This study aims to evaluate the long-term outcomes of discontinuing 5-ASA in UC and CD patients receiving stable biologic or immunomodulator therapy using a prospective cohort based in the Busan-Ulsan-Gyeongnam region. It seeks to determine whether discontinuing 5-ASA is a safe treatment strategy in modern IBD management.

In inflammatory bowel disease (IBD), 5-aminosalicylic acid (5-ASA) is widely used as a first-line treatment for ulcerative colitis (UC) and is still prescribed for Crohn's disease (CD). However, for patients who do not respond to conventional therapy, anti-tumor necrosis factor (anti-TNF) agents have become an effective alternative. This has led to ongoing debate about whether continued use of 5-ASA is necessary after transitioning to anti-TNF therapy.

Recent retrospective studies have reported that discontinuing 5-ASA after initiating anti-TNF therapy in UC and CD patients does not increase the risk of clinical adverse outcomes such as new steroid use, hospitalization, or bowel surgery. However, a study based on U.S. data had a median follow-up period of less than one year, making it difficult to assess long-term effects. Additionally, studies on relapse risk after discontinuing 5-ASA have identified younger age, extensive disease, and frequent relapses as risk factors, but detailed analyses for patients receiving anti-TNF therapy remain insufficient.

Another critical issue is the economic burden of continued 5-ASA treatment. In South Korea, the annual cost of the most commonly used 5-ASA formulations constitutes a significant portion of overall healthcare expenses. Discontinuing 5-ASA could reduce treatment costs, simplify therapy, improve patient adherence, and minimize adverse effects associated with polypharmacy. Regarding colorectal cancer (CRC) prevention, recent trends indicate a decreasing incidence of CRC in IBD patients. Since mucosal inflammation is considered a primary driver of CRC, additional 5-ASA use may not be necessary if mucosal healing is achieved through biologics or small-molecule therapies.

Accordingly, this study aims to evaluate the long-term outcomes of discontinuing 5-ASA in UC and CD patients receiving stable biologic or immunomodulator therapy.

Inclusion Criteria

1. Diagnosis

   o Patients diagnosed with ulcerative colitis (UC) or Crohn's disease (CD) based on standard diagnostic criteria, including clinical, endoscopic, and histologic findings.

2. Treatment Status

   • Patients who have been continuously treated with biologic agents (e.g., anti-TNF agents, integrin inhibitors, JAK inhibitors) or immunomodulators (e.g., azathioprine, methotrexate) for at least three months.
   • Patients who have been on a stable dose of 5-ASA (mesalamine) for at least three months before study enrollment.

3. Disease Activity

   o Patients in clinical remission for at least three months, as defined by the Mayo score for UC or the Crohn's Disease Activity Index (CDAI) for CD.

4. Age

   o Adults aged 19 years or older.

5. Informed Consent

   o Patients capable of providing written informed consent for study participation.

6. Compliance with Study Protocol

   o Patients who can adhere to the study protocol and visit schedule.

7. General Health Condition

   o Patients without severe medical conditions that could impact the study or patient safety, such as significant cardiac, renal, or hepatic diseases.

8. No recent medication changes

9. Patients who have not had any new prescriptions or dose adjustments of corticosteroids, antibiotics, or other medications that could affect IBD within a specified period (e.g., four weeks) before enrollment.

Exclusion Criteria

1. Patients with severe active UC or CD at the time of study enrollment.
2. Patients who have been recently hospitalized for IBD-related reasons or undergone IBD-related surgery within three months before enrollment.
3. Patients who have had dose modifications of biologics, immunomodulators, or corticosteroids for IBD within three months before enrollment.
4. Patients receiving concomitant therapy with other medications that may affect disease activity (e.g., additional anti-inflammatory agents, IBD-related antibiotics).
5. Patients with severe cardiac, renal, or hepatic disease or other medical conditions that could interfere with the study.
6. Pregnant or breastfeeding women.
7. Patients with known allergies or intolerance to 5-ASA or related medications.
8. Patients currently participating in another clinical study that may interfere with this study.
9. Patients unable to provide informed consent or unlikely to comply with the study protocol and visit schedule.
10. Patients with a history of non-response or intolerance to their current biologic or immunomodulator therapy.
11. Patients with a history of severe psychiatric disorders that may affect their ability to participate in the study.