MONDAY, Oct. 26 (HealthDay News) -- Inflammatory bowel disease (IBD) patients who are being treated with immunosuppressive medications may be at increased risk for non-melanoma skin cancer, a new U.S. study says.

Researchers analyzed data on 26,403 Crohn's disease patients and 26,974 patients with ulcerative colitis in order to evaluate how the use of immunosuppressive and biologic medications to treat IBD affected non-melanoma skin cancer risk.

The study found that the incidence of non-melanoma skin cancer was higher in IBD patients than in a control group. Recent use (within 90 days) of any immunosuppressive medication was associated with greater risk of non-melanoma skin cancer (adjusted odds ratio 3.28), as was recent use of the thiopurine class of immunosuppressive medications (adjusted odds ratio 3.56) and recent use of biologic medications in Crohn's disease patients (adjusted odds ratio 2.07).

Persistent use of any immunosuppressive medication, which was considered use for over one year, was strongly associated with non-melanoma skin cancer (adjusted odds ratio 4.04), the study authors noted. The association was even stronger with persistent use of thiopurine medications (adjusted odds ratio 4.27). In Crohn's disease, persistent use of biologic medications was also associated with a raised risk (adjusted odds ratio 2.18).

"The increased risk of [non-melanoma skin cancer] in patients with IBD is likely related to the immunosuppressive medications used to treat the disease, although we can't rule out changes to the immune system itself as a result of IBD as contributing to this risk," said study leader Dr. Millie Long, of the University of North Carolina at Chapel Hill.

"In patients on immunosuppression therapy after organ transplant, previous studies have shown a clear association with [non-melanoma skin cancer]. Other studies have demonstrated that azathioprine, which is in the thiopurine class, can increase the photosensitization of human skin," she noted.

Long concluded that the study "demonstrates that patients with IBD on immunosuppression may also be at risk for [non-melanoma skin cancer]. As a result, our long-term management plans for IBD patients should stress the daily use of broad-spectrum sunscreen and increased awareness of [non-melanoma skin cancer] to help to prevent complications."

The study was scheduled to be presented this week at the annual scientific meeting of the American College of Gastroenterology, in San Diego.

More information

The American Academy of Family Physicians has more about inflammatory bowel disease.