Was The Lack of Efficacy of Trastuzumab in Low-HER2 Breast Cancer Patients Foreseeable?

Abstract

Little is known about the extent to which medical expert communities can anticipate the outcomes of clinical trials. In this study, we collected 33 expert probability distribution forecasts for an ongoing precision medicine cancer trial (NSABP-B47 or NCT01275677) on the primary outcome (incidence of disease free survival) in study and comparator arms. When trial completed and results were announced, we compared aggregate forecasts with results. The aggregated forecast underestimated IDFS for both arms of the study. However, it overestimated the IDFS advantage of the study drug. Only 44% of experts predicted the study drug would show significantly improved IDFS, and 13% predicted the study drug would show clinically meaningful IDFS advantage. Co-investigators in the trial did not show significantly greater optimism on outcome than independent experts. In conclusion, aggregated expert opinion could not predict absolute outcomes in this precision medicine trial but did predict relative outcomes with reasonable accuracy.