‘Health Chatter’: Research Department of Behavioural Science and Health Blog
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    Can the internet help the public understand ‘overdiagnosis’ in breast cancer screening?

    By Alex Ghanouni, on 20 April 2016

    Authors: Alex Ghanouni, Cristina Renzi & Jo Waller

    In our last blog, we talked about ‘overdiagnosis’, a concept that many people are unfamiliar with – that is, when a medical test finds an illness that would never have caused any harm during a person’s lifetime.

    As a follow-up study, we were interested in how much information the UK and Australian public could find online about overdiagnosis in the specific context of breast cancer screening.

    Why breast cancer screening?

    We chose breast screening because it is a setting in which the issue of overdiagnosis has received a lot of attention in the UK in recent years: in 2011, Cancer Research UK and the Department of Health commissioned a review of studies with the aim of understanding how much overdiagnosis happens in breast screening.

    Likewise, the NHS recently made substantial changes to the information leaflets provided to women invited for breast screening, with the aim of ensuring that they would understand that overdiagnosis was one possible outcome of being tested.

    Breast screening sometimes diagnoses ‘ductal carcinoma in situ’ or ‘DCIS’, which is an abnormality that can become a symptomatic cancer over time. However, it can also be slow growing and never pose a health risk, meaning that a large proportion of overdiagnosis in breast screening is due to DCIS.

    As well as finding out what kind of information people could find about overdiagnosis on health websites, we were interested in what explanations those websites provided about DCIS, and also what kinds of statistics were used to give the public a sense of how many people are affected by overdiagnosis.

    We used a Google search for ‘breast cancer screening’ to find the most relevant health websites in the UK and Australia (such as NHS Choices and Cancer Australia). We examined in detail ten websites from the UK and eight from Australia.

    What did we find?

    Our main findings were that most UK websites included some information about overdiagnosis and also DCIS. The websites provided a range of statistics stating, for example, that every year around 4,000 women in the UK are overdiagnosed and overtreated following screening and that around 3 in 200 women screened would be overdiagnosed and overtreated (considering women aged between 50 and 70 years undergoing screening every three years).

    Such information was available less often on Australian websites, although the kind of information was similar when it was present (and several websites linked to more detailed websites instead of hosting the information themselves).

    Why is this important?

    One reason for doing this research was that a similar study had been carried out more than ten years ago in 2000, showing that overdiagnosis and DCIS were rarely described. We thought that things might have changed in the meantime as more and more people use the internet to understand health issues.

    In fact, we found that although not every piece of information on overdiagnosis and DCIS is available on every website, it is more available than it was in the past. In time, this might lead to a greater level of public awareness about the issue.

    What does the UK public understand by the term ‘overdiagnosis’?

    By Alex Ghanouni, on 14 April 2016

    Authors: Alex Ghanouni, Cristina Renzi & Jo Waller

    In recent years, doctors and academics have become more and more interested in a problem referred to as ‘overdiagnosis’. There are several ways that overdiagnosis can be defined.

    One particularly useful way is to think of it as the diagnosis of a disease that would never have caused a person symptoms or led to their death, whether or not it had been found through a medical test. In other words, even if a person had not had the test, the disease would never have caused them any harm.

    Catching it early

    It may not be obvious how this can happen. As an example, imagine a woman going for breast screening, which tries to find cancer at an early stage, before it starts causing symptoms.

    The thinking behind this type of test is that if the disease is found early, it will be easier to treat and there is a higher chance of curing it. Most people are familiar with this idea that ‘catching it early’ is a good thing.

    So, suppose a woman who has no symptoms goes for screening and the test finds cancer: she would usually go on to have treatment (e.g. surgery).

    However, although she has no way of knowing for sure, it is possible that the cancer was growing so slowly that she would have lived into old age and died of something unrelated, without ever knowing about the cancer, had she not gone for screening.

    The cancer is real but the diagnosis does not benefit the woman at all; it results in treatment that she did not need (‘overtreatment’). In fact, if she had not had the screening test, she would have avoided all the problems that come with a cancer diagnosis and treatment.

    What research has found

    If you find the idea of overdiagnosis counter-intuitive, you are not alone. Several studies have tried to gauge public opinion on the issue and found that this is a fairly typical view, partly because the notion that some illnesses (like cancer) might never cause symptoms or death is one that does not receive much attention and is often at odds with our personal experiences.

    Results from an Australian study in 2015 found that awareness of ‘overdiagnosis’ is low – in a study of 500 adults who were asked what they thought it meant, only four out of ten people gave a description of the term that was considered approximately correct and these descriptions were often inaccurate to varying degrees.

    For example, people often thought in terms of a ‘false positive’ diagnosis (diagnosing someone with one illness when really they do not have that illness at all), or giving a person ‘too many’ diagnoses.
    Is this the same in the UK?

    We wanted to find out whether this was also true in the UK. We asked a group of 390 adults whether they had come across the term ‘overdiagnosis’ before and asked them to describe what they thought it meant in their own words, as part of an online survey.

    We found that only a minority (three out of ten people) had encountered the term and almost no-one (10 people out of all 390) described it in a way that we thought closely resembled the concept described above.

