Background and aim: Patient decision aids for oncological treatment options, provide information on the effect on recurrence rates and/or survival benefit, and on side-effects and/or burden of different treatment options. However, often uncertainty exists around the probability estimates for recurrence/survival and side-effects which is too relevant to be ignored. Evidence is lacking on the best way to communicate these uncertainties. The aim of this study is to develop a method to incorporate uncertainties in a patient decision aid for breast cancer patients to support their decision on radiotherapy. Methods: Firstly, qualitative interviews were held with patients and health care professionals. Secondly, in the development phase, thinking aloud sessions were organized with four patients and 12 health care professionals, individual and group-wise. Results: Consensus was reached on a pictograph illustrating the whole range of uncertainty for local recurrence risks, in combination with textual explanation that a more exact personalized risk would be given by their own physician. The pictograph consisted of 100 female icons in a 10 x 10 array. Icons with a stepwise gradient color indicated the uncertainty margin. The prevalence and severity of possible sideeffects were explained using verbal labels. Conclusions: We developed a novel way of visualizing uncertainties in recurrence rates in a patient decision aid. The effect of this way of communicating risk uncertainty is currently being tested in the BRASA study (NCT03375801).

Background and aim There is increased attention for shared decision making (SDM) when deciding on radiotherapy for selected patients with Stage 0–2 breast cancer. This study aimed to explore patients' and health care professionals’ experiences, decisional attributes and needs as input for the development of a patient decision aid to facilitate SDM. Methods Qualitative semi-structured interviews were held with fifteen breast cancer patients, being confronted with a radiotherapy decision one month to eight years earlier. Another fifteen interviews were held with professionals specialized in breast cancer care. Interviews were transcribed verbatim and independently coded by two researchers, who agreed upon relevant issues. Results Most patients made their decision by weighing the advantages of radiotherapy, i.e. comparing the decrease in recurrence risk with and without radiotherapy, and disadvantages, i.e. possible side effects. Patients and professionals agreed that recurrence risks should be communicated, but not on how to deal with uncertainty. There was wide variation in which, and how, side effects were explained by professionals. The most common side effects mentioned by both patients and professionals were skin toxicity, fatigue and breast deformity. Conclusion Patients and professionals appeared to agree on what type of attributes should be communicated during SDM on radiotherapy, but how this should be done is up for discussion. To ensure the patient's voice these attributes and needs need to be incorporated in the risk communication and value elicitation part of the patient decision aid. The format in which the attributes are communicated should be critically evaluated.