cancer diagnosis and therapeutic strategies for the management of patients after tumor diagnosis were collected. A possible association between IBD therapy and malignancy risk, and the treatment and evolution of cancer were also reviewed. Results: Ninety six IBD patients (47 Crohn's disease, 47 ulcerative colitis, 2 unclassified colitis) and 107 tumors were studied. Mean age was 58±14 years, 57% males, 38% smokers, 25% with family history of cancer. Seventeen tumors (15.9%) were diagnosed in patients receiving treatment with thiopurines, 3 in patients on methotrexate (2.8%), 2 during anti-TNF- α therapy (1.9%), and 11 were identified in patients on combined therapy with an immunosuppressive (9 thiopurines and 2 methotrexate) and an anti-TNF- α drug (10.3%). The median duration of treatment was: 72 months for thiopurines (IQR 6-102) and 6 months for adalimumab or infliximab (IQR 2-13). After the diagnosis of cancer, IBD treatment was maintained in 8 (47.1%) patients on thiopurines and in 1 (11.1%) patient with combined therapy. In the remaining patients on immunosuppressive and/or anti-TNF- α drug (n=24), the treatment was withdrawn, and in 5 (20.8%) of these cases the therapy was reintroduced later in agreement with the Oncology team. We could not find an association between thiopurines/ anti-TNF- α drugs and malignancy risk. Regarding the evolution of cancer, 55 tumors (51.4%) were managed only with oncological surgery, 9 (8.4%) with chemotherapy, 2 (1.9%) with radiotherapy and 33 tumors (30.8%) with combined therapy. Of these therapies, 82.5% were curative and 17.5% were palliative intent treatments. Patients were followed-up for a median of 39 months (IQR 24-57) from tumor diagnosis. During this period, 15 patients died (15.6%) due to cancer (mean age= 66±13 years), 4 (4.2%) had tumor recurrence and 77 (80.2%) patients remained in remission. Conclusions: 1.) Thiopurine treatment is maintained in approximately half of IBD patients after a cancer diagnosis. In contrast, anti- TNF- α drugs are withdrawn in most cases. 2.) An association between these drugs and a higher cancer risk was not found in our series; these findings support the subsequent reintroduction of these therapies in selected patients, always in agreement with the oncolo- gist's recommendations. 211 A Pilot Study of Optimized Monotherapy With Infliximab for Patients With Inflammatory Bowel Disease Byron P. Vaughn, Manuel Martínez˜˜-Vazquez, Vilas Patwardhan, Alan C. Moss, William J. Sandborn, Adam S. Cheifetz Background: Combination therapy with infliximab (IFX) and an immunomodulator has been shown to be superior to IFX monotherapy for patients with inflammatory bowel disease (IBD). Presumably much of the benefit of combination therapy is decreased immunogenicity of IFX, which has been associated with secondary loss of response. IFX trough concentration testing is not routinely performed for patients who have responded to IFX. We describe our experience of optimizing IFX monotherapy through proactive measurement of IFX trough concentration and titration. Methods: In 2009, one of the authors (ASC) began proactively measuring IFX trough concentrations in patients with IBD who were in clinical remission with the intent to optimize the trough to a detectable concentration. In 2010 the goal trough concentration was changed to 5-10ug/ml. Patients on IFX monotherapy who had a trough concentration drawn over this time period with the intent of titrating to a target trough range were included. Charts were reviewed to ensure the intent of the IFX concentration was to optimize the IFX dose. Paired Wilcoxon Signed Rank test was utilized to assess for changes between initial and follow-up trough concentrations (p<0.05 considered significant). Results: Thirty-one patients met the criteria for "optimized monotherapy" with IFX. Crohn's disease was the predominant indication for IFX (84%). Twenty-six percent (8/ 31) were initially on combination therapy but deescalated to IFX monotherapy. Seven of those patients had an IFX concentration after stopping combination therapy and 4 were deemed low requiring an increase of