S1640 Outcomes of First-Line Anti-TNF Treatment in Ulcerative Proctitis Is Similar to Those With Left Sided Colitis: An Exploratory Study

Introduction: Ulcerative colitis (UC) is a chronic inflammatory bowel disease with variable disease distribution. Although anti-tumor necrosis factor (TNF) agents are well-established first-line therapies for moderate to severe UC, their role in the management of ulcerative proctitis (UP) is not well-described. Patients with UP are frequently excluded from clinical trials, limiting generalizability to this population. This study aimed to assess whether outcomes differ between patients with UP and left-sided colitis following initiation of TNF as first line advanced therapy. Methods: We conducted a retrospective cohort study of bionaive adult UC patients treated with TNF at a tertiary referral center between 2014 and 2023. Chart review confirmed disease extent at index colonoscopy and patients were stratified as having UP, defined as inflammation ≤20 cm from the anal verge, or left sided colitis, defined as inflammation extending >20 cm from anal verge but not proximal to the mid transverse colon. The primary outcome was a composite of clinical remission based on provider global assessment at 52 ± 4 weeks and drug persistence at 52 ± 4 weeks. Secondary outcomes included dose escalation of TNF, endoscopic response, biomarker trends, and adverse events. Baseline variables included age, sex, body mass index, albumin, C-reactive protein, fecal calprotectin, and concurrent UC therapies. Categorical data were compared by Chi-square tests or exact tests. Continuous data were compared by Wilcoxon rank sum tests. Logistic regression was conducted to test disease location effect on the outcome of interest adjusting for the baseline covariates. Results: Fifty patients met inclusion criteria (26 UP, 24 left-sided). Rates of the primary outcome were identical across groups (50%, P > 0.900). No significant differences were observed in dose escalations (42% proctitis vs 33% left-sided, P = 0.500), endoscopic response, or change in fecal calprotectin. Albumin was lower in the left-sided group (median 3.5 vs 4.05 g/dL, P < 0.001), but this did not correlate with outcomes. Multivariable analysis adjusting for baseline factors showed no significant association between disease location and treatment response. Conclusion: Patients with UP demonstrated comparable outcomes to those with left-sided colitis when treated with first-line TNF therapy in this exploratory study. These findings challenge the rationale for excluding UP patients from clinical trials and support their inclusion in future studies and treatment guidelines.