Even after investigators carefully design a study protocol, obtain IRB approval, and successfully recruit participants, it does not mean the clinical trial will be completed as intended. “There are several reasons to stop a clinical trial early. Often, these reasons differ depending on the phase of trial being conducted,” according to Lisa M. Lee, PhD, MA, MS, associate vice president for research and innovation at Virginia Tech.
Some trials end early due to safety concerns. The Data and Safety Monitoring Board may find a severe or unexpected safety outcome. Lack of enrollment is another reason for stopping a trial; some researchers struggle to find enough eligible participants. “To prevent this, most study protocols require a researcher to describe how they will meet their enrollment goals,” Lee says.
Researchers should consider the size of the population who are living with the condition studied and meet the eligibility criteria. “Once all of the eligibility criteria are applied, a researcher could end up with a lot smaller group from which to recruit,” Lee notes.
Then, investigators must take into account how many of those people, once enrolled, might end up discontinuing participation. Sometimes, participants decide they cannot or do not want to continue. “Careful planning can reduce the chance of closing a study due to lack of enrollment,” Lee offers.
Some participants do not complete all the research tasks, leaving scientists with incomplete data. That could mean the participant’s data could be excluded. “It is helpful for researchers to look at retention rates from other similar studies,” advises Lee, adding this gives a practical estimate of the percentage of eligible participants who actually will complete the study.
Other studies end early because they show great benefit, before they complete enrolling the planned number of participants. “Unfortunately, stopping for this reason can be a mistake,” Lee warns. “Large early effects usually turn out to be much more attenuated once all the data are in, resulting in false inflation of the results.”1
Stopping a clinical trial might be unavoidable. If safety is a concern, it might be best to end the research. “IRBs must consider whether the potential study harms are worth the potential benefit of the knowledge that the study will produce,” Lee says.
To produce beneficial knowledge, the authors must use scientifically sound methods and conduct statistically sound data analysis. There must be enough participants to ensure any findings (positive or negative) are statistically valid. “This is why it is important for IRBs to review the sample size and power estimates in all study protocols,” Lee stresses.
If an underpowered study with too few participants goes ahead, its findings will be meaningless. All the risk to participants will have been for nothing. “We would call this an unethical study,” Lee says.
Regardless of the reason for stopping a trial early, researchers are ethically obligated to participants. “Research participants consent to take on risk for the benefit of others, not for their own benefit,” Lee explains.
If a trial ends prematurely, researchers should tell participants. Investigators also must ensure any risks participants accepted are mitigated to the fullest extent possible. “Mitigation strategies might include changing to an already-approved treatment or intervention, moving the placebo group to an approved treatment, or continued monitoring,” Lee offers.
REFERENCE
1. Bassler D, Montori VM, Briel M, et al. Early stopping of randomized clinical trials for overt efficacy is problematic. J Clin Epidemiol 2008;61:241-246.
Research participants consent to take on risk for the benefit of others, not for their own benefit. If a trial ends prematurely, researchers should tell participants. Investigators also must ensure any risks participants accepted are mitigated to the fullest extent possible.
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