Imagine if a cheap, accessible and relatively safe pill could prevent cancer in those who have never had it and stop it from returning among those in remission. The idea that aspirin is such a “wonder drug” is the subject of intense research, but the picture is muddled.
The notion that aspirin could have anti-cancer properties dates back decades. In 1988, researchers in Australia linked the painkiller to a , or bowel, cancer. of these observational studies have since tried to untangle the relationship between aspirin and different types of cancer.
Much of this focus has been on colorectal cancer. In fact, daily aspirin is by the National Institute for Health and Care Excellence (NICE), a UK medical guidelines body, for people with Lynch syndrome, a genetic condition that of the condition. Aspirin may be effective for these people because it suppresses or destroys lesions in the gut that could turn cancerous.
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But for people without Lynch syndrome, the situation is much less clear-cut. While some studies suggest of colorectal cancer, found that it was no better than a placebo at helping people who had already been treated for colorectal cancer to live longer after completing treatment.
even linked daily aspirin to a higher rate of cancer-related deaths among older people. This was particularly true for gastrointestinal cancers, including colorectal ones.
But at Harvard University wasn’t convinced that this trial, called ASPREE, provided all the answers on aspirin’s cancer-protecting potential. “ASPREE was a very narrow population,” he says. “Participants were over the age of 70 years old and the follow-up was short, less than 5 years.”
So Chan decided to investigate further. Focusing on colorectal cancer, he and his team looked at 30 years of data on more than 100,000 individuals in the US, who self-reported whether they regularly took aspirin. The results suggest that at least two tablets a week could prevent colorectal cancer – but mainly among those with the unhealthiest lifestyles. Those with healthier habits, such as eating well and not smoking, seemed to benefit to a much lesser extent.
Off the back of these findings, Chan believes the key is to personalise aspirin prescription guidance for people who stand to benefit the most, for instance, those who don’t follow to reduce their colorectal cancer risk, such as by exercising regularly.
“I am hopeful that in the future we will be able to define better the subsets of the population that are more likely to benefit from aspirin and the subgroups who have any potential harms,” he says.
Chan has no plans to test this in a randomised controlled trial, which would help to determine whether aspirin’s side effects, such as stomach ulcers and bleeding, would be tolerable for such use.
“It’s very clear the risk of bleeds and fatality associated with the bleeding rises rapidly from [age] 70 onwards,” says at Queen Mary University of London. He wonders if it might be best to consider aspirin’s use for this purpose starting from about age 50, for five to 10 years.
Complicating matters further, aspirin’s effects seem to vary by cancer type. For example, a study of more than 1 million people over 20 years suggests that long-term aspirin use may of certain cancers, such as those of the colon, rectum and stomach, but raise the odds for lung and bladder cancers. Meanwhile, a from April 2024 found that among people in remission for breast cancer, daily aspirin did not prevent recurrence or survival over a placebo.
Yet supports Chan’s stance that personalisation may be key. at the Karolinska Institute in Sweden and her colleagues found that colorectal cancer is about half as likely to recur if aspirin is given to people with specific genetic mutations after they have surgery to treat the condition. “This is quite a stunning benefit from what is just a cheap, easily available drug,” says at the National Cancer Centre Singapore. “Certainly larger studies will need to further confirm this encouraging result.”
These mutations are in around of colorectal cancers and involve a signalling pathway, called PI3K, that may , progression, spread and drug resistance – a pathway that aspirin may block.
A recent in mice also suggests that it may be worth not throwing in the towel quite yet. żěè¶ĚĘÓƵs at the University of Cambridge found that aspirin reduces the production of a lipid called thromboxane A2, which hampers the ability of immune cells called T-cells to recognise and kill cancer cells that are spreading in the body, supporting the idea that the drug has protective potential.
“I think what all this shows is that the jury is still out on whether aspirin can reduce the spread of cancer in people,” says team member . In the future, as more research uncovers how aspirin may affect cancer risk, we could focus our attention on figuring out who may benefit most, he says.
