Randomized clinical trials (RCTs) define the efficacy of new cancer treatments and drive changes in clinical practice. Although the role of RCTs in generating knowledge is universally accepted, the often-cited benefits of trial participation for individual patients is open for debate. The trial effect is composed of potential gains offered by the new treatment (ie, the treatment effect) and potential gains offered by virtue of participating in the trial itself (ie, the participation effect). Gains due to treatment effect can only be realized by patients in an experimental group that proves to be superior to standard care, while participation effect can be experienced by participants in both groups.
