Colorectal cancer is the third most common malignancy and second leading cause of cancer related death in the Western world.1 In the United States (US), the lifetime risk for developing colon cancer is about 5.3%.2 Several risk factors for the development of colorectal cancer including family history, smoking, and diet have been documented. In addition to recognition and awareness, much research has focused on the prevention of colon and rectal carcinomas.
Numerous studies have demonstrated that aspirin use on a regular basis is associated with a lower risk of colorectal adenomas and cancer.3-5 Perhaps this is partly due to the ability of aspirin to inhibit COX-2, which normally promotes inflammation and cell proliferation. COX-2 is found to be overexpressed in tumor tissue and the majority of human colorectal cancers.
In a recent edition of the Journal of the American Medical Association, Chan and colleagues published results from their prospective cohort study examining the association between aspirin use and colorectal cancer survival. This study examined the following two nationwide cohorts of individuals with Stage I, II, or III colon cancer: The Nurses’ Health Study (NHS) and the Health Professionals Follow-up Study (HPFS).
The study included 1,279 participants with confirmed Stage I, II, or III colorectal adenocarcinoma. Pathological specimens were obtained for 76% of the HPFS group and 58% of the NHS group to assess COX-2 expression. Assessment of aspirin use including the number of tablets, dose, and reason for use was collected. Consuming aspirin tablets more than two times weekly was considered regular aspirin use. The primary outcome was to assess colorectal cancer-specific and overall mortality in patients using aspirin.
After a median follow up of 11.8 years, 193 (35%) deaths with 81 (15%) colorectal cancer-specific deaths occurred in the 549 participants who reported regular aspirin use. In the 730 participants who did not use aspirin, there were 287 (39%) deaths with 121 (19%) attributable to colorectal cancer. This equates to a 29% lower cancer-specific mortality (95% CI: 0.65 – 0.97) and 21% lower overall mortality (95% CI: 0.65 – 0.97) in the aspirin group compared to non-users. For the entire cohort, overall 5-year survival was 88% among aspirin users compared to 83% among non-users; corresponding 10-year survival rates were 74% and 69% respectively.
To further examine the benefits of aspirin initiated only after diagnosis, researchers examined post-diagnosis aspirin compared to pre-diagnosis aspirin use. Among the 719 participants who did not use aspirin before diagnosis, initiation post-diagnosis resulted in a HR for colorectal cancer specific mortality of 0.53 (95% CI: 0.33-0.86) and overall mortality 0.68 (95% CI: 0.51-0.92). However, those participants who used aspirin pre-diagnosis and continued aspirin post-diagnosis did not experience the same degree of benefit: the reduction in colorectal cancer-specific survival and overall survival was non-significant.
Finally, when researchers examined the subset of subjects with COX-2 overexpression, they discovered that regular aspirin use (started post-diagnosis) was associated with a 61% lower risk of colorectal cancer death and 38% lower risk of ...