title: A practical approach for eliciting expert prior beliefs about cancer survival in phase III randomized trial.
abstract: OBJECTIVE
  To propose and compare practical approaches that allow eliciting and using expert opinions about the benefit effect on a censored endpoint, such as event-free survival (EFS), used in the planning of a clinical trial based on Bayesian methodology.
  
  
  METHODS
  Individual interviews of 37 experts. Bayesian normal models on the log hazard ratio (HR) of EFS were implemented. We illustrate our approach by using a trial of autologous stem cell transplantation (ASCT) vs. chemotherapy (CT) in chronic lymphocytic leukemia (CLL). We elicited experts' prior beliefs about the difference in 3-year EFS between the two treatment arms, either roughly or throughout weights over the difference scale. Subsequently, a Bayesian synthesis of the information reported in the trial protocol with that in the experts' prior was performed, using: (1) the postulated treatment effect based on null (skeptical) and alternative (enthusiastic) hypotheses with shared standard error; and (2) the expected difference derived from experts' distributions.
  
  
  RESULTS
  As compared with the priors based on the trial protocol data, expert priors agreed with some average from enthusiastic and skeptical information, with close standard errors.
  
  
  CONCLUSIONS
  This case study illustrates a rational approach to construct an expert-based prior. It should be considered as part of the design of future Bayesian trials.
authors.affiliation: INSERM 9504, Centre d'Investigations Cliniques, Hôpital Saint Louis, Assistance Publique-Hôpitaux de Paris, Université Paris 7, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Hiance
authors.forename: Sylvie
authors.initials: S
authors.lastname: Chevret
authors.forename: Vincent
authors.initials: V
authors.lastname: Lévy
mesh_terms: D000970:Antineoplastic Agents / Q000627:therapeutic use; D001291:Attitude of Health Personnel; D001499:Bayes Theorem; D017326:Clinical Trials, Phase III as Topic; D005260:Female; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000401:mortality* / Q000628:therapy; D008297:Male; D016032:Randomized Controlled Trials as Topic; D033581:Stem Cell Transplantation; D011795:Surveys and Questionnaires
chemical_list: D000970:Antineoplastic Agents