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 > or =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 overestimated the benefits that can be expected from screening mammography. This finding raises doubts on informed consent procedures within breast cancer screening programmes.