Low public awareness of concept of ‘overdiagnosis’

In collaboration with the Press Association

People’s awareness of the idea of ‘overdiagnosis’ in cancer screening is low, and they have varying opinions of how much is acceptable, according to a new study published in The BMJ.

"It’s important that people have clear, balanced information on the benefits and harms of cancer screening" - Dr Claire Knight, Cancer Research UK

Overdiagnosis, or overdetection, of the disease is when cancers are picked up that would never have gone on to cause any harm in a person’s lifetime. 

Researchers from the University of Oxford’s Nuffield Department of Primary Care Health Sciences carried out a survey of 1,000 people in the UK to examine their views on overdetection. 

While only one in three (29 per cent) people had heard of overdetection before the study began, results indicated that people were more accepting of it when the potential benefit perceived from screening was higher. 

“How much overdetection people are willing to accept depends on the benefit that screening produces, and the cancer-specific harms of overdetection,” said lead author Dr Ann Van den Bruel. 

She added that it can also depend on personal preference, which can be influenced by age, education level and whether or not they have other illnesses.

The researchers looked at three hypothetical cancer screening scenarios: breast (for women), prostate (for men) and bowel (for men and women). 

Online respondents were given the total number of annual cases in the UK and a description of the treatment - including any adverse effects - for each type of cancer. 

They were also presented with two different screening scenarios: one indicated a 10 per cent reduction in cancer-specific deaths and the second, a 50 per cent reduction.

On average, people accepted between 113 to 150 people being overdetected per 1000 people screened. But up to seven per cent of those polled wouldn’t accept any overdetection, while as many as 14 per cent would accept overdetection of the entire screened population.

The study also found that people were less accepting of overdetection for bowel cancer screening than for breast cancer screening or prostate cancer screening. But this could be because a risk of mortality from surgery of one in 20 was included in the description of bowel cancer treatment.

Dr Claire Knight, health information manager at Cancer Research UK, said the study highlighted that overdetection was still something that only a minority of the public have heard of – and something that information on cancer screening should take into account.

“This interesting study also shows that the levels of overdiagnosis that people are willing to accept through cancer screening varies considerably,” she said. 

“So it’s important that people have clear, balanced information on the benefits and harms of cancer screening, so that they can make an individual, informed choice about whether they would like to be screened.”

In the UK there are currently national screening programmes for bowel, breast and cervical cancer.


  • Van den Bruel, A., et al. (2015). People's willingness to accept overdetection in cancer screening: population survey BMJ, 350 (mar03 23) DOI: 10.1136/bmj.h980