LETTER
Megatrials for Clinical Decision Making
Karl-Ludwig Resch, MD, PhD
1 October 1996 | Volume 125 Issue 7 | Page 621
TO THE EDITOR:
Borzak and Ridker [1] highlight some established strengths and weaknesses of meta-analyses. In contrast to Chalmers [2] and Charlton [3], however, they provide a much less balanced view of large-scale randomized, controlled trials.
Is it helpful to use examples of megatrials with sample sizes of 60 000 to 70 000 patients to advocate megatrials, when respective meta-analyses include scarcely 2000 patients? In fact, the two examples with comparable patient numbers (although several times larger than 2000) showed no substantial differences between the two approaches. If anything, one could conclude that evidence from more cases is more reliable.
It is also common wisdom that the existing evidence should be considered when designing a clinical trial. I disagree, however, that a meta-analysis should exclusively be viewed as "hypothesis-generating" [1]. This proposal denies the fact that, however biased, a high-quality meta-analyses ("systematic review" [4]) quantitatively summarizes the existing evidence. What could be a better basis for a clinician's treatment decision at the time it must be made?
We will never have enough expertise, resources, or patients to conduct large-scale randomized, controlled trials on every topic (trials that, one could argue, would then have to be confirmed by at least one other independent trial of similar size).
The strength of individual large-scale randomized, controlled trials should not be overestimated. For practical purposes (that is, the clinical treatment decision), clinicians should practice evidence-based medicine, for which meta-analyses can be an extremely helpful tool. This approach is both more reliable than a clinician's personal experience alone [5] and more beneficial for a given patient than a clinician's disregard for the evidence from meta-analyses while awaiting the results of larger randomized, controlled trials.
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Author and Article Information
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University of Exeter, Exeter EX2 4NT, United Kingdom
1. Borzak S, Ridker PM. Discordance between meta-analyses and large-scale randomized, controlled trials. Examples from the management of acute myocardial infarction. Ann Intern Med. 1995; 123:873-7.
2. Chalmers TC. Antioxidants and cardiovascular disease: why do we still not have the answers? [Editorial] Ann Intern Med. 1995; 123:887.
3. Charlton BG. Mega-trials: methodological issues and clinical implications. J R Coll Physicians Lond. 1995; 29:96-100.
4. Sackett DL, Oxman AD, eds. The Cochrane Collaboration Handbook. 1996; Cochrane Collaboration Homepage: http://hiru.mcmaster.ca/cochrane/default.htm.
5. Antman EM, Lau J, Kupelnick B, Mosteller F, Chalmers TC. A comparison of results of meta-analyses of randomized controlled trials and recommendations of clinical experts: treatments for myocardial infarctions. JAMA. 1992; 268:240-8.
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