We’ve talked in this blog before about how cancer screening has harms as well as benefits; the most serious of which is the potential for overdiagnosis or over-detection – that is, picking up cancers that never would have done any harm, and that would never have come to light if we hadn’t looked for them.  This is something that is far from intuitive for many people and that runs counter to long-standing messages about the importance of ‘catching cancer early’.  This BMJ blog explains some of the issues really well.

In a new study just published by our group, we found that public enthusiasm for cancer screening was very high indeed.  We carried out a survey of nearly 2,000 men and women aged 50-80 years across the UK and found that 89% of them thought that cancer screening for healthy people is ‘almost always a good idea’.  Most people believed that finding cancer early means that less treatment will be needed, and that treatment is more likely to be life-saving.  This is generally true, so it’s great to see that message has really entered the public consciousness.

More surprising was the finding that nearly half of the respondents said that they would want to be tested to see if they had the kind of slow-growing cancer that would be unlikely to cause harm in their lifetime.  Most experts in the field assume that if people understood about the risk of overdiagnosis, they would make different decisions about screening participation.  Our findings suggest that this might not be the case.

One possibility is that people don’t understand that this kind of diagnosis might lead to unnecessary surgery, chemotherapy or radiotherapy, with all the side-effects that those treatments involve.  Another possibility is that people have such an entrenched view of cancer as a killer that they find it difficult to conceive of having a tumour that might not need treatment – and would rather have it removed, even if there’s no clear health benefit to doing so (in fact, it may even harm their health).

Opinion was spilt about the value of knowing about an incurable cancer – 49% of the sample would still want to know, even if nothing could be done, but 46% would rather not know.  Perhaps people vary in how important it is for them to have time to plan for their death, and how this weighs against the benefits of enjoying life without a cancer diagnosis.

The NHS offers screening for breast, cervical and bowel cancers, but encourages people to make an informed choice about whether to take part or not.  In our sample, two thirds of women, and almost as many men judged a person who doesn’t go for screening to be ‘irresponsible’, suggesting that not everyone sees non-attendance for cancer screening as a legitimate, personal choice.

We continue to work on finding the best ways to communicate with the public about cancer screening so that everyone can understand the harms and benefits and make a choice about whether to take part.  This study has made us realise that it could be difficult to persuade people that screening is only worthwhile for certain cancers and in certain groups.

It’s great that the message about the potential benefits of early diagnosis are getting through, but now we may need more nuanced messages to help people understand the exceptions to this rule, and to acknowledge that in some cases, not being screened is a sensible decision.