UK survey indicates highly variable views on overdetection in cancer screening

Researchers at the University of Oxford (UK) have discovered that people have variable views on how much overdetection is acceptable in cancer screening. The study, published last week in The BMJ, recommends that invitations for screening include clear information on the likelihood and consequences of overdetection to allow individuals to make an informed decision. The researchers performed an online survey of 1000 individuals aged 18 years or over living in the UK. The survey contained questions on breast cancer screening for women, prostate cancer screening for men and bowel cancer screening for both men and women.  Respondents were presented with the number of absolute cases per year, and a description of treatment options and associated adverse events for each cancer type. Two different screening scenarios were then presented: one that indicated a 10% reduction in cancer-specific mortality and another that indicated a 50% reduction. Respondents were asked about the maximum number of cases of overdetection and overtreatment they were willing to accept in relation to the given benefit in each scenario. Respondents could select a number between zero (the minimum) and 1000 (entire population as maximum). The results demonstrated wide variability between respondents in the level of overdetection they would find acceptable. Lead author Ann Van den Bruel from the University of Oxford explained: “We found that people have highly variable views…with up to 7% indicating they would accept no overdetection at all and up to 14% who would accept overdetection in the entire population. Across the different cancer types, people would accept a median of 113–150 people to be overdetected to avoid one person dying of cancer as a result of screening.” The study also showed that willingness to accept overdetection for bowel cancer screening was much lower than for breast cancer screening in women and prostate cancer screening in men. Van den Bruel commented “People accepted more overdetection when they perceived a higher benefit from cancer screening, so from a 10% mortality reduction to 50% mortality reduction, median acceptability increased significantly, with a maximum of 313 cases per 1000 people screened for breast cancer.” Previously, little had been known about how much overdetection people would find acceptable for cancer screening, and whether acceptability is dependent on the level of benefit and perceived harms. Van den Bruel concluded “…personal preference is influenced by age, education level and whether people have other illnesses. To allow people to make an informed choice that is aligned with their personal values, we as a research community should get better at measuring not only the benefits but also the harms associated with cancer screening, and properly convey that information when people are invited.” Sources: Van den Bruel A, Jones C, Yang Y, Oke J,Hewitson P. People’s willingness to accept overdetection in cancer screening: population survey. The BMJ,doi: http://dx.doi.org/10.1136/bmj.h980 (2015) (Epub ahead of print); The BMJ press release