High aspirin doses needed for colon benefit
Aspirin can reduce the risk of colon cancer and the recurrence of colorectal adenoma, but only at doses high enough to incur risk of GI complications, a new study shows (Gastroenterology. 2008;134:21-28).
For 18 years, researchers collected data on aspirin use and the diagnoses of colorectal cancer among 47,363 male health-care professionals 40-75 years old. The investigators found that those who took more than 14 tablets of 325-mg aspirin each week for 6-10 years reduced their risk of cancer by 21%. The benefit disappeared after four to five years of discontinuing aspirin therapy.
Taking such high doses over such a long period raises the risk of GI bleeding and other adverse events. As a result, state the researchers, “the general use of high-dose aspirin for cancer prevention by a healthy population cannot be recommended.” This is consistent with the conclusions of the U.S. Preventive Services Task Force.
Another study in the same issue of Gastroenterology (pp. 29-38) focused not on a healthy population but on 945 patients with a history of colorectal adenoma. Among these patients, high doses of aspirin had a strong benefit.
Investigators in England conducted a multicenter, randomized, double-blind trial of aspirin (300 mg/day) and folate supplements (0.5 mg/day) to prevent recurrence. Both regular aspirin and dietary folate had been shown to reduce the risk of colorectal neoplasia in observational studies.
In the new trial, aspirin but not folate reduced the risk of colorectal adenoma recurrence, “with evidence that aspirin could have a significant role in preventing advanced lesions.”