Stopping Clinical Trials Early Often Exaggerates Treatment Effects

An international study of nearly 100 clinical trials that were stopped early due to positive treatment effects has found that many of those effects were exaggerated. The authors of the study – published the Journal of the American Medical Association – recommend that researchers resist pressures to end clinical trials early and continue trials for longer periods before even considering premature termination.

“Our research shows that in most cases early stopping of clinical trials resulted in misleading estimates of treatment effects. These misleading estimates are likely to result in misguided decisions about the trade-off between risks and benefits of a therapy,” Victor Montori, MD, Mayo Clinic endocrinologist and corresponding author of the study, said in a new release. “On average, treatments with no effect would show a reduction in relative risk of almost 30% in stopped early trials. Treatments with a true relative risk reduction of 20% would show a reduction of [more than] 40%.”

The clinical trials that Montori and colleagues studied were ended early because of a convincing – and usually large – apparent difference between an experimental treatment and an existing standard therapy. The studies were ended so participants taking a placebo or less effective medications could also take the studied drug. It usually also allows physicians to prescribe the therapy sooner because it will reach the market earlier.

The researchers examined 63 medical questions regarding 91 truncated trials and compared them to 424 comparable trials that were not stopped early. Results showed that the studies that were stopped had exaggerated or misleading treatment effects. Those misleading findings are often compounded downstream because researchers are less likely to return to the topic after what is perceived as a significant successful finding.

The authors recommend that researchers use restraint and truncate clinical trials only near the end of a study and then only with “a good reason.” Otherwise, patients and physicians will be making treatment choices based on inaccurate information, or worse, opting for one treatment when another may be more appropriate, Montori said.

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