    It was not always clear how best to summarize people’s descriptions but we found that people often stated that they had no knowledge or had similar conceptions to the Australian survey such as ‘false positives’ and ‘too many’ diagnoses.

    Some descriptions were somewhat closer to the concept of overdiagnosis such as an ‘overly negative or complicated’ diagnosis (e.g. where the severity of an illness is overstated) but there were also some descriptions that we found more surprising such as being overly health-conscious (e.g. worrying too much about health issues).

    Room for improvement

    Many people who work in public health and healthcare believe that people should be aware of the possibility of overdiagnosis, particularly since they will eventually be offered screening tests in which there is this risk.

    In this respect, our findings show that there is substantial room for improvement in how we inform the public about overdiagnosis. In part, this may be due to the term itself not having an intuitive meaning, in which case other terms might be more helpful (for example the term ‘unnecessary detection’).

    This could be tested in future studies. Our findings also motivated us to find out the extent to which trusted information sources (such as websites run by the NHS and leading health charities) are already providing information on overdiagnosis.

    We would like to share the findings from this study in a follow-up blog post. We will be posting this here soon.

    This was originally posted on the BioMed Central blog network.

    Public enthusiasm for cancer screening

    By Jo Waller, on 10 February 2015

    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.

    Can catching cancer early ever be a bad thing?

    By Susanne Meisel, on 31 August 2014

    The chance of surviving cancer is usually much better if it is found early; ideally before a person has any symptoms. One way to achieve earlier detection of cancer is by screening.

    Breast cancer screening is one of the three NHS cancer screening programmes and is currently offered to all women aged 50 to 70 in the UK. This is done using mammography, which can detect cancers that are too small to see or feel.

    Breast cancer screening is a form of secondary cancer prevention because it does not prevent breast cancer from happening in the first place; it only helps to find it earlier. Primary breast cancer prevention, on the other hand, is everything a person does to try and prevent breast cancer from ever developing; for example by not smoking, keeping alcohol within sensible limits and keeping a healthy weight. Although doing those things does not guarantee that a person will never get breast cancer, there is good evidence that it will reduce the chance.

    However, any type of cancer screening not only has benefits, but also the potential to cause harm. An independent expert panel was asked not long ago to weigh up the benefits and harms of breast screening. They concluded that on balance, breast screening has more benefits than harms. Therefore, it is still recommended.

    One particular risk of harm that the breast screening panel identified was overdetection (sometimes known as overdiagnosis). Overdetection happens when a cancer is picked up by a mammogram which would have never caused a problem during a woman’s lifetime – either because it was slow-growing, or because she would have died of something else before the cancer became a problem. However, because it is currently impossible to tell whether a cancer is ‘dangerous’ and fast-growing, or won’t cause further problems because it’s growing only very slowly, all cancers are treated as ‘dangerous’. This means that some women will have treatment that is very invasive and distressing (for example breast surgery or chemotherapy) when actually the cancer would not have caused them any harm. Currently, it is estimated that for every life saved by screening, three cancers are detected that would have not caused any problems.

    Whether or not to attend breast cancer screening is a personal choice .
    However, for women to make an informed choice about breast screening, they need to know about all the benefits and harms, including the risk of overdetection.

    Our researchers carried out a survey with 2,272 women from the general population to find out whether women knew about overdetection, and whether getting some information on it would influence their decision to go for breast screening. Therefore, they asked women about screening intentions, before and after giving them information on overdetection. Women were told about the problem of treating cancers that never would have caused harm, and that for every woman who has her life saved by breast screening, three will have treatment for a cancer that would never have become life-threatening. The researchers thought that younger women (<47) who were not yet eligible for screening would have lower intentions to go for screening after hearing some information about overdetection than women who were already eligible for breast screening, because the latter may already have made up their minds.

    The results showed that about half of the women (53%) were already aware of overdetection, with greater awareness among women who were already eligible for screening. However, even after getting some information on overdetection, only about two thirds of the sample (64%) felt that they understood what the concept meant, and a similar number (57%) understood that women who go for breast screening are more likely to be diagnosed with breast cancer than women who don’t. Interestingly, only a small number of women (7%) showed a decrease in screening intentions after receiving information on overdetection. As predicted by the researchers, a greater number of these women were not yet eligible for breast screening.

    These findings suggest that the concept of overdetection may be difficult to understand for some women, and that brief information may not be enough to help them make an informed choice. However, one limitation of this study was that women had very little time to take in the information that was given to them. Perhaps understanding would have improved if women had had more time to process what it meant. Alternatively, it is possible that women took a ‘better safe than sorry’ approach to overdetection, which has been suggested by findings from some focus groups that our researchers did with 40 women.

    Future work will help to understand how best to communicate the benefits and harms about cancer screening to different groups of people, so that they can make a truly informed choice about whether or not to participate.



    Waller, J et al. A survey study of women’s responses to information about overdiagnosis in breast cancer screening in Britain (2014) British Journal of Cancer. doi: 10.1038/bjc.2014.482

    Waller J, Douglas E,Whitaker KL, et al Women’s responses to information about overdiagnosis in the UK breast cancer screening programme:a qualitative study. BMJOpen 2013;3