Clinical Trials

Clinical Trials: A Practical Guide ■❚❙❘ConclusionClinical trials are conducted to identify whether the use of a specific treatmentwould be beneficial for populations of patients with a specific disease. In addition,it is important to consider how, within this group, patients with specificcharacteristics will respond to the treatment. Subgroup analyses allow us toexplore the relationship of characteristics to treatment effect. There are, however,a variety of pitfalls and limitations with such analyses, and their results should notbe over-interpreted, particularly without rational biological explanations.Interaction tests should also be performed, rather than simple comparisons alone.With these reservations, well-conducted and predefined analyses provide insightsto allow better-informed treatment decisions for individual patients.References1. Fisher B, Redmond C, Brown A, et al. Influence of tumour estrogen and progesteronereceptor levels on the response to tamoxifen and chemotherapy in primary breast cancer.J Clin Oncol 1983;1:227–41.2. Bakhai A. Practical issues in trial design. Part 3: confidence intervals. Clinical Researcher2001;1(6):46–7.3. Mills JL. Data torturing. N Engl J Med 1993;329:1196–9.4. Cerrito PB. Subgroup analysis. In: Chow SC. Encyclopedia of Biopharmaceutical Statistics.New York: Marcel Dekker, 2000;497–507.5. Randomised trial of intravenous streptokinase, oral aspirin, both, or neither among 17,187 casesof suspected acute myocardial infarction. ISIS-2 (Second International Study of Infarct Survival)Collaborative Group. Lancet 1988;2;349–60.6. Yusuf S, Wittes J, Probstfield J, et al. Analysis and interpretation of treatment effectsin subgroups of patients in randomized clinical trials. JAMA 1991;266:93–8.7. Assmann SF, Pocock SJ, Enos LE, et al. Subgroup analysis and other (mis)uses of baselinedata in clinical trials. Lancet 2000;355:1064–9.271