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

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.