Inflammatory Bowel Disease Drugs Linked to Cancer Risk

The results of a new French study suggest that thiopurine drugs, which are commonly used to treat inflammatory bowel disease (IBD), could increase the risk of cancer from viral infections.

The study results were released Monday in the online edition of the medical journal The Lancet, and will appear in an upcoming issue. Researchers found that patients who took thiopurine drugs had five times the risk of developing forms of cancer related to viral infections than those who did take the drugs.

Thiopurine is sold by GlaxoSmithKline under the brand name Imuran and by Salix under the brand name Azasan. The drug is also sold as a generic known as azathioprine. The drug suppresses the immune system and is approved for use by kidney transplant patients to prevent rejection of the new kidney. However, it is prescribed heavily off-label for the treatment of IBD and multiple sclerosis.

Researchers from a Paris, France hospital, Saint-Antoine, examined data involving 19,486 patients with inflammatory bowel disease. Over a 35-month period, there were 23 cases of cancer typically associated with viral infections, known as malignant lymphoproliferative disorders (LD).

The French researchers found that the rate of developing LD, such as non-Hodgkin’s lymphoma, was 0.90 per 1,000 patient-years for people taking thiopurine drugs, as compared to 0.26 per 1,000 patient-years for those who had never taken the drugs. The study also found increased risk in male patients, older patients, and those who had suffered from IBD for prolonged periods of time.

The researchers noted that the cumulative risk for young patients remained low, and indicated that the benefits of the drugs still appear to outweigh the risk of cancer. However, they indicated that further research needs to be done to determine the risk for older patients and patients who have undergone thiopurine treatment for extended periods of time.