Allopurinol, a common gout drug may also offer some protection against colorectal cancer

A commonly prescribed drug used to treat gout may also offer some protection against colorectal cancer, according to a new study from researchers at the University of Michigan and in Israel.

The study found that patients taking allopurinol for at least five years experienced a two-thirds reduction in risk from colorectal cancer. It was reported during the American Association for Cancer Research Third Annual International Conference on Frontiers in Cancer Prevention Research in Seattle.

Allopurinol warrants further investigation in chemoprevention clinical trials of colorectal cancer, said Gad Rennert, M.D., Ph.D., director of the CHS National Cancer Control Center and Technion Public Health Forum in Haifa, Israel, who led the investigation with Stephen Gruber, M.D., MPH, Ph.D. from the University of Michigan Comprehensive Cancer Center.

Results were based on the analysis of 1,781 patients from Northern Israel who were prescribed allopurinol and enrolled in the Molecular Epidemiology of Colorectal Cancer (MECC) Study group between 1998 and 2004. Use of the drug was measured by a structured, in-person interview, with responses matched to computerized prescription records.

The study took into consideration other known risk factors for colorectal cancer, including aspirin or other NSAID use, first-degree family history for colorectal cancer, ethnicity, sports activity and vegetable consumption.

Allopurinol is thought to work by blocking the action of xanthine oxidase, the enzyme responsible for excess uric acid, the culprit in gout. This enzyme also produces the superoxide that promotes oxidative stress, which has been linked to DNA damage and potentially cancer.

As such, allopurinol acts as an antioxidant, one of many chemicals that reduce or prevent oxidation, thus preventing cell and tissue damage resulting from free radicals in the body.

Previous studies have focused on using antioxidants, mainly of nutritional origin, to reduce the risk of cancer. This approach represents another potential strategy that requires further investigation, says Gruber, assistant professor of Internal Medicine at the U-M Medical School.

In addition to Rennert and Gruber, other scientists on the research team included Joseph B. Bonner from the U-M Health System; and Ronit Almog, Hedy S. Rennert, and Marcelo Low from Technion and Clalit Health Services National Cancer Control Center in Haifa.