Background: Supporting women to make well-informed decisions about breast-cancer screening requires effective communication about screening outcomes including overdetection or overdiagnosis (diagnosis and treatment of cancers that would never become clinically evident).
Objectives: We investigated the effects of providing information about overdetection in a decision aid for women aged around 50 considering breast screening. Immediate post-intervention results (reported previously) showed that the intervention increased knowledge and informed choice, made screening attitudes less positive and reduced intentions to screen. We now present 2-year follow-up data.
Methods: We did a community-based RCT in Australia with a random cohort of women aged 48-50 who had not undergone mammography in the past 2 years and had no personal or strong family history of breast cancer. We randomised 879 women to receive the intervention decision aid (evidence-based information on overdetection, breast cancer mortality reduction, and false positives) or a control decision aid (identical but without overdetection information). Two years later we assessed women’s knowledge, attitudes and future screening intentions, plus screening uptake.
Results: 712 women (81% of those randomised) completed 2-year follow-up. Compared with controls, more women in the intervention group retained adequate conceptual knowledge (34% vs. 20%, p<.01). Groups were similar in the proportions of women who expressed positive attitudes to screening (81% vs. 82%, p=.66), underwent mammography during the 2-year follow-up period (50% vs. 51%, p=.75) and reported intending to screen within the next 2-3 years (82% vs. 85%, p=.25).
Conclusions: A brief decision aid led to long-lasting improvement in women’s understanding of potential consequences of breast screening, including overdetection. Few previous decision-aid trials have demonstrated an impact persisting over such a long timeframe. Although screening intentions were lower in the intervention group than among controls immediately post-intervention, after 2 years we have not observed an effect on mammography uptake nor future breast-screening intentions.