Abstract Background Most patients with ulcerative colitis (UC) experience a mild-to-moderate disease course characterized by alternating periods of remission and relapse. However, data on the clinical features and treatment patterns of mild-to-moderate UC remain limited, and the role of early treatment escalation is not well understood. Methods This retrospective single-centre study utilized data from the Sir Run Run Shaw Hospital Inflammatory Bowel Disease Biobank in China, enrolling patients diagnosed with UC between January 1999 and April 2025 who had at least 1 year of follow-up. At diagnosis, patients were classified as having either mild-to-moderate or moderate-to-severe UC according to the Truelove and Witts’ criteria. Mild-to-moderate disease was defined as 6 bowel movements per day, with limited rectal bleeding and no signs of high inflammatory activity. Results A total of 1,751 patients (88.7% with mild-to-moderate activity at diagnosis) were included, with a median follow-up of 5.65 (IQR 2.99-9.69) years. Compared with patients with moderate-to-severe UC, those with mild-to-moderate disease more frequently had proctitis at diagnosis (36.5% vs. 0.7% rates after removing patients with unknown disease extent, p 0.001), were less often escalated to advanced therapies (biologics or novel small molecules) (27.7% vs. 54.5%, p 0.001) after a longer median interval (3.67 vs. 0.86 years, p 0.001), and showed better therapeutic outcomes, including a higher rate of clinical response to first-line advanced therapy (74.5% vs. 64.1%, p = 0.047) and a lower colectomy rate (5.6% vs. 24.2%, p 0.001). Given that 62.8% of patients with mild-to-moderate UC used only 5-aminosalicylates (5-ASA) throughout follow-up, we further assessed the compliance to UC treatment guidelines. The 4-week clinical response rate to initial 5-ASA was 85.1%, with the responders more likely to receive combined oral and topical 5-ASA rather than monotherapy. Among the nonresponders (14.9%), 64.9% did not undergo any treatment modification, while 19.6% had 5-ASA optimization and 15.6% escalated to upgrade therapies, including corticosteroids (73.0%), immunomodulators (2.7%), and advanced therapies (24.3%). Colonoscopy re-evaluation at 8-12 weeks was performed in only 4.5% of the patients. Conclusion Patients with mild-to-moderate UC at diagnosis displayed distinct clinical phenotypes and generally favourable long-term outcomes, most of whom achieved initial disease control on 5-ASA alone. Nonetheless, many patients continued to experience recurrent symptom flares, often accompanied by delayed treatment adjustments and insufficient monitoring, underscoring the need to improve the compliance to current evidence-based UC management guidelines. References: 1. Inflammatory Bowel Disease Group, Chinese Society of Gastroenterology, Chinese Medical Association Inflammatory Bowel Disease Quality Control Center of China. Chinese Guidelines on the Diagnosis and Management of Ulcerative Colitis (2023, Xi’an). Chin J Inflamm Bowel Dis. 2024;08(01):33-58. doi:10.3760/cma.j.cn101480-20240123-00017 2. Ko CW, Singh S, Feuerstein JD, et al. AGA Clinical Practice Guidelines on the Management of Mild-to-Moderate Ulcerative Colitis. Gastroenterology. 2019;156(3):748-764. doi:10.1053/j.gastro.2018.12.009 Conflict of interest: Ms. Yang, Wenjing: No conflict of interest Yao, Lingya: No conflict of interest Cao, Qian: No conflict of interest
Yang et al. (2026) studied this question.