Randomised clinical trials provide the strongest evidence on the efficacy of surgical and chemotherapy treatments for ovarian cancer. Despite their value, recruitment to trials is often limited with only a small proportion of ovarian cancer patients receiving treatment as part of a clinical trial.

A systematic review and an observational study exploring barriers to participation in clinical trials in the UK were identified.^{136, 137} The systematic review found that patients who are more knowledgeable about the randomisation process are less likely to participate in trials.¹³⁷ This suggests that participation in trials might be improved by increasing awareness about the other benefits of being involved in a trial in addition to the possibility of receiving the experimental treatment. Evidence level 1++,3

The observational study explored recruitment to an individual trial in the UK and found that most people considered for trial inclusion did not meet inclusion criteria.¹³⁶ Participation by people eligible for the study was high as long as their physician decided that they should be considered for the study. This study indicated that patient selection may result in different outcomes between participants and non-participants, specifically, older and more severely ill patients were less likely to be entered into trials, possibly causing better outcomes to be observed for trial patients. Evidence level 3

A systematic review of 14 studies was identified that looked at whether participation in RCTs is beneficial or harmful for patients.¹³⁸ The review included cancer treatment studies but was not exclusively limited to them. The study considered different possible sources of effect and bias. Eight of the studies included in the review showed a statistically significant positive effect from trial participation, and six did not. No studies showed a negative outcome. The review concluded that a positive effect was more likely when a trial compared a known effective treatment with a new treatment. The review also concluded that it is not possible to separate protocol effect from possible bias due to clinician selection.¹³⁸ Evidence level 2++

Clinical trials should have appropriate inclusion criteria and should incorporate recognised standard treatment.