New analysis outlines risks and benefits of taking aspirin to reduce risk of cancer

A new analysis published today outlines the risks and benefits of taking aspirin to reduce the risk of cancer.

You'll probably have seen the media coverage today about aspirin, and whether it can help prevent cancer.

The news comes from a new scientific report by international experts (including some funded by Cancer Research UK), looking at all the available evidence about the over-the-counter drug's pros and cons.

So what are they saying? And should you or I start taking it today? Well, the drug has risks as well as benefits, so our advice is: don't take it without talking to your GP.
This graphic sums up the new data, and the unanswered questions.

So why the uncertainty?

The story so far
Today's headlines are the latest chapter in a story that's been unfolding over the last few years. We've been following it since 2008, when we wrote this in-depth explainer about the state of the evidence.

In 2009, our researchers produced a new report, discussed here, concluding that more research was still needed. Then, in 2010, a new analysis by researchers in Oxford suggested that the pros were beginning to outweigh the cons - although our experts still called for caution.

The last big announcement on the subject came in 2012, when the Oxford team published new data refining what was known about the balance of pros and cons. We discussed this extensively and, if you read one post on the subject, it's this one, as it goes into detail about how the risks and benefits change over time.

So what's new?

And so to today's news. The latest analysis, published in the Annals of Oncology, pulls together data from all available studies and clinical trials, and analyses where the balance lies more clearly than ever before.

It confirms that aspirin protects most strongly against bowel, stomach and oesophageal cancers, and also more weakly against lung, prostate and breast cancers. It suggests that the benefits start building from age 50, so there's little to gain from taking it below that age. And it finds that if 1,000 people (500 men and 500 women) aged 60 take aspirin for ten years then - compared with 1,000 people who DIDN'T take aspirin - over the next 20 years you'd see:

Pros:
Around 17 fewer deaths, including:  16 fewer deaths from cancer overall  1.4 fewer deaths from heart attacks

Cons:
Between two and three extra death from:  1.4 more lethal strokes  0.3 more serious peptic ulcers  0.65 more lethal gastric bleeds Sounds positive overall, right? Well there are a few important omissions from the analysis that begin to muddy the waters.

It's a bit more complicated than that

These risks and benefits aren't evenly spread around the population. Some are at higher risk of side effects. Some people's genetic make-up means they break down aspirin at different rates - some faster, some slower, than average. Some will have a lower risk of cancer without even taking the drug, so they won't benefit as much (though they may still experience side effects). It's an extremely complex, and still slightly murky,  picture.
So to be able to recommend aspirin to people in the full knowledge that the risks are being minimised, and the benefits maximised, doctors need to have a better idea of the following:  What age should people start, and stop, taking aspirin?  What dose should they take?  What are the factors that should rule someone out from taking aspirin, and how should we test for them?

At the moment, frustratingly, there's no clear, definitive answer to these questions. And until there are, we're discouraging people from stocking up on their own supplies of aspirin without seeking medical advice first. So if you're worried about your risk of cancer, and want to do something about it, your first port of call should always be your GP.