Cancer risk higher, still modest in some patients with IBD

Last Updated: 2015-05-27

By Larry Hand

NEW YORK (Reuters Health) - Some patients with inflammatory bowel disease (IBD) may have an increased, though still modest, risk of developing cancer, and it could depend on what medicines they take, according to a new analysis.

"Clinicians can tell patients that the overall risk of cancer in Crohn's disease patients is 1.6 times higher than the risk in the general population; however, the absolute risk of cancer is low, about 3.6% after 10 years of disease duration and about 10% after 20 years of disease duration," said Dr. Edward B. Loftus, of the department of gastroenterology and hepatology at the Mayo Clinic in Rochester, Minnesota.

"The overall risk of cancer in ulcerative colitis is not higher than that of the general population," he told Reuters Health by email.

Dr. Loftus and colleagues analyzed the records of 839 people living in Olmsted County, Minnesota, who were diagnosed with IBD between 1940 and 2004 and followed through 2011. Of those, 45% had Crohn's disease and 55% had ulcerative colitis (UC).

The researchers abstracted data on medications used to treat IBD and categorized them into four groups: sulfasalazine and 5-aminosalicylates (5-ASA), corticosteroids, immunomodulators (IMM), and anti-tumor necrosis factor-alpha (anti-TNF-alpha).

They categorized the cancers into seven groups, they explain in a report online May 9 in Mayo Clinic Proceedings: intestinal, tobacco-related, female reproductive organ, male reproductive, miscellaneous extraintestinal, hemotologic and melanoma (nonmelanoma skin cancer excluded).

The cumulative probability of a first cancer after IBD diagnosis was 3.8% by 10 years, 9.1% by 20 years, and 16.3% by 30 years. Overall, 109 patients with IBD developed 135 cancers during a median follow-up of 18.4 years.

Over 7,487 person-years, 47 Crohn's patients developed 58 cancers, accounting for a 57% higher risk of cancer compared with an age- and sex-matched general population. The increased risk reached statistical significance for women, with a standardized incidence ratio (SIR) of 1.7, but not for men.

The researchers found Crohn's patients to be at increased risk for hematologic malignancies (SIR 3.0) and melanoma (SIR 2.7), by category, and for small intestine (SIR 9.4), biliary tract (SIR) 21.2), Hodgkin's lymphoma (SIR 11.3), and brain (SIR 4.9), by site of cancer.

For UC patients, over a total follow-up of 9,822 person-years, the researchers found the 10-year cumulative probability of cancer after UC diagnosis to be 4.9%, with UC patients overall not having a higher risk of cancer than age- and sex-matched general population.

During follow-up, 62 UC patients developed 77 cancers, with women carrying a higher risk, compared with the general population and no increase in men.

By category, UC patients had a 2.7-fold increased risk for hematological malignancies and a numerically but not statistically higher risk of melanoma (SIR, 2.0). By site, UC patients had a significantly higher risk for biliary tract (SIR, 11.4) and a significantly lower risk for lung cancer (SIR, 0.3).

The researchers found an increased risk of melanoma in corticosteroid-treated patients (incident risk ratio 8.2) and IMM-treated patients (IRR 5.3).

"The increased risk of melanoma observed in current users of corticosteroids and IMMs decreased to baseline when not receiving treatment," they write.

"We did not find any significant increase in overall or category-specific cancer risk in patients with IBD treated with a 5-ASA, corticosteroid, IMM, or anti-TNF-a, except for an increase in the risk of hematologic malignant tumors in IMM-treated patients with IBD," they wrote.

"So, doctors and patients have to be vigilant, but these risks shouldn't preclude the use of effective therapies for Crohn's disease such as immunomodulators and biologics," Dr. Loftus said.

"Overall, I think this well-conducted study reports reassuring results for patients with IBD regarding risk of cancer," Dr. Nynne Nyboe Anderson, of the department of epidemiology research at the University of Copenhagen, Denmark, told Reuters Health by email.

"This is particularly encouraging for patients with ulcerative colitis as the development of colorectal cancers has been a main concern in these patients," said Dr. Anderson, an expert on IBD. "The observed increased risk of melanoma in patients on immunosuppressive treatment is in accordance with previous studies and highlights the importance of routine dermatological screening in patients treated with these drugs."

The Mayo Foundation for Medical Education & Research partly supported this research. The authors reported no study-specific disclosures.

SOURCE: http://bit.ly/1LsHZkt

Mayo Clin Proc 2015.