We take a closer look at new research claiming that blood test based on measuring changes in zinc could detect breast cancer early.

Wednesday 10 December 2014      Research blog
Over-hyped test for breast cancer - it’s not always the journalists’ fault

Today the media have reported on new research from Oxford University claiming that a blood test based on measuring changes in zinc could detect breast cancer early.  One paper stated that the test could ‘detect cancer long before symptoms - and spell the end of the mammogram’.  Is there truth in this? We took a closer look at the research to see what’s really going on.

Zinc, breast cancer and early diagnosis

In this study the researchers wanted to find out if an analytical technique, commonly used to measure metal composition in soil, could be used to measure levels of zinc in blood from breast cancer patients.  The reasoning behind this comes from the knowledge that breast cancer tissue takes up more of the ‘light’ form of zinc, leaving behind much more ‘heavy’ zinc in the blood.  This skews the ratio of heavy to light zinc in the blood of patients and could be used as a way to detect breast cancer.

The researchers analysed ratios of zinc in the blood and tissue of 10 people – five with breast cancer and five healthy individuals – and discovered that their test was able to detect differences in the ratios of zinc in breast cancer tissue but not in the blood.

So the researchers haven't actually shown that analysing zinc in blood could form a basis of a new test for breast cancer, as claimed in the media reports.  Furthermore,  this test was done on 10 people, an extremely small number, so we have to accept that there is a good chance the test woudln't even work on a larger group.

When Cancer Research UK were asked to comment on this research they said: “The results of this research are unlikely to lead to the development of a blood test to help diagnose breast cancer. The study is small and shows no measurable difference in the levels of zinc in the blood of people with breast cancer compared to healthy individuals."

"Uncovering new ways to diagnose cancer earlier is really important to help more people survive cancer. Analysing markers in the blood could one day be part of this, but research into blood tests is still at a very early stage."

A leap of faith

Another significant problem is how this result has been interpreted in the media.  It has been stated that this test could ‘detect cancer earlier than mammograms’ and ‘could be used in future to screen all women for early signs of breast cancer’. 

This is an incredible leap of faith.  We don’t know anything about how early on in the disease these changes in zinc could be detected.  The five people analysed in this research already had breast cancer so how could that translate to early detection of the disease?  Without knowing this, it’s not sensible to say this test could be better than mammograms or become part of the screening programme.

Chinese whispers

It’s not surprising to see the media over-stating and misinterpreting research, and we always like to pin the responsibility on them.  But sometimes the media can only work with what is given to them in a press release.  By pure coincidence, Ben Goldacre published an article in the BMJ today highlighting exaggerations by academics and press offices as a key reason why research becomes misrepresented by the media. Looking at the press release for the zinc research mentioned here, it seems that this may be the true culprit in the media hype.

When reporting research to the public, everybody involved has a duty to ensure that the work is presented in a factual and sensible manner.  This isn’t just being pedantic because, as Goldacre mentions in his article, evidence exists to suggest that media reporting of research influences uptake of treatment and health services.  The direct impact of the media on public health has the potential to be extremely powerful. We need to ensure that journalists, press offices and importantly, the researchers themselves, understand the responsibility they have to the fair reporting of research.

Dr Matthew Lam is Breakthrough Breast Cancer's Senior Research Officer