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‘Health Chatter’: Research Department of Behavioural Science and Health Blog



Can the internet help the public understand ‘overdiagnosis’ in breast cancer screening?

By rmjdapg, 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 rmjdapg, 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.

Genetic testing for all? Results of a randomised controlled trial in people of Ashkenazi Jewish descent

By Susanne F Meisel, on 5 December 2014

As I have discussed previously, genetic technology is developing at a breath-taking speed. This not only means that scientists gain better insights in the genetic contributors to disease development, but also that this comes at increasingly lower costs.

Genetic testing is not new. In fact, it has been available on the NHS  for many years. However, to be eligible for testing, certain criteria have to be met; commonly, people need to have several affected relatives to qualify for genetic testing on the NHS.

Now, with falling sequencing costs, the question of whether it would be beneficial to offer genetic testing to everyone in the population before conditions manifest becomes ever more pertinent. Proponents of the proposal argue that current approaches based on family history may miss a proportion of individuals because both individuals and healthcare providers have to recognise that there may be an increased risk of disease – this can be challenging if the family is small, or people are not very actively seeking out this information. However, other experts are more cautious and argue that large-scale genetic testing has the potential to cause more harm than good. Regardless, there are many practical, social, legal and ethical questions that have to be sorted out before genetic testing can be applied at a population level.

Currently, in the clinical setting, genetic testing is only performed after thorough genetic counselling. Genetic counselling is defined as ‘a communication process, which aims to help individuals, couples and families understand and adapt to the medical, psychological, familial and reproductive implications of the genetic contribution to specific health conditions’. Genetic counsellors meet with people one-to-one and help them to make a decision whether or not they’d like to have testing. Although research to date has found that people commonly do not react badly to their genetic test results, genetic counselling is thought to play a large role in this because people would have discussed the possibility of an unfavourable result before they got testing. In addition, because people who get genetic tests to date come from high-risk families, they may to have thought a lot about their inherited risk. Therefore, they may be better prepared to cope with an unfavourable genetic test result.

However, if lots of people in a population got genetic testing, the one-on-one model of genetic counselling would be impossible to maintain because it is far too costly and time-intensive. Some experts are concerned that providing access to genetic testing without proper genetic counselling to people who may be largely unaware of their inherited risk would result in a high rate of adverse psychological effects such as worry and anxiety.

In the first study of its kind, our researchers wanted to find out what the effects of population-based genetic testing would be. They chose to look at the effects of returning genetic test results for risk of breast-and ovarian cancer (BRCA 1/2) in the Ashkenazi Jewish population. They picked this population because people of Ashkenazi Jewish descent have a higher chance to get breast-and ovarian cancer than people from other backgrounds and the mutations causing the increased risk are well-defined. People with one of these mutations have a very high chance to get cancer (50%-80% for breast; 20%-40% for ovarian).

Specifically, the researchers wanted to investigate i) whether population-based genetic testing would be able to identify a greater proportion of mutation carriers than the current family history approach, ii) whether people would find testing acceptable, and iii) what the psychological effects (e.g. on anxiety and depression) of genetic testing would be in people which may not necessarily have a strong family history of breast-or ovarian cancer.

Potential participants were recruited in the North London Jewish community. All individuals who registered their interest received genetic counselling before they enrolled into the study, and 1,034 (691 women, 343 men) decided to take part. Participants were randomly (by chance) split into two equally sized groups: In one group, all people would get genetic testing, and in the other, only people who would qualify for genetic testing under current NICE guidelines would get testing. However, this group could access testing after the end of the study if they wanted.

Our researchers asked questions about people’s anxiety levels, depression, and general quality of life before people got genetic counselling (baseline); immediately after study enrolment; and at seven days and three months after people got their genetic test results. The researchers also asked the same questions after one, two and three years after people got their genetic test results, but the results of this bit of the study have yet to be analysed.

In the group where all people were tested for their BRCA status, 13 carriers of a faulty gene were identified vs. 9 in the group which based the testing decision on family history; an increase in detection of 56%. In the family history group, 5 more carriers were detected after the study had finished. This means that current approaches are likely to miss a significant number of people of Ashkenazi Jewish descent who carry faulty BRCA mutations. As for adverse psychological effects, there were no differences between the 2 groups at either 7 days or 3 months after people received their genetic test results. In fact, overall anxiety and uncertainty decreased quite a bit, and positive experience scores increased.

This study is the first to provide evidence that large-scale genetic testing may be beneficial and feasible; at least in certain subgroups of the population. However, in this study, all participants received one-to-one genetic counselling before they enrolled; so it is not possible to say what the effects would have been using a less tailored approach. This might be something that could be investigated in future research. Nonetheless, these results demonstrate that large-scale genetic testing may have real clinical value, and they may spark serious debate about whether the current guidelines should be amended, at least for people of Ashkenazi Jewish descent. After all, identifying BRCA carriers early may save lives.




Manchanda R, Legood R, Burnell M, McGuire A, Raikou M, Loggenberg K et al.: Cost-effectiveness of population screening for BRCA mutations in Ashkenazi Jewish women compared with family history-based testing. J Natl Cancer Inst 2015, 107.

Manchanda R, Loggenberg K, Sanderson S, Burnell M, Wardle J, Gessler S et al.: Population testing for cancer predisposing BRCA1/BRCA2 mutations in the Ashkenazi-Jewish community: A randomized controlled trial. J Natl Cancer Inst 2015, 107

Can catching cancer early ever be a bad thing?

By Susanne F 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