Old drug, new promise: How aspirin is emerging as a cancer fighter

One of the world's oldest medicines may have a powerful new purpose. 

A growing body of clinical evidence suggests that aspirin, the common painkiller with roots stretching back 4,000 years, can significantly reduce the risk of certain cancers forming and spreading, and researchers are finally beginning to understand why, reports the BBC.

The drug's cancer-fighting potential first drew serious attention in 2010, when Oxford Professor Peter Rothwell re-analysed data from cardiovascular trials and found that aspirin appeared to reduce both the incidence and spread of cancer. 

Since then, a series of trials has strengthened that case considerably.

Among the most compelling is a landmark study led by John Burn, a professor of clinical genetics at Newcastle University, involving patients with Lynch Syndrome, a genetic condition that raises the lifetime risk of bowel cancer to between 10% and 80%. 

In a randomised controlled trial of 861 patients followed over a decade, those who took a 600mg daily dose of aspirin for at least two years effectively halved their risk of colorectal cancer. 

A follow-up trial, currently under peer review, suggests an even lower dose of 75-100mg may be equally effective.

A separate Swedish study published in September 2025 added further weight to the evidence. 

Researchers at the Karolinska Institute tracked nearly 3,000 bowel cancer patients and found that those taking 160mg of aspirin daily had less than half the risk of cancer recurrence compared to those on a placebo. 

The results prompted Sweden to begin screening bowel cancer patients for specific tumour mutations from January 2026, offering low-dose aspirin to those who test positive.

In the United Kingdom, guidelines were updated as early as 2020 to recommend that people with Lynch Syndrome begin taking aspirin from around age 20.

A larger trial is now underway in the UK, Ireland and India, involving 11,000 participants who have had colorectal, breast, gastroesophageal or prostate cancer. 

Led by University College London's Ruth Langley, the study is testing daily doses of 100mg and 300mg, with results expected next year.

Researchers are also making inroads into understanding the mechanism behind aspirin's effect. 

One pathway involves Cox-2, an enzyme that aspirin inhibits, which normally helps produce compounds that can trigger uncontrolled cell growth. 

Another, identified by Cambridge immunologist Rahul Roychoudhuri, involves aspirin's ability to block a clotting factor that suppresses the immune system's capacity to detect and destroy cancer cells, effectively making tumours more visible to the body's own defences.

Despite the promising findings, experts caution against unsupervised use. 

Aspirin carries risks including internal bleeding, stomach ulcers and, in rare cases, brain haemorrhage. 

Most researchers stress that the drug should be taken only on medical advice, particularly for high-risk groups.

"Always speak to a doctor or other healthcare professional before starting aspirin," says Langley.

Disclaimer: All content in this article is provided for general information only and should not be treated as a substitute for the medical advice of your own doctor or any other healthcare professional.