An important health benefit of aspirin is the prevention of cancer of the colon and the rectum. The US Preventive Services Task Force (USPSTF) has recommended aspirin use to reduce the risk of developing colon cancer, particularly for those patients with advanced adenomas that were found during a colonoscopy. An estimated 40% of people, without excess bleeding risk and who are regularly taking long-term aspirin, are showing a reduction of colon cancer risk. The benefit is seen especially in patients who have been using aspirin for over 10 years. Additionally, patients 50-59 years old saw the most benefit from using aspirin. Older persons are less likely to realize this benefit than younger people. However, the potential for this benefit is still possible for selected older people.
A recent study involving 84 patients found that only about 40% of patients with biopsy-proven advanced polyps are taking aspirin as recommended. The authors looked at patients who were considered a higher cancer risk because they had, at screening colonoscopy, advanced colorectal adenomas (defined as adenoma polyps 1 cm or larger in size or with villous histology, high-grade dysplasia or invasive cancer). The average age was 66 years with a range from 41 to 91 years. The patients were surveyed and found that 60% were not following the USPSTF recommendations.
The reasons for the low compliance with the USPSTF aspirin recommendations was not clear from the report and the authors recommended discussion of the use of aspirin with their physicians. Among physicians, there is often concern that aspirin use can increase the risk of bleeding. There is good evidence that the risk for GI bleeding (bleeding in the stomach or intestines), with and without aspirin use, increases with age. According to the USPSTF, being an older male is an important risk factor for GI bleeding. Other factors that increase the risk for bleeding include upper GI tract pain, GI ulcers, blood thinning medication use, and uncontrolled hypertension.  Nonsteroidal anti-inflammatory drug therapy combined with aspirin use may also increase the risk for serious GI bleeding compared with aspirin use alone.
The risk for serious GI bleeding in men is about twice that in women.  These risk factors increase the risk for bleeding substantially and should be considered in the overall decision about whether to start or continue aspirin therapy. Unfortunately, there is no evidence that enteric-coated or buffered formulations reduce the risk of serious GI bleeding. The USPSTF concluded that the benefits were worth the risk.
As always, it is important for each person to weigh the benefits and risks of any medication, but the potential benefits in the reduction of cancer risk should encourage careful consideration.