Improving decision making about clinical trial participation - a randomised controlled trial of a decision aid for women considering participation in the IBIS-II breast cancer prevention trial.

Background: Decision aids may improve informed consent in clinical trial recruitment, but have not been evaluated in this context. This study investigated whether decision aids (DAs) can reduce decisional difficulties among women considering participation in the International Breast Cancer Intervention Study-II (IBIS-II) trial.

Methods: The IBIS-II trial investigated breast cancer prevention with anastrazole in two cohorts: women with increased risk (Prevention), and women treated for ductal carcinoma in situ (DCIS). Australia, New Zealand and United Kingdom participants were randomised to receive a DA (DA group) or standard trial consent materials (control group). Questionnaires were completed after deciding about participation in IBIS-II (post decision) and 3 months later (follow-up).

Results: Data from 112 Prevention and 34 DCIS participants were analysed post decision (73 DA; 73 control); 95 Prevention and 24 DCIS participants were analysed at follow-up (58 DA; 61 control). There was no effect on the primary outcome of decisional conflict. The DCIS-DA group had higher knowledge post decision, and the Prevention-DA group had lower decisional regret at follow-up.

Conclusions: This was the first study to evaluate a DA in the clinical trial setting. The results suggest DAs can potentially increase knowledge and reduce decisional regret about clinical trial participation.