5-aminosalicylate maintenance is not superior to no maintenance in patients with newly diagnosed Crohn's disease-A nationwide cohort study.

BACKGROUND: 5-aminosalicylates (5-ASA) are widely used in Crohn's disease (CD) despite guidelines advising otherwise. We aimed to assess in nationwide study the outcomes of first-line 5-ASA maintenance therapy (5-ASA-MT) compared with no maintenance treatment (no-MT) in patients with newly diagnosed CD.

METHODS: We utilised data from the epi-IIRN cohort, including all patients with CD diagnosed in Israel between 2005 and 2020. Propensity score (PS) matching was utilised to compare outcomes in the 5-ASA-MT versus no-MT groups.

RESULTS: Of the 19,264 patients diagnosed with CD, 8610 (45%) fulfilled the eligibility criteria (3027 [16%] received 5-ASA-MT and 5583 [29%] received no-MT). Both strategies declined over the years; 5-ASA-MT from 21% of CD patients diagnosed in 2005 to 11% in 2019 (p < 0.001) and no-MT from 36% to 23% (p < 0.001). The probability of maintaining therapy at 1, 3 and 5 years from diagnosis: 5-ASA-MT-78%, 57% and 47% and no-MT-76%, 49% and 38% respectively (p < 0.001). PS analysis successfully matched 1993 pairs of treated and untreated patients and demonstrated comparable outcomes of time to: biologic (p = 0.2), steroid dependency (p = 0.9), hospitalisation (p = 0.5) and CD-related surgery (p = 0.1). Rates of acute kidney injury (5.2% vs. 3.3%; p < 0.001) and pancreatitis (2.4% vs. 1.8%; p = 0.03) were higher in the 5-ASA-MT group compared with the no-MT group but after PS matching the rates of adverse events were similar.

CONCLUSION: First-line 5-ASA monotherapy was not superior to no-MT but associated with a slightly higher rates of adverse events, while both strategies have declined over the years. These findings suggest that a subset of patients with mild CD may be offered a watchful waiting approach.