Background: Increasing numbers of patients are receiving biologics to treat ulcerative colitis (UC).
We prospectively studied treatment outcomes including measurement of serum infliximab (IFX) concentrations and the titers of antibodies to IFX (ATI).
Methods: The study group comprised 21 patients with UC who received induction therapy with IFX.
Disease activity was evaluated according to the Seo index (severe, ≥220; moderate, 150–219; and mild, 121–149). Treatment response defined remission ≤120; response <150 or ≥70 lower than the value at the start of IFX. The remission and response patients were considered to have improved.
Endoscopic findings were evaluated using the Mayo endoscopic score (MES). MES of 0 was defined as mucosal healing.
Loss of response (LOR) was defined as the occurrence of flare-ups of symptoms after the induction of remission.
The following variables were studied: (1) improvement rates 14 and 54 weeks after starting IFX, (2) serum IFX concentrations and ATI rates at these times, (3) the mucosal healing rate at 54 weeks, (4) the rate of LOR and serum IFX concentrations at the time, (5) the rate of continuing treatment with IFX, and (6) the rate of surgery.
The rate of LOR, IFX continuation rate and surgery rate were calculated by the Kaplan-Meier method.
This study was approved by the ethics committee of our hospital (B13–156).
Results: (1) The Seo index at the start of IFX therapy was 207±45. The improvement rate was 62% at 14 weeks and 47% at 54 weeks.
(2) The serum IFX concentration was 2.9±2.3 μg/mL in patients with improvement and 3.0±2.2 μg/mL in patients without improvement at 14 weeks (NS) and was 7.0±4.4 μg/mL in patients with improvement and 1.0±0.4 μg/mL in patients without improvement at 54 weeks (p<0.05). The ATI rate was 5% and was found in a patient with improvement at 14 weeks.
(3) The MES of 0 at 54 weeks was 36%. The serum IFX concentration was 8.9±2.7 μg/mL in patients with an MES of 0 as compared with 1.3±0.8 μg/mL in patients with an MES of 2 or 3 (p<0.001).
(4) The rate of LOR was 32% at 30 weeks and 46% at 54 weeks. The serum IFX concentration was 1.8±1.9 μg/mL at the onset of LOR. The final serum IFX concentration in patients who remained in remission was 5.5±4.5 μg/mL. These values differed significantly (p<0.05).
(5) The IFX continuation rate was 86% at 14 weeks and 59% at 54 weeks.
(6) The surgery rate was 5% at 14 weeks and 15% at 54 weeks.
Conclusions: It was difficult to evaluate response to treatment at 14 weeks solely on the basis of the serum infliximab concentration and ATI.
Mucosal healing and LOR were related to the serum IFX concentration.
These variables can be indices at the time of treatment reassessment. Measurement of these variables is useful that therapy is performed efficiently.