Abstract
BACKGROUND: Adherence to adjuvant endocrine therapy (AET) is low in women with breast cancer. Negative beliefs about the necessity of AET and high concerns are barriers to adherence. PURPOSE: To use the multiphase optimization strategy to optimize the content of an information leaflet intervention, to change AET beliefs. METHODS: We conducted an online screening experiment using a 25 factorial design to optimize the leaflet. The leaflet had five components, each with two levels: (i) diagrams about AET mechanisms (on/off); (ii) infographics displaying AET benefits (enhanced/basic); (iii) AET side effects (enhanced/basic); (iv) answers to AET concerns (on/off); (v) breast cancer survivor (patient) input: quotes and photographs (on/off). Healthy adult women (n = 1,604), recruited via a market research company, were randomized to 1 of 32 experimental conditions, which determined the levels of components received. Participants completed the Beliefs about Medicines Questionnaire before and after viewing the leaflet. RESULTS: There was a significant main effect of patient input on beliefs about medication (β = 0.063, p < .001). There was one significant synergistic two-way interaction between diagrams and benefits (β = 0.047, p = .006), and one antagonistic two-way interaction between diagrams and side effects (β = -0.029, p = .093). There was a synergistic three-way interaction between diagrams, concerns, and patient input (β = 0.029, p = .085), and an antagonistic four-way interaction between diagrams, benefits, side effects, and concerns (β = -0.038, p = .024). In a stepped approach, we screened in four components and screened out the side effects component. CONCLUSIONS: The optimized leaflet did not contain enhanced AET side effect information. Factorial experiments are efficient and effective for refining the content of information leaflet interventions.