Many positive treatment effects are exaggerated in clinical trials that are stopped early due to encouraging results, a new study has found.
In a comparison of 91 truncated trials with 424 comparable full-length trials, researchers found that the trials that ended early -- in particular, smaller studies -- reported exaggerated or misleading treatment effects.
"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," study corresponding author Dr. Victor Montori, a Mayo Clinic endocrinologist, said in a news release.
"On average, treatments with no effect would show a reduction in relative risk of almost 30 percent in stopped early trials. Treatments with a true relative risk reduction of 20 percent would show a reduction of over 40 percent," Montori said.
Almost everyone -- doctors, researchers, funding sources, drug makers, medical journals -- benefits from a clinical trial ending early, Montori noted. But patients don't benefit because they may end up receiving a therapy on the basis of misleading information about its benefits.
Montori and colleagues said that researchers must resist pressure to end clinical trials early and continue trials until they're nearly completed before even considering an early halt.