Purpose: Blinding patients to treatment regimen is an important component of high quality randomized clinical trials (RCTs) although concern exists over how learning about receipt of a placebo will impact participants’ views on trial participation. We sought to determine if unblinding was associated with differential changes in participants’ views of their recurrence risk and their confidence in the decision.
Methods: In Eastern Cooperative Oncology Group trial E5103, patients were randomized to receive adjuvant chemotherapy for breast cancer with either placebo or bevacizumab and treatment assignment was unblinded by 24 weeks. The Decision-Making/Quality of Life component (DM-QOL) included all patients enrolling on E5103 between 1/5- 6/8/10. Women were surveyed pretreatment and after unblinding about their perceptions of cancer recurrence risk, of risks of treatment, of feeling informed and of confidence in decision to participate in trial. Wilcoxon rank sum testing was used to examine differences.
Results: 572 patients on DM-QOL started protocol therapy; 118 on placebo, 454 on bevacizumab; the two groups were well balanced on demographic and tumor characteristics. 516 patients participated in the pretreatment survey and 514 in the unblinding survey. Pretreatment, 32% perceived a moderate or greater chance of recurrence in 5 years, 27% a moderate or greater chance of a serious problem from treatment, 99% felt at least somewhat informed, and 98% felt at least somewhat confident in study participation. Overall, median response scores did not change from baseline to unblinding, with no statistically significant differences between the groups in changes in perceptions of: recurrence risk (p=0.45); chances of a serious problem (p=0.12), or feeling informed (p=0.99). However, they differed in confidence about study participation (p=0.04): after unblinding, a higher % of placebo-treated patients had increased confidence (38% vs. 25%), and a higher % of bevacizumab-treated patients had decreased confidence (29% vs. 22%), although 44% across all arms had no change in confidence.
Conclusions: In a placebo-controlled, double-blinded RCT, unblinding did not significantly affect most participants’ views, regardless of receipt of placebo or experimental drug. However, confidence in study participation may have been affected by knowledge of receipt of bevacizumab; publicity surrounding this experimental therapy may have affected results.
See more of: The 34th Annual Meeting of the Society for Medical Decision Making