StATS: Cumulative meta-analysis (March 11, 2005).
This figure below, published in
shows cumulative meta-analysis, which is the cumulated effects over time of studies in the use of erythropoietin (EPO) to treat cancer related anemia. The outcome variable, the odds ratio for whether a patient requires transfusion, showed a significant benefit for EPO and that sufficient evidence had already accumulated by 1995. If such a meta-analysis had been performed back then, there would have been no need to run the additional trials. These redundant trials are bad because they wasted scarce research dollars on a topic where sufficient information had already been accumulated to answer the research question. They are also bad because half of the patients in these post-1995 trials received no treatment or placebo, even though there was enough evidence at that time to show that this is an inferior option.
There has been a suggestion that any protocol submitted to an Institutional Review Board (IRB) should include a systematic overview or meta-analysis of the previous research (see Chalmers 1996), rather than just a simple literature review, to prevent future IRBs from making the same mistake of those that approved the post-1995 studies of EPO. In some situations, that is definitely overkill, but it is a suggestion worth serious consideration in other circumstances.
Since BMC Cancer is published with an open access license, I can freely reproduce this image without getting permission, as long as I cite the source. I try to preferentially cite such resources because they make it easy to include their content on my web pages and in my teaching.
This page was written by Steve Simon while working at Children's Mercy Hospital. Although I do not hold the copyright for this material, I am reproducing it here as a service, as it is no longer available on the Children's Mercy Hospital website. Need more information? I have a page with general help resources. You can also browse for pages similar to this one at Category: Systematic overviews.