Patients who receive infliximab (IFX) combined with a thiopurine, for inflammatory bowel disease, have a better clinical response and less frequent immunization towards IFX than those treated with IFX alone. The benefits of combination therapy must be weighed against the risks of infection and cancer. We studied the association between the duration of combination therapy and the risk of treatment failure by two year from initiation.

Participants had Crohn's disease or ulcerative colitis and were in clinical and biological remission, 6 months after initiation of combination therapy. The risk of subsequent treatment failure (i.e., undetectable trough IFX levels and/or clinical relapse followed by surgical treatment or switch of maintenance treatment) was estimated using Kaplan–Meier method and adjusted Hazard Ratios (aHRs), in patients whohadreceived 6 to 11 months vs. 12 months or more of combination therapy. We performed a similar analysis in which the follow-up was started at discontinuation of the immunosuppressant.

Among 139 patients (48% women; median age 31.1), with a median follow-up of 18.9 months, we observed 26 treatment failures (including 15 patients with undetectable trough IFX levels). After adjustment for gender and type of immunomodulator, a shorter duration of combination therapy was not associated with a higher risk of treatment failure (aHR=0.42; 95% confidence interval (95%CI): 0.13–1.40; p=0.16). When the follow-up was started at discontinuation of the immunosuppressant, a combination therapy of 6–11 months was associated with a numerically lower risk of treatment failure as compared with a longer combination therapy (HR=0.12; 95%CI: 0.01–1.05; p=0.055).

Our results do not show any benefit for continuation of combination therapy for more than 12 months after achieving clinical remission in IBD patients.