Does aspirin or ibuprofen protect against colorectal cancer?
Aspirin demonstrably protects against colorectal cancer in people with a hereditary elevated risk (Lynch syndrome) and in people under 60 with an unhealthy lifestyle, but for older adults or people with a low baseline risk, the bleeding risks likely outweigh the benefits. Discuss it with your GP if you want to know whether this is worthwhile for you.
Aspirin demonstrably lowers the risk of colorectal cancer, but whether that benefit outweighs the downsides depends strongly on your age and health situation. The effect is greatest in people with Lynch syndrome, an inherited condition that sharply raises the risk of colorectal cancer. In a large randomised trial (CAPP2, 861 participants, followed for an average of 10 years), 9% of aspirin users still developed colorectal cancer, compared with 13% in the placebo group. That represents a risk reduction of 35%. Those who kept taking it for at least two years saw as much as 44% less colorectal cancer.
In the general population the absolute benefit is smaller. Large cohort studies involving more than 107,000 participants show that regular aspirin use lowers the ten-year risk from 2.95% to 1.98%, a difference of just under 1 percentage point. That is modest. People with an unhealthy lifestyle, such as smoking, being overweight, or getting little exercise, benefit the most: for them, 78 people need to take aspirin for ten years to prevent one case of colorectal cancer. For people with a healthy lifestyle, that number rises to nearly 900.
For people over 60, the picture is different. The US Preventive Services Task Force (USPSTF) concluded in 2022 that aspirin offers no net benefit as prevention for this age group, even in people with a genetically elevated risk. This is because the risk of bleeding, particularly in the gastrointestinal tract, carries more weight in older people. Aspirin for colorectal cancer prevention is therefore not recommended in older adults.
There is good evidence that ibuprofen and related anti-inflammatory drugs (NSAIDs) reduce the occurrence of both colorectal cancer and polyps, the early precursors of that cancer. However, their side-effect profile, gastrointestinal complaints and an increased risk of cardiovascular problems, makes them unsuitable as a preventive agent for the general population. Concrete figures for ibuprofen specifically were not reported in the available studies.
Based on one large RCT (CAPP2, Lynch syndrome), two large cohort studies (general population), the USPSTF guideline 2022, the ASPREE trial, and a systematic review on NSAIDs. Total estimated number of participants across all studies: more than 107,000 plus 861 plus additional cohort participants.