Daily aspirin use does not offer a quick or reliable way to prevent bowel cancer in the general population and carries immediate risks of serious bleeding, according to a new Cochrane review. The findings, which scrutinize the effectiveness of aspirin in cancer prevention, highlight significant concerns over its use as a preventive measure.
Bowel cancer, also known as colorectal cancer, ranks among the most common types of cancer worldwide. Prevention strategies typically emphasize maintaining a healthy lifestyle and undergoing routine screening tests. In recent years, researchers have explored the potential of nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin, in reducing bowel cancer incidence. However, their role remains uncertain and controversial.
Study Findings and Immediate Risks
Researchers from West China Hospital of Sichuan University analyzed 10 randomized controlled trials involving 124,837 participants. Their investigation aimed to determine whether aspirin or other NSAIDs could prevent colorectal cancer or precancerous polyps (adenomas) in individuals at average risk. The analysis found no suitable trials for non-aspirin NSAIDs, focusing exclusively on aspirin.
The review revealed that aspirin probably does not reduce bowel cancer risk within the first 5 to 15 years of use. While some studies suggested possible protective effects after more than 10–15 years, the certainty of this evidence remains very low. These potential long-term benefits stem from observational follow-up phases, where participants may have altered their aspirin use or started other treatments, introducing bias.
“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,” explains Dr. Zhaolun Cai, lead author.
The review also highlights clear evidence that daily aspirin use increases the risk of serious extracranial hemorrhage and likely raises the risk of hemorrhagic stroke. Although higher doses pose the greatest risk, even low-dose aspirin elevates bleeding risk, particularly for older adults and those with a history of ulcers or bleeding disorders.
Long-Term Benefits and Uncertain Evidence
Despite some evidence suggesting potential benefits for individuals at high genetic risk of colorectal cancer, such as those with Lynch syndrome, this review focuses on individuals at average risk. The long-term evidence for this group remains highly uncertain.
“My biggest worry is that people might assume that taking an aspirin today will protect them from cancer tomorrow,” says Dr. Bo Zhang, senior author. “In reality, any potential preventive effect takes over a decade to appear, if it appears at all, while the bleeding risk begins immediately.”
The authors caution that any potential long-term benefit must be weighed against the immediate and well-established risk of bleeding. They urge patients to consult healthcare professionals before starting aspirin for cancer prevention, emphasizing individual risk assessment.
Moving Towards Precision Prevention
The review underscores the need to move away from a one-size-fits-all approach in cancer prevention. Widespread aspirin use in the general population lacks evidence support, according to the authors. Instead, the future lies in precision prevention, utilizing molecular markers and individual risk profiles to identify who might benefit most and who is most at risk.
“This review reinforces that we must move away from a one-size-fits-all approach,” says Dr. Dan Cao, senior author. “Widespread aspirin use in the general population simply isn’t supported by the evidence.”
The research team concludes that the story of aspirin for cancer prevention is far more complex than previously believed. The balance of benefits and harms changes over time, necessitating a nuanced understanding of aspirin’s role in cancer prevention.
“As scientists, we must follow the evidence where it leads,” Dr. Zhang adds. “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.”
This development follows growing scrutiny of over-the-counter medications in preventive healthcare, highlighting the importance of personalized medical advice and evidence-based practices.
