Understanding Breast Cancer Screening Overdiagnosis Alters Patient Participation

Understanding the risk of overdiagnosis influences women’s intent to undergo breast cancer screening

medwireNews: A UK survey has raised concerns about patient understanding of the risk of overdiagnosis that may occur with breast cancer screening and the impact that lack of comprehension has on their intent to undergo mammography.

For the study published in the British Journal of Cancer, 2272 women were asked about their intention to undergo screening mammography before and after they were given one of three different leaflets explaining the benefits and harms of screening, including the potential for overdiagnosis.

This included 954 women aged 43 to 70 years old who were eligible for screening in the UK and 1318 women aged 25 to 46 years who were not yet old enough for the programme.

Before being given information on overdiagnosis, 53% of participants said they were already aware of the risk and 91% of patients still said that they intended to undergo screening.

After reading the information, 90% of women stated they would probably or definitely attend screening, with 89% having no change in their intention, 4% more likely to attend and 7% less likely to attend, report Jo Waller, from University College London in the UK, and co-investigators.

At this time, 64.4% of women showed subjective understanding of overdiagnosis and 56.7% had objective understanding, defined as knowing that women who have screening mammograms are more likely to be diagnosed with breast cancer.

In all, 8.7% of patients who were given information on overdiagnosis as a ratio of one life saved to three overdiagnosis said they did not intend to undergo screening.

This compared with 5.1% of patients whose information was presented as the total numbers of lives saved and overdiagnosis made in the UK every year (1300 vs 4000) and 6.1% of patients who were given the number of lives saved and overdiagnosis per 200 women screened over 20 years (one vs three).

Women were also less likely to intend to attend screening if they were not yet eligible for the screening programme, were not previously aware of the risk of overdiagnosis and if they expressed uncertainty about how well they understood the content of a leaflet.

“The relatively poor comprehension combined with little impact on intentions suggests that brief written materials may not achieve a full appreciation of the balance of harms and benefits of breast screening, or counteract the public’s very positive attitudes towards cancer screening in general”, say Jo Waller and team.

“However”, they conclude, “the limited impact on intentions could also be interpreted in the context of the ‘better safe than sorry’ philosophy that has been observed in qualitative research.”

Reference

Waller J, Whitaker K, Winstanley K, et al. A survey study of women’s responses to information about overdiagnosis in breast cancer screening in Britain. Br J Cancer2014; Advance online publication, 28 August. doi: 10.1038/bjc.2014.482

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