroup Analysis. Lancet 31-34, 1988. 4. Lakakos S. The challenge of subgroup analyses – reporting without distorting. NEJM 354:1667-1669, 2006. 5. Oxman AD, Guyatt GH. A consumer's guide to subgroup analysis. Ann Int Med 116:78-84, 1992. 6. Assmann SF, Pocock SJ, Enos LE, Kasten LE. Subgroup analysis and other (mis) uses of baseline data in clinical trials. Lancet 355:1064-1069, 2000. 7. Pocock SJ. Clinical trials. A practical approach, Chapter 14. 1
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SUBGROUP ANALYSIS Participants in clinical trials vary in terms of demographics, stage of disease, use of concomitant treatments and many other factors. This is true to a certain extent even in trials with strict eligibility criteria. If a specific treatment is much more effective in a subgroup of the population, it is important to know that and understand why. This thinking motivates subgroup analysis in clinical trials. There is usually interest in examining many subgroups because clinicians treat a variety of patients and a natural question is whether the treatment works similarly in all. There is also a temptation to try to find subgroups where the treatment works the best. If you examine several subgroups, there is a risk of finding subgroups that differ from one another by chance. A naive interpretation of subgroups is a cause of much confusion in the medical literature. Many clinical trialists think that subgroup analyses should not be performed -- the best estimate of an individual's response to treatment is the overall response (the response of the average patient). Others feel that subgroup analyses should only be performed by experienced investigators like themselves -- they are skeptical of everyone else's subgroup analyses. Federal guidelines will require all trials do some subgroup analysis (e.g., by gender and race). As a result of many NIH sponsored studies including predominantly white men, guidelines now mandate the inclusion of women and minorities in most NIH sponsored clinical trials. They state the following: "..when a Phase III clinical trial is proposed, evidence must be reviewed to show whether or not clinically important gender or race/ethnicity differences in the intervention effect are to be expected. This evidence may include, but is not limited to, data derived from prior animal studies, clinical observations, metabolic studies, genetic studies, pharmacology studies, and observational, natural history, epidemiology and other relevant studies." The guidelines state that if this evidence indicates that differences among subgroups in the effect of the intervention are likely, the planned trial must accommodate the differences: "For example, if men and women are thought to respond differently to an intervention,
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10class.wk10 - PubH 7-420 Clinical Trials: Readings for...

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