Benefit and Risk of Mammography Screening – Considerations from an Epidemiological Viewpoint: Judgement and Decision Processes

Abstract

According to the authors, many women may choose to participate because they have followed the principle of multiplying the low probability of the adverse event in question (death from breast cancer) by the high magnitude, as it were, of the event (death). It is certainly true that many women would still choose to undergo mammography even if they knew that a healthy woman’s chance of avoiding death from cancer with the aid of early detection is low. Yet precisely this fact is withheld from women in the informational materials that they are generally given in the German-speaking countries. Thus, they are not in a position to make the actuarial evaluation described. The likelihood of a catastrophically adverse event, such as overdiagnosis followed by overtreatment, is likewise low but obviously should also be part of the evaluation and decision process. It has been well documented empirically that decisions depend on the nature and extent of the information provided. Presenting the effect of the intervention only in terms of relative risk creates an unrealistically positive impression (1). Patients consider themselves well-informed if they know absolute numbers and absolute risks (2). Varying presentations of identical facts – half empty versus half full – can lead patients to make different decisions. I think there can only be one conclusion: the judgement about the probabilities of benefit and harm should be left up to each individual woman on the basis of comprehensive information that does not predetermine her ultimate decision. There is no good reason to withhold understandable information from women, as has been done up to the present. Understandable information that should be communicated includes at least the following: the risk of breast cancer in the individual woman’s age group, the likelihood of avoiding death from cancer by early detection, the rates of false positive and false negative findings, and the danger of overdiagnosis leading to overtreatment (3).