Aspirin has a long-standing reputation as a low-cost, widely accessible medication for preventive care. Regular, long-term low-dose aspirin use has been associated with a lower risk of developing colorectal cancer (CRC) in some studies, particularly among higher-risk populations.
New evidence complicates this narrative, especially for broad population-level recommendations. Black people are disproportionately affected by CRC, with those under the age of 50 facing a higher incidence and mortality rates from the disease.
The latest findings reinforce the need for more individualized, risk-based decision-making rather than blanket aspirin use.
Aspirin has been recommended for CRC prevention because it has been shown to reduce long-term inflammation, inhibit tumor-promoting pathways, and promote beneficial gut bacteria.
As a nonsteroidal anti-inflammatory drug (NSAID), aspirin reduces prostaglandin production, which is involved in inflammation and tumor development. It may also interfere with tumor growth pathways, limit blood vessel formation that feeds tumors, and influence the gut microbiome.
Some research suggests aspirin may be particularly effective in tumors with PIK3CA gene mutations, which occur in about 30 percent of CRC cases, and may enhance immune system responses against cancer cells.
Earlier guidance from the US Preventive Services Task Force (USPSTF) suggested low-dose aspirin could reduce the risk of CRC by 40 percent in certain populations. However, updated 2022 recommendations removed colorectal cancer prevention as a primary reason for aspirin use, citing insufficient and inconsistent evidence.
Daily aspirin use does not offer a reliable way to prevent colorectal cancer, according to a review published online Feb. 26 in the Cochrane Database of Systematic Reviews.
Zhaolun Cai, M.D., from Sichuan University in Chengdu, China, and colleagues conducted a systematic literature review to understand the role of nonsteroidal anti‐inflammatory drugs, particularly aspirin, in the primary prevention of colorectal cancer.
Based on 10 randomized controlled trials (124,837 participants), the researchers found that aspirin probably results in little to no difference at a follow-up of ≥5 to <10 years on CRC incidence (hazard ratio [HR], 1.00; three studies; 26,702 participants; moderate-certainty evidence) and at ≥10 to <15 years (HR, 0.95; two studies; 42,412 participants; moderate-certainty evidence). At ≥15 years, aspirin may reduce CRC incidence slightly (HR, 0.78; three studies; 47,464 participants; very low-certainty evidence). In the shorter term, aspirin may increase CRC mortality at ≥5 to <10 years (HR, 1.77; one study; 19,114 participants; low-certainty evidence). In the longer term, impacts on CRC mortality were uncertain (≥10 years to <15 years: odds ratio [OR], 1.14; one study; 39,876 participants; low-certainty evidence; ≥15 years: OR, 0.74; five studies; 53,909 participants; very low-certainty evidence). Additionally, aspirin is associated with an increased risk for serious extracranial hemorrhage (risk ratio, 1.59; eight studies; 97,567 participants; high-certainty evidence) and hemorrhagic stroke (OR, 1.40; eight studies; 105,037 participants; moderate-certainty evidence).
“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,'” senior author Bo Zhang, M.D., also from Sichuan University, said in a statement. “The current evidence does not support a blanket recommendation for aspirin use purely to prevent bowel cancer.”
The findings reveal little to no difference in the use of aspirin for CRC prevention. The long-term benefit is weak, with low certainty that it will reduce patients’ risk of developing the disease.
However, the elevated risks, including bleeding and stroke, are high-certainty findings, which ultimately shift the risk-benefit balance.
The over-the-counter medication comes with its own risks, particularly for older patients, those taking anticoagulants, and those with uncontrolled hypertension. Taking daily low-dose aspirin could increase their risk of gastrointestinal and cranial bleeding.
With this in mind, adding aspirin to a patient’s treatment plan will require shared decision-making and individual risk. While the medication may not be appropriate for sole CRC prevention, it may still be beneficial for cardiovascular disease prevention in select patients.
Providers should carefully weigh bleeding risk against any potential long-term benefit, particularly in patients with multiple comorbidities or those already taking medications that increase bleeding risk.
Black patients are disproportionately burdened by colorectal cancer. They face a higher incidence and mortality rates, and develop the disease at a much earlier age than other racial and ethnic groups.
Several structural inequities contribute to these disparities, including screening access gaps, delayed diagnosis, medical mistrust, and systemic barriers.
These disparities underscore the need to prioritize proven strategies rather than relying on interventions with uncertain benefits.
Recommending daily aspirin for CRC prevention comes with its challenges, as some patients may develop an overreliance on the drug, potentially distracting them from proven interventions and creating false reassurance that it will prevent the cancer entirely.
Instead, clinicians can recommend what’s proven to work: screening, early detection, and lifestyle interventions.
The USPSTF recommends CRC screening for adults aged 45 to 75 years old. Screening may be recommended even earlier for high-risk patients.
Screening options include colonoscopy and stool-based tests, such as FIT and stool DNA testing, which may increase accessibility for some patients. Early detection through these methods significantly improves survival outcomes.
To address disparities in colorectal cancer, clinicians should deliver culturally competent patient education and be aware of the access barriers that Black people may face when seeking preventive care.
The latest research makes one thing clear: aspirin should not be routinely recommended solely for colorectal cancer prevention. Instead, clinicians should focus on evidence-based strategies such as screening and risk-based care, while ensuring these approaches are accessible and equitable for all patients.
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