Top line:
New data suggest that aspirin may be more effective at preventing colorectal cancer (CRC) in people with unhealthy lifestyles, particularly smokers who are overweight.
Methodology:
Aspirin is an established agent for CRC prevention. It is unclear whether people with more lifestyle risk factors derive greater benefit from aspirin. Researchers analyzed regular aspirin use (defined as taking two or more standard 325 mg tablets per week) using long-term follow-up data from 63,957 women from the Nurses' Health Study and 43,698 men from the Health Professionals Follow-up Study. They calculated a healthy lifestyle score for each participant based on body mass index (BMI), alcohol intake, physical activity, diet, and smoking, with higher scores corresponding to a healthier lifestyle. Results included multivariate-adjusted 10-year cumulative incidence of CRC, absolute risk reduction (ARR) with aspirin use, and the number needed to treat associated with regular aspirin use by lifestyle score.
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Over 3 million person-years of follow-up, 2544 new cases of CRC were recorded. The 10-year cumulative incidence of CRC was 1.98% in regular aspirin users and 2.95% in non-users, with an ARR of 0.97%. The ARR associated with aspirin use was highest in people with the unhealthiest lifestyle scores and gradually decreased with healthier lifestyle scores (P < .001 for additive interaction). The ARR from 10 years of aspirin use in people with the unhealthiest lifestyle scores (0–1) was 1.28%, whereas the ARR in people with the healthiest lifestyle scores (4–5) was 0.11%. The number of patients who needed to be treated with aspirin for 10 years to prevent one CRC case was 78 in people with the unhealthiest lifestyles compared with 909 in people with the healthiest lifestyles. Among the individual components of the healthy lifestyle score, higher BMI and smoking were associated with a greater reduction in CRC risk with aspirin use.
Exercise:
“These results support the use of lifestyle risk factors to identify individuals who may have a more favorable risk-benefit profile for cancer prevention with aspirin,” the authors write.
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The study, led by Daniel R. Shikavi, M.D., Ph.D., of Massachusetts General Hospital in Boston and Harvard Medical School, was published online in JAMA Oncology.
Limitations:
The study population consisted primarily of white health professionals, which may limit the generalizability of the study findings. Lifestyle factors and aspirin use were self-reported and subject to measurement error. The study did not systematically evaluate adverse outcomes that may be attributable to aspirin use or the presence of known hereditary cancer syndromes.
Disclosure:
This study received no commercial funding. The authors have no relevant conflicts of interest.
