title: Greater expectations in a cancer trial: absolute more than relative survival increases, community more than academic clinicians.
abstract: There is no consensus on how the difference between control and experimental outcome rates, the clinically important difference, should be estimated when designing a clinical trial. We sought to determine whether community and academic clinicians had different perceptions as to what would constitute a clinically important increase in survival, when asked to respond in absolute or relative terms, before a trial was started rather than when the results were already known. A telephone survey of 25 practicing Canadian oncologists was performed. Questions were asked as to the importance of acceptable and minimally acceptable improvements in survival for a hypothetical trial of pancreatic cancer where the baseline survival was expected to be between 2 and 8 months. Responses were sought for absolute (additional months) or relative gains (percent improvement) in survival. The mean absolute additional survival expectations corresponded to at least a doubling of baseline survival and tended to be greatest when the prognosis was poorest (p = 0.06). Relative expectations for improved survival varied with baseline survival (p < 0.001). When improvement in survival was requested in relative terms, the median expected improvement was 25%. This is highly significantly different than when survival improvements were requested in absolute terms (p < 0.0001). Median absolute survival expectations were greater for community as compared with academically affiliated physicians (p = 0.046). We found that physicians are inconsistent in their interpretation of qualitative data. What constitutes a potentially clinically important treatment effect differs whether viewed in relative or absolute terms before the performance of a trial. Expectations were greatest when the prognosis was poorest and differed between community and academic physicians.
authors: Department of Medicine, University of Western Ontario, London, Canada. dmassel@lhsc.on.ca
authors: D
authors: D
authors: Massel
authors: M
authors: M
authors: Cruickshank
mesh_terms: D000328:Adult; D002170:Canada; D002986:Clinical Trials as Topic; D015986:Confounding Factors, Epidemiologic; D005180:Faculty, Medical / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010190:Pancreatic Neoplasms / Q000401:mortality* / Q000628:therapy*; D010820:Physicians / Q000706:statistics & numerical data*; D010818:Practice Patterns, Physicians'; D011795:Surveys and Questionnaires; D016019:Survival Analysis; D016896:Treatment Outcome