AB0408 FIXED-INTERVAL VERSUS ON-DEMAND RETREATMENT STRATEGY WITH RITUXIMAB IN RHEUMATOID ARTHRITIS: A RETROSPECTIVE COHORT STUDY
Authors: Lisa Schapink, Nathan den Broeder, Alfons den Broeder, Lise Verhoef
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background:</h3> Rituximab (RTX), a monoclonal anti CD20 B-cell antibody is safe and effective in the treatment of Rheumatoid Arthritis (RA). The most optimal retreatment strategy in responding patients is still unclear. A recent study by Chatzidionysiou et al suggests that RTX retreatment with Fixed-Interval (FI) strategy is better than retreatment with an On-Demand (OD) strategy. [1] However, whether FI treatment strategy is also superior in a treat to target setting is not known. At our centre (Sint Maartenskliniek, the Netherlands), patients were retreated with RTX using the FI strategy and the OD strategy, by discretion of the rheumatologist, and using treat to target of DAS28CRP &lt;2.9 in all patients. In the FI strategy, patients receive retreatment after a predefined fixed period, mostly every 6 months. In the OD strategy, patients receive retreatment in case they experience increase in disease activity. In our hospital, most of the OD strategy patients were switched to the FI strategy in 2014 based on best evidence at that time, enabling us to retrospectively compare effectivity of these strategies. <h3>Objectives:</h3> To compare the effectivity of retreatment of RA patients with RTX following the FI or OD retreatment strategy. <h3>Methods:</h3> Adult (≥18) RA patients (clinical diagnosis) who started RTX treatment (1 or 2 x 1000mg or 2 x 500mg intravenous) between 1-1-2008 and 1-6-2016 and received at least 3 infusion cycles were included. Patients were treated with either FI or OD strategy, or crossed over from OD to FI. For on demand treatment, RTX retreatment could be planned at the daycare within 2-4 weeks. Primary outcome was DAS28-CRP, secondary outcome was mean yearly dose of RTX. Baseline characteristics and follow up data (DAS28-CRP scores, information on RTX infusions, and steroid injections) were retrospectively extracted from patients' health records. A linear mixed model was used to analyse the influence of the strategies on DAS28-CRP score. Time since start of RTX, calendar year, RTX dose, intra-articular (IA) or intramuscular (IM) steroid injection &lt;6 weeks ago, concomitant csDMARD use at start of treatment and RF status were added to the model as fixed effects. Data was analysed using Stata 13.1. <h3>Results:</h3> 213 patients were included. 154 following FI strategy, 25 following the OD strategy and 34 switching from OD to FI. Median duration of follow up was 38 months (IQR: 23-64), with a median number of 8 (IQR 5-12) DAS28-CRP measurements per patient. Patient characteristics are shown in Table 1. The OD strategy was not associated with higher DAS28-CRP score compared to FI strategy: adjusted difference was 0.09 DAS28-CRP point (95% CI: -0.08 to 0.26). Regardless of used strategy, DAS28-CRP improved significantly both over year of treatment, and by time from the start of RTX treatment. Furthermore was rheumatoid factor positivity associated with an lower DAS28-CRP in all patients, with adjusted difference of - 0.37 (95%CI: - 0.60 to - 0.14). Average yearly RTX dose was 1899mg/yr (SD: 604) under the FI strategy and 1740mg/yr (SD: 732) under the OD strategy (95% CI difference: -336 to 34mg/yr). <h3>Conclusion:</h3> Retreatment of RA patients with a fixed interval strategy does not seem to lead to better disease control or more drug use compared to an on demand strategy. A possible explanation might be the use of treat to target in our centre. Our study suggests that either strategy might be chosen in shared decision making and following treat to target. <h3>References</h3> [1] Chatzidionysiou, et al. J Rheumatol. 2017 Feb;44(2):162-169. <h3>Disclosure of Interests:</h3> None declared