Oct. 26, 2009 -- Patients with inflammatory bowel disease or IBD may be at an increased risk for getting skin cancer, according to a study presented at the American College of Gastroenterology's annual meeting in San Diego.
The risk appears to be linked to medications to control IBD, says researcher Millie Long, MD, MPH, at the University of North Carolina, Chapel Hill.
And some medications boost risk more than others, she found.
''Patients on immunosuppressant medications, particularly of the thiopurine class, have an increased risk of skin cancer, greater than three times, compared to patients with IBD who do not use these medications," Long tells WebMD. Purinethol and Imuran are examples of thiopurines.
While previous research by others has also found an increased risk of skin cancer in IBD patients, Long says her study is thought to be one of the first to zero in on specific medications.
For the study, Long and her colleagues first looked at the records of 26,403 IBD patients with Crohn's disease and 26,974 with ulcerative colitis, evaluating their records from 1996 through 2005. Each of the patients was matched according to age, sex, and region of the country with records from three patients who did not have IBD.
IBD is used to refer to both ulcerative colitis and Crohn's disease. While different parts of the gastrointestinal tract are usually affected, both diseases involve chronic inflammation, resulting in symptoms such as diarrhea, rectal bleeding, and abdominal cramps. (IBD is different than IBS or irritable bowel syndrome, which does not involve intestinal inflammation or damage.)
The cause of IBD isn't known, but experts say it is related to the immune system responding to the body inappropriately.
Overall, Long found that the risk of getting a nonmelanoma skin cancer was 1.6 times higher for the IBD patients than patients in the comparison group.
Nonmelanoma skin cancers include squamous cell and basal cell skin cancers. About 1 million people in the U.S. are diagnosed annually with these cancers, which are extremely curable if detected early.
IBD Patients Only
Long's team took a closer look at just the IBD patients in the study and the specific medicines they took. Several types of medications are used to treat IBD, with a goal of decreasing excess activity of the immune system. Long compared 742 IBD patients with skin cancer to 2,968 IBD patients without skin cancer.
Among the findings:
- Use of any immunosuppressant medicines in the past 90 days increased risk of skin cancer by 3.2, she found.
- Thiopurine medicine boosted the risk the most, followed by biologics. Among thiopurines are mercaptopurine (Purinethol) and azathioprine (Imuran). Biologics include infliximab (Remicade) and others.
- Long-term use, defined as a year or more, was more strongly associated with risk of skin cancer. Those who had taken the thiopurine medicines for more than a year, for instance, had a fourfold increased risk of skin cancer; Crohn's patients on long-term biologics had a twofold increased risk.
Exactly why the medications seem to boost the risk of nonmelanoma skin cancers, Long says, isn't certain.
Other research has suggested that the medications may increase the sensitivity of skin to sunlight, she says.
Changes to the immune system itself as a result of the IBD can't be ruled out, however, as a factor increasing skin cancer risk, she says.
The new study results are no surprise, says Sunanda Kane, MD, MSPH, associate professor of medicine at the Mayo Clinic in Rochester, Minn., a gastroenterologist who focuses her research and clinical work on IBD.
''We have always sort of suspected that perhaps the common cancers are even more common in patients who are chronically immunosupressed."
The findings should get patients and doctors thinking differently, she says, about who is at risk for skin cancers. "Historically we think of skin cancer patients as Caucasians from the Northern Hemisphere," she says. But many others are also at risk, she says.
''People should not change their medications whatsoever because of these findings," Long says. The take-home message for patients, she says, is to be aware of the risk and keep a closer eye on their skin as well as adhere to safe sunning practices such as wearing a broad-spectrum sunscreen.
Deborah S. Sarnoff, MD, vice president of the Skin Cancer Foundation, agrees: ''Patients taking immunosuppressive medication for prolonged periods need to be extra vigilant about checking their skin and practicing sun safety every day."
Considering both benefits and risks of drugs is important, says Brian Kenney, a spokesman for Centocor, which makes the biologic Remicade.
"It is important for people living with Crohn's disease or ulcerative colitis, and physicians treating these diseases, to remain vigilant throughout the course of treatment, regardless of the type of immunosuppressive therapy," Kenney says.