Optimising Accrual: How Evidence From Other Studies Can Influence Enrolment in Yours

We all know the importance of optimising participant enrolment in clinical trials by now.

It’s fairly obvious isn’t it?

The process of identifying and obtaining participants for a study is a major determinant of a clinical trials success and subsequent commercial relevance. It is therefore a consideration that demands focus, priority and proactive implementation from trial conception to completion.

Without study participants there really is no clinical trial and with too few participants we run the risk of possibly proving nothing at all, (or nothing clinically worthwhile anyway). Researchers and their funding sources can potentially waste numerous efforts and (expensive) resources, including valuable time in which other developing or comparable therapies can affect the population under investigation and render the study intervention superfluous or even ethically unviable.

We must consider the potential impact extending recruitment periods has over time as new evidence from comparable or related studies may influence the appropriateness of continuing one’s own trial by indicating that continual recruitment is inappropriate or by increasing study non-compliance (in instances where participants ‘drop-out’ of study treatment in favour of the new comparator) or forcing trial mangers to expensively redesign studies to maintain statistical power and significance.

We have to ask ourselves, if new evidence arises during the time it has taken to enrol our intended sample that suggests our hypothesis has already been proven, is it clinically worthwhile or ethical to continue? What if the evidence suggests our intervention is inferior or if the therapy has an unacceptable safety profile? We may have to cease the whole study. If excessive attrition in our study sample occurs or accrual is too slow, the initial power calculations will be have inaccurately applied for this new sample total, analysis is limited and any inferences made as to the effect of the intervention will be potentially inconsequential.

It is fair to say that in light of new evidence, we must consider continuing recruitment and enrolment in a study only if we can be assured that:

Important clinical questions remain unanswered.
There is an ethical basis for continuation (including opportunity for individual patients to receive treatment)
Trial mangers and researchers have the ability (resources/statistical power) to answer these revised questions.

There is an obvious need to balance the risks and benefits of people participating in trial with knowledge gained for helping future patients to which the population is representative of. If clear evidence suggests that any new treatment is better than current study intervention then we should not continue the trial or recruitment.

Dom Bailey