The risk factor – new evidence on obesity and prostate cancer

Casting an eye over our cancer prevention infographic it’s noticeable that there’s no mention of prostate cancer. That’s because, until now, researchers haven’t been able to uncover much about what causes the disease, and what people can do to reduce their risk.

Yesterday, as part of its Continuous Update Project, the World Cancer Research Fund (WCRF) published an in-depth look at the latest evidence on preventing prostate cancer, with some new and interesting conclusions that you may have seen in the media.

The organisation grades evidence based on the strength and reliability of all the research combined. Its top two categories are ‘convincing’ and ‘probable’, when the evidence is so strong that it can be talked about confidently, and even lead to recommendations for the public.

So what has it found?

Its most significant finding is that men who are overweight or obese are at greater risk of ultimately developing an aggressive form of prostate cancer.

It also found that fully grown adults’ height ‘probably’ affects risk, but because this is determined by early life and genes, men can’t do much about it (although it does give clues for more research into how the disease develops).

Several other things were actually downgraded in terms of the strength of their evidence.

For example, tomatoes are unlikely to play a role in preventing prostate cancer. Tomatoes, along with certain other foods, contain a naturally occurring chemical called lycopene, which in the previous analysis in 2007 was said to ‘probably’ reduce the risk of developing prostate cancer. But the scientists have now concluded that the latest evidence isn’t strong enough to suggest whether or not lycopene plays a role in prostate cancer development.

And the evidence linking a diet high in calcium with an increased risk of prostate cancer has also been downgraded from ‘strong’ to ‘limited.’

Tipping the balance

For us, the key finding here is about obesity. Earlier on this year we blogged about the mounting evidence behind obesity and cancer, but prostate cancer was barely mentioned, so why is this latest research now showing a strong link?

The report published today looks at the collective results of a lot of studies. This is called a ‘meta-analysis’, and groups smaller pieces of evidence together to help us see the bigger picture. Researchers found that the more excess body fat you are carrying, the greater your risk of being diagnosed with an advanced prostate cancer. By assessing the collective power of research we now have a clue as to the first risk factor related to prostate cancer that a man can control.

So what’s the catch?

WCRF has only been able to reach this conclusion in relation to more advanced forms of prostate cancer. It has defined these as prostate cancers that are more aggressive or have grown and spread.

But not all prostate cancers will develop into these more aggressive forms. And one of the major challenges in prostate cancer is finding a reliable way of distinguishing between cancers that will never cause any harm to the patient, and these more aggressive forms that can be fatal.

We know that the more aggressive forms are harder to treat, which could make these latest findings extremely important. And with these findings men can help reduce their risk of these more aggressive, potentially fatal cancers.

But the report’s conclusions could only be reached in relation to these more advanced cancers, because that is where the high-quality research has been carried out. There isn’t yet enough evidence to put the whole prostate cancer puzzle together, meaning there are still many unanswered questions, which future research can now look to answer.

For example, does being fatter just mean men are diagnosed with prostate cancers later? Or does the fat itself actually play a role in these tumours becoming more aggressive?

By analysing all these data together and uncovering these links, researchers will now be able to start asking these questions.

What does this all mean?

This new research is big news. It means that men can help to reduce their chances of developing prostate cancer – where before there was nothing they could really do, there is now a way that men can stack the odds in their favour.

As we’ve written about before, reducing your risk doesn’t guarantee you’ll never get cancer – and we certainly aren’t saying that if you have cancer, it’s your fault.

But it is now clear that we can add prostate cancer to the list of cancers that are linked to a higher body weight. Using this knowledge we can support and encourage people who are trying to make lifestyle changes.

And that is pretty big news, no matter how you look at it.

Tom Stansfeld is a health information officer at Cancer Research UK

• For more information about keeping a healthy weight and making lifestyle changes that will help reduce your risk of cancer check out cruk.org/weight

Image

Weighing scale image by Christoph, accessed via Flickr under a Creative Commons CC-BY-NC-ND 2.0 license