Immunosuppressive therapies for inflammatory bowel disease do not appear to be implicated in the increased risk for melanomas and hematologic malignancies seen in these patients, based on the results of a large database analysis and a separate meta-analysis published in the February edition of Clinical Gastroenterology and Hepatology.
The first study, based on a nationwide population-based cohort analysis conducted in Denmark, found that patients with inflammatory bowel disease (IBD) are at increased risk for cancer, in particular hematologic malignancies and melanoma at standardized incidence ratios of 1.9 and 1.4, respectively.
The second study, based on a systematic review and meta-analysis of the medical literature, found a diagnosis of Crohn’s disease or ulcerative colitis was associated with a 37% increase in the risk of developing melanoma. Melanoma risk was higher in studies performed before the introduction of biologic therapies in 1998, but not in those studies performed after 1998.
For the first study, researchers led by Dr. Michael D. Kappelman of the division of pediatric gastroenterology at the University of North Carolina at Chapel Hill used health care databases to identify patients in Denmark with a diagnosis of Crohn’s disease or ulcerative colitis from 1978 through 2010 (doi: 10.1016/j.cgh.2013.03.034). They followed the patients until the first occurrence of cancer, death, or emigration and used standardized incidence ratios (SIRs) to compare cancer incidence in patients with IBD with that expected in the general population.
"If immunosuppressive medications reduce the risk of gastrointestinal malignancy by suppressing intestinal inflammation but increase the risk of extraintestinal malignancies, IBD patients may be trading off one set of risks for another," the researchers wrote. "We therefore sought to evaluate both intestinal and extraintestinal malignancies comprehensively, as well as the occurrence of any invasive cancer, in a nationwide cohort of patients with IBD in Denmark."
The analysis included 13,756 patients with Crohn’s disease and 35,152 patients with ulcerative colitis who were followed up for a mean of nearly 8 years. After the exclusion of cancers diagnosed within 1 year of IBD diagnosis, 772 cases of invasive cancer occurred among patients with Crohn’s disease (SIR 1.3) and 2,331 occurred among patients with ulcerative colitis (SIR 1.1). Diagnosis of Crohn’s disease was weakly associated with gastrointestinal cancers (SIR 1.2) and extraintestinal cancers (SIR 1.3), with the strongest associations for hematologic malignancies (SIR 1.9), smoking-related cancers (SIR 1.5), and melanoma (SIR 1.4). Associations between ulcerative colitis and gastrointestinal and extraintestinal cancers were weaker (SIR of 1.1 for both).
Dr. Siddharth Singh
The excess risk of cancer in patients with Crohn’s disease "largely is owing to extraintestinal cancers, particularly hematologic malignancies and melanoma, both of which may be related to immune suppression, and smoking-related cancers," the researchers concluded. They added that their study "provides reassuring data that the decreasing risk for gastrointestinal malignancy observed here ... has not been offset by a concomitant increase in the risk of extraintestinal or hematologic malignancies. These findings suggest that changes in the medical and surgical treatment of IBD and/or other secular trends have not substantially impacted cancer relative risk on a population basis."
The study was supported in part by grants from the National Institute for Diabetes and Digestive and Kidney Diseases, the Karen Elise Jensen Foundation, and the Clinical Epidemiological Research Foundation.
In the second study from the journal, researchers led by Dr. Suddharth Singh of the division of gastroenterology and hepatology at Mayo Clinic, Rochester, Minn., conducted a systematic literature search through March 2013 for cohort studies showing incident melanoma after IBD diagnosis and an estimate of incident rate ratio or standardized incidence rate. Case reports or case series were excluded (doi: 10.1016/j.cgh.2013.04.033).
Of the 838 studies identified, 12 that comprised 172,837 patients with IBD were included in the final analysis. The pooled crude incidence rate of melanoma among patients in the 12 studies was 27.7/100,000 person-years. This translated into a 37% increase in the risk of melanoma (risk ratio of 1.37). The increase was observed independently in the patients with Crohn’s disease (RR 1.51) and in those with ulcerative colitis (RR 1.23). In addition, the risk of melanoma was higher in studies conducted prior to 1998, when biologic therapies were introduced (RR 1.52), but not in those conducted after 1998 (RR 1.08).
"The risk of melanoma has been shown to be increased in immunosuppressed patients, including patients with a prior solid organ transplant, lymphoma, and patients with human immunodeficiency virus infection and acquired immunodeficiency syndrome. It is possible that the increased risk of melanoma observed in patients with IBD may be related to underlying immune dysfunction in these patients, resulting in altered tumor surveillance" the researchers wrote.
