Treating inflammatory bowel disease (IBD) with azathioprine or 6-mercaptopurine (6-MP) increases the risk of lymphoma by about fourfold, according to a report in the August issue of Gut. Still, the absolute risk of this malignancy is small and, for most patients, the benefits of these agents outweigh the risks.
“The IBD patients in our meta-analysis who were treated with these drugs were at elevated risk for lymphoma,” senior author Dr. J. D. Lewis, from the University of Pennsylvania in Philadelphia, told Reuters Health. “However, from this analysis, it’s impossible to tell if the drugs themselves are to blame or if it’s just a consequence of the underlying disease.” Dr. Lewis emphasized that “even if the elevated risk was strictly due to the medications, for most patients with Crohn’s disease, and probably also ulcerative colitis, the benefits of therapy would outweigh the potential harms.” He estimated that the absolute risk of lymphoma is around 45 to 60 cases per 100,000 patients treated per year, but added that the risk does increase with age. Previous reports have shown an elevated lymphoma risk when azathioprine or 6-MP is used to treat other conditions, such as rheumatoid arthritis. With IBD, however, lower doses of these drugs are often used, so it was unclear if this risk applied. The few studies that have addressed this topic have been underpowered and have yielded conflicting results.In an effort to reach more definitive conclusions, Dr. Lewis’ team conducted a meta-analysis of studies that looked at the cancer risks of azathioprine or 6-MP therapy for IBD. Five studies that addressed the risks of azathioprine and one that evaluated 6-MP were included in the analysis.In the pooled analysis, treatment with these immunomodulators was associated with a 4.18-fold increased risk of lymphoma, the investigators point out. Dr. Lewis acknowledged that the findings do not suggest that a change in clinical practice is currently warranted. A change might be indicated if an immunomodulating agent that doesn’t raise the risk of malignancy ever becomes available, he added.(Source: Gut 2005;54:1121-1125: Reuters Health: Anthony J. Brown, MD: Oncolink: July 2005.)