Women's perception of the benefits of mammography screening: Population-based survey in four countries

Background. Screening programmes are often actively promoted to achieve high coverage, which may result in unrealistic expectations. We examined women's understanding of the likely benefits of mammography screening. Methods. Telephone survey of random samples of the female population aged ≥15 years in the US, UK, Italy, and Switzerland using three closed questions on the expected benefits of mammography screening. Results. A total of 5964 women were contacted and 4140 women (69%) participated. Misconceptions were widespread: a majority of women believed that screening prevents or reduces the risk of contracting breast cancer (68%), that screening at least halves breast cancer mortality (62%), and that 10 years of regular screening will prevent 10 or more breast cancer deaths per 1000 women (75%). In multivariate analysis higher number of correct answers was positively associated with higher educational status (odds ratio [OR] = 1.44, 95% CI: 1.25, 1.66) and negatively with having had a mammography in the last 2 years (OR = 0.86, 95% CI: 0.73, 1.01). Compared with US women (reference group) and Swiss women (OR = 0.98, 95% CI: 0.82, 1.18) respondents in Italy (OR = 0.61, 95% CI: 0.50, 0.74) and the UK (OR = 0.73, 95% CI: 0.60, 0.88) gave fewer correct answers. Conclusion. In the US and three European countries a high proportion of women over-estimated the benefits that can be expected from screening mammography. This finding raises doubts on informed consent procedures within breast cancer screening programmes.