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Aspirin's unexpected role in cancer prevention
A 4,000-year-old painkiller, commonly used to treat inflammation and pain, is now being recognized for its potential to prevent certain cancers from forming and spreading, according to recent clinical trials. These findings are already influencing health policies in several countries.
A personal journey to prevention
Nick James, a 45-year-old British furniture maker, decided to take action after witnessing his mother's death from cancer and his brother's diagnosis of bowel cancer. Genetic testing revealed James carried a faulty gene responsible for Lynch Syndrome, a condition that dramatically increases the risk of developing colorectal cancer. Approximately 80% of individuals with Lynch Syndrome develop bowel cancer in their lifetime.
James became the first participant in a groundbreaking clinical trial led by Professor John Burn at Newcastle University. The trial aimed to determine whether a daily dose of aspirin could protect individuals with Lynch Syndrome from developing cancer. A decade later, James remains cancer-free.
"He's been on aspirin now with us for 10 years without any cancer so far," says Burn.
John Burn, Professor of Clinical Genetics, Newcastle University
From ancient remedy to modern medicine
The origins of aspirin trace back to ancient civilizations. Archaeologists discovered 4,400-year-old clay tablets in Mesopotamia (modern-day Iraq) detailing medicinal recipes, including a substance derived from willow trees. This substance contained salicin, a compound the body converts into salicylic acid, a precursor to modern aspirin. Ancient Egyptians, Greeks, and Romans also used willow-based remedies for pain relief.
The modern study of aspirin began in 1763 when English cleric Edward Stone documented the fever-reducing properties of willow bark. By the late 19th century, scientists synthesized acetylsalicylic acid, a less irritating form of salicylic acid, which Bayer later marketed as aspirin.
Scientific breakthroughs and policy changes
Early research in the 1970s hinted at aspirin's potential to prevent cancer metastasis in mice. However, it wasn't until 2010 that Professor Peter Rothwell of the University of Oxford re-examined data on aspirin's cardiovascular benefits and found evidence suggesting the drug could also reduce cancer incidence and spread. This reignited interest in aspirin's anti-cancer properties.
In 2020, Burn's team published results from a randomized controlled trial involving 861 Lynch Syndrome patients. Those who took a daily 600mg dose of aspirin for at least two years halved their risk of developing colorectal cancer. A follow-up trial, currently under peer review, suggests that a lower dose (75-100mg) may be equally effective.
These findings prompted the UK to update its medical guidelines in 2020, recommending that individuals with Lynch Syndrome start taking aspirin around age 20, or 35 for less severe cases, under medical supervision.
Expanding the scope of aspirin's benefits
Professor Anna Martling of Sweden's Karolinska Institute investigated aspirin's effects on patients already diagnosed with colorectal cancer. Her team focused on individuals with specific mutations in their bowel or rectal tumors, which affect about 40% of colorectal cancer patients. In a three-year trial involving 2,980 patients, those who took 160mg of aspirin daily after surgery had less than half the risk of cancer recurrence compared to the placebo group.
Sweden quickly adopted these findings into clinical practice. Since January 2026, bowel cancer patients in the country are screened for these mutations and offered low-dose aspirin if they test positive.
"That's a large group of the patients," Martling notes, emphasizing the significance of the results.
Unraveling the science behind aspirin's effects
The exact mechanism by which aspirin prevents cancer remains unclear, but researchers have identified several potential pathways. Martling's work suggests aspirin inhibits the enzyme Cox-2, which produces prostaglandins-compounds that can promote uncontrolled cell growth.
Recent research by Professor Rahul Roychoudhuri at the University of Cambridge proposes another mechanism. His team found that aspirin may inhibit thromboxane A2, a clotting factor that also activates a gene suppressing the immune system's ability to detect and kill metastatic cancer cells. While this research was conducted on mice, Langley's team found elevated thromboxane levels in humans with colorectal and gastroesophageal cancers, even months after successful treatment.
Future directions and cautionary notes
Professor Ruth Langley is leading a large-scale trial involving 11,000 participants across the UK, Ireland, and India to explore aspirin's effects on colorectal, breast, gastroesophageal, and prostate cancers. Results are expected next year.
While the potential benefits of aspirin are promising, experts caution against widespread use without medical supervision. Aspirin can cause side effects such as indigestion, internal bleeding, stomach ulcers, and brain hemorrhages. Martling emphasizes the importance of targeted use: "It's one thing to give aspirin to a cancer population but it's a totally different thing to offer the healthy population something that might harm them as well."
For individuals with Lynch Syndrome or a history of bowel cancer, consulting a healthcare professional about low-dose aspirin may be beneficial. As research continues, the future of aspirin in cancer prevention remains an evolving story.
