Aspirin's Role in Bowel Cancer Prevention Questioned by New Study
Recent research has determined that aspirin does not offer a rapid or assured method for preventing bowel cancer, while it poses immediate dangers of severe bleeding associated with a rare form of stroke. The findings, published in the Cochrane Database of Systematic Reviews, rely on evidence from 10 randomised clinical trials.
Analysis of Long-Term Effects and Immediate Risks
Researchers from West China Hospital of Sichuan University examined data from 124,837 participants to evaluate whether aspirin could avert bowel cancer or precancerous polyps in individuals at average risk. Their review indicates that aspirin is unlikely to diminish the risk of bowel cancer within the initial five to 15 years of use. However, some studies noted possible protective effects after more than 10 to 15 years of follow-up.
These potential long-term advantages stem from observational follow-up phases of trials, where participants might have discontinued aspirin, initiated it independently, or commenced other treatments, rendering the findings susceptible to bias. Lead author Dr Zhaolun Cai stated: 'While the idea of aspirin preventing bowel cancer in the long run is intriguing, our analysis shows that this benefit is not guaranteed and comes with immediate risks.'
Bleeding Hazards and Vulnerable Groups
The findings also provide clear evidence that daily aspirin use elevates the risk of serious extracranial haemorrhage—bleeding occurring between the skull and the scalp—and can increase the likelihood of haemorrhagic stroke, which happens when a blood vessel ruptures in the brain and leaks its contents into the organ.
Although higher doses pose the greatest risk, low-dose ('baby') aspirin also raises bleeding risk. Older adults and those with a history of ulcers or bleeding disorders may be especially vulnerable. The authors caution that any potential long-term benefit of aspirin must be balanced against the immediate and well-established risk of bleeding.
Expert Warnings and Precision Prevention
Dr Bo Zhang, senior author, expressed concern: 'My biggest worry is that people might assume that taking an aspirin today will protect them from cancer tomorrow. In reality, any potential preventive effect takes over a decade to appear, if it appears at all, while the bleeding risk begins immediately.'
Previous evidence has indicated potential benefits for individuals at high genetic risk of colorectal cancer, such as those with Lynch syndrome. Nonetheless, this review concentrates strictly on people at average risk, and the long-term evidence for them proved highly uncertain.
In recent years, researchers have investigated the role of over-the-counter medications, including ibuprofen and aspirin, in reducing bowel cancer. Aspirin functions by inhibiting the body's production of prostaglandins, hormones that transmit pain signals to the brain, thereby alleviating pain and reducing swelling and fever.
A 2025 trial published in the New England Journal of Medicine by Swedish researchers found that individuals who took a low daily dose of aspirin after tumour removal were half as likely to experience cancer recurrence over the subsequent three years. However, their role in the primary prevention of bowel cancer remains ambiguous and contentious.
Recommendations for Patients and Future Directions
The authors strongly advise that patients should not commence taking aspirin for cancer prevention without a thorough discussion with their healthcare professional regarding their personal bleeding risk. Dr Dan Cao, senior author, emphasised: 'This review reinforces that we must move away from a one-size-fits-all approach. Widespread aspirin use in the general population simply isn't supported by the evidence. The future lies in precision prevention – using molecular markers and individual risk profiles to identify who might benefit most and who is most at risk.'
The research team concludes that the narrative of aspirin for cancer prevention is considerably more intricate than previously thought, and the balance of benefits and harms evolves over time. Dr Zhang added: 'As scientists, we must follow the evidence where it leads. Our rigorous analysis of the highest-quality trials reveals that the 'aspirin for cancer prevention' story is more complex than a simple 'yes or no.' The current evidence does not support a blanket recommendation for aspirin use purely to prevent bowel cancer.'
Bowel cancer, also referred to as colorectal cancer, ranks among the most prevalent cancer types in the UK. Rates are increasing globally in individuals under 50, with scientists suspecting factors such as junk food, obesity, physical inactivity, and toxins produced by gut bacteria, though reasons remain unclear. Prevention typically involves adhering to a healthy lifestyle and undergoing routine screening tests.
