Halting clinical trials early because of positive results may lead to exaggerations of how effective those treatments actually are, according to an international study of nearly 100 such trials. The authors of the study—published in the current issue of the Journal of the American Medical Association—recommend that researchers resist pressures to end clinical trials early and continue them 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,” says Victor Montori, Mayo Clinic endocrinologist and corresponding author of the study. “These misleading estimates are likely to result in misguided decisions about the trade-off between risks and benefits of a therapy.”

 

On average, treatments with no effect would show a reduction in relative risk of almost 30 percent in trials stopped early, Montori says. Treatments with a true relative risk reduction of 20 percent would show a reduction of more than 40 percent, he says.

 

The clinical trials that the researchers 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.

 

Montori says almost everyone involved benefits from a trial ending early because it usually allows the therapy to reach the market earlier, but patients may suffer because they could end up receiving a therapy on the basis of misleading information about its benefits.

 

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—especially smaller trials of a few hundred participants—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 very good reason.” Otherwise, says Montori, patients and physicians will be making treatment choices based on inaccurate information, or worse, opting for one treatment when another may be more appropriate.