Lower Risk of Recurrence with a Higher Induction Dose of Mesalazine and Longer Duration of Treatment in Ulcerative Colitis: Results from the Dutch, Non-Interventional, IMPACT Study

The dose and duration of mesalazine treatment for ulcerative colitis (UC) is a potentially important determinant of effectiveness, with evidence suggesting that continuing the induction dose for 6-12 months may improve outcomes; however, real-world data are lacking. We assessed mesalazine use in Dutch clinical practice, including how differences in dose and duration affected UC outcomes.Adults with mild-to-moderate UC who received oral prolonged-release mesalazine de novo or had a dose escalation for an active episode were followed for 12 months in this non-interventional study (ClinicalTrials.gov identifier: NCT02261636). The primary endpoint was time from start of treatment to dose reduction (TDR). Secondary endpoints included recurrence rate, adherence, and work productivity.In total, 151 patients were enrolled, of whom 108 (71.5%) were newly diagnosed with UC. The majority (120; 79.5%) received a dose of ≥4 g/day. Nearly one-third (48; 31.8%) underwent dose reduction, with mean TDR being 8.3 months. Disease extent and endoscopic appearance did not influence duration of induction therapy, while TDR increased with higher baseline UCDAI scores. TDR was longer in patients without (mean 8.8 months) than with (4.1 months) recurrence, although not significantly (p=0.09). Patients on ≥4 g/day had a significantly lower chance of recurrence versus those on 2-<4 g/day (26.6% vs 62.5%, respectively; p=0.04). Longer treatment duration was associated with significantly reduced recurrence risk [hazard ratio >6 months vs 3-6 months: 0.19 (95%CI: 0.08-0.46); p<0.05], particularly for those on ≥4 g/day [0.15 (0.06-0.40) vs 0.26 (0.01-11.9) for 2-<4 g/day). Patients reported significantly increased work productivity, which was maintained throughout follow-up.Mesalazine was effective induction therapy, with treatment duration not meaningfully influenced by disease extent and endoscopic appearance at initiation. A higher induction dose of oral mesalazine (≥4 g/day) and longer duration of treatment (>6 months) was associated with a lower recurrence risk.