Among people with Lynch Syndrome, daily aspirin use may cut the risk of colorectal cancer in half. This result—based on longer follow-up of a study that initially found no benefit of aspirin—was published in The Lancet.
Lynch Syndrome, also known as hereditary nonpolyposis colorectal cancer (HNPCC), results from inherited mutations in genes involved in DNA mismatch repair. These mutations greatly increase the risk of developing colorectal cancer. In individuals with Lynch Syndrome, the average age at diagnosis of colorectal cancer is about 44 years, compared with 64 years in the general population. Overall, roughly 3% to 5% of all colorectal cancers are thought to result from Lynch Syndrome. Other cancers that are more common in Lynch Syndrome families include cancers of the endometrium (the lining of the uterus), ovary, small intestine, ureter, and renal pelvis.
Aspirin has been linked with a reduced risk of colon polyps in previous randomized trials, but the current trial is the first to focus on colorectal cancer as an outcome. The study—known as CAPP2—enrolled 861 people with Lynch Syndrome. Study participants received 600 mg per day of aspirin or a placebo. The study also explored the effect of resistant starch.
An earlier report from this trial, published in 2008, did not find a benefit of benefit of aspirin or resistant starch. Longer follow-up, however, has revealed a substantial benefit from aspirin. Patients have now been followed for an average of 56 months.
These results suggest that daily aspirin can reduce the risk of colorectal cancer in people with Lynch Syndrome. Aspirin does not replace other measures used to manage cancer risk in this population, but may be a useful addition. Because regular aspirin use has some risks, however, people should talk with their doctor before they begin using aspirin. Ongoing research will explore the optimal dose and duration of aspirin use for people with Lynch Syndrome. Doses lower than the 600 mg per day used in the current study may prove to be sufficient.
 Burn J, Gerdes A-M, Macrae F et al. Long-term effect of aspirin on cancer risk in carriers of hereditary colorectal cancer: an analysis from the CAPP2 randomised controlled trial. Lancet. Early online publication October 28, 2011.