Dr. Loftus and Dr. Sandborn urged their colleagues to keep this increased risk in perspective in counseling patients by focusing on the modest absolute increase in risk rather than the scarier-sounding relative risk. Notably, two-thirds of lymphomas in the French study occurred in patients not on thiopurines or anti-TNF agents.
“The most interesting thing to me is that we worry and worry about lymphoma, and guess what? In this study and in multiple other studies, the majority of lymphomas occurring in IBD patients have nothing to do with their medications. They’re due to the usual risk factors for lymphoma, which include age and male gender,” Dr. Loftus observed.
The French study included more than 189,000 IBD patients followed for a median of 6.7 years, during which 336 cases of lymphoma occurred. The incidence rate was 0.26 cases per 1,000 person-years in unexposed patients. The rate was significantly higher at 0.54 per 1,000 person-years in those on thiopurine monotherapy, increased to a similar extent at 0.41 cases per 1,000 person-years in patients on anti-TNF monotherapy, and 0.95 per 1,000 person-years in those on combination therapy.
In a multivariate analysis, the lymphoma risk was an adjusted 2.6-fold greater in patients exposed to thiopurine monotherapy than in unexposed patients, 2.41-fold greater in patients exposed to anti-TNF monotherapy, and 6.1-fold greater in those exposed to combination therapy.