IFX dose. Two patients developed transient low-level antibody to IFX (<10ug/ml), with resolved after dose escalation. The median duration on IFX was 175 week (IQR: 116, 304). The median first IFX trough concentration was 6ug/ ml (IQR: 3.2, 10.2). Thirty-five percent (11/31) underwent an escalation of IFX therapy after their initial trough concentration. Twenty patients had a follow-up IFX trough concentra- tion (nine of whom underwent a dose escalation) allowing for a paired analysis. Of those patients, the median initial IFX concentration was 4.2ug/ml compared to the follow-up concentration of 7.6ug/ml (paired Wilcoxon Signed Rank test, p=0.02, Figure 1). All patients were eventually titrated to an IFX trough concentration of > 3ug/ml and 83% (26/31) achieved a trough concentration of > 5ug/ml. None of the 31 patients stopped IFX therapy. Conclusion: Prospectively optimized monotherapy may be an alternative to combination therapy for patients with IBD on IFX. Our data suggests that patients who have routine trough concentration monitoring and dose adjustment to optimize IFX dose, can have a sustained response to IFX. This approach should be further evaluated in a prospectively controlled trial as an alternative to combination therapy for patients with IBD. S-55 AGA Abstracts 212 Serum CRP Is a Better Early Marker for Response to Infliximab Induction Therapy Than Fecal Calprotectin in Patients With Moderate to Severe Ulcerative Colitis Johannan F. Brandse, Jeroen M. Jansen, Paul A. Baars, M. Lowenberg, Cyriel Ponsioen, Gijs R. van den Brink, Geert R. D'Haens Background: Serum CRP and fecal calprotectin are established makers for response to infliximab (IFX) maintenance therapy in Ulcerative Colitis (UC). However early measurement and its predictive value for response to IFX induction in UC remain uncertain. We aimed to define the optimal timing of measurement and compare both markers for response to therapy. Methods: In this multicenter prospective observational study UC patients starting on IFX were included. Serum CRP and albumin and fecal calprotectin (Bühlmann ELISA) were measured at day 0,1,4,7,11,14,18,21,28,42 during the first 6 weeks of induction therapy and Clinical Colitis Activity Index was monitored weekly. Absence of response was defined as the need for higher dose infusion during induction or colectomy within 3 months. Endoscopic response was defined as improvement at week 6-8 endoscopy. Results: Fifteen UC patients (5/15 left-sided, 10/15 pancolitis and 14/15 Mayo endoscopic score 3) were included. All but one patients received IFX according to the regular induction regime of 5mg/kg at week 0,2,6 and 7/15 with concomitant thiopurines. Median (IQR) baseline serum CRP was 36 (3-96) mg/L, albumin 38 (30-41) g/L and fecal calprotectin 1800ug/g (647- 1800). Median (IQR) serum CRP at day 4 was 59 (30-96) mg/l for patient with absence of response (n=3) compared to 3.8 (1.3-11.3) for responders (n=12), P=0.01. Median (IQR) CRP at day 7 was 15.3 (2-35) mg/l for endoscopic non-responders (n=8) compared to 1.6 (0.8-3.4) mg/l for endoscopic responders (n=7), P=0.06. CRP of >25mg/l at day 4 seemed to be an optimal cut-off OR:175 ( 95%CI:2.9-10520, P<0.01) for predicting absence of response. A cut-off for serum CRP of >5mg/l at day 7 had an OR:23 (95%CI:0.99-556, P= 0.02) for predicting lack of endoscopic response. Both serum albumin and fecal calprotectin discriminated less or later between clinical and endoscopic response. Analysis of fecal samples was however limited by the upper detection limit of the test (1800ug/g). Conclusions: Serum CRP is a better early marker for response to infliximab therapy compared to fecal calprotectin or serum albumin in patients with Ulcerative Colitis. Optimal timing for measuring serum CRP seems to be day 4 and day 7 in order to predict absence of clinical or endoscopic response, with cut-off values of 25mg/l and 5mg/ml respectively. Larger numbers of patients are needed to confirm these findings. Markers that significantly discriminate between absence of response and response or endo- scopic response or non-response AGA Abstracts