The occurrence of multiple treatment switches in axial spondyloarthritis. Results from five Nordic rheumatology registries

Objectives In axial spondyloarthritis (axSpA), switching between multiple biologic or targeted synthetic (b/ts-) DMARDs might indicate difficult-to-treat disease. We aimed to explore the occurrence of multiple switching in routine care axSpA patients using various definitions, and to identify associated clinical characteristics upon start of first b/tsDMARD (baseline). Methods Observational cohort study including patients with axSpA starting a first-ever b/tsDMARD 2009-2018 based on data from five biologic registries (Denmark/Sweden/Finland/Norway/Iceland). Comorbidities and extra-articular manifestations were identified through linkage to national registries. Multi-switching was defined in overlapping categories according to b/tsDMARD treatment history: treatment with >= 3, >= 4 or >= 5 b/tsDMARDs during follow-up. We explored the cumulative incidence of patients becoming multi-switchers with >= 3 b/tsDMARDs stratified by calendar-period (2009-2011, 2012-2013, 2014-2015, 2016-2018). In the subgroup of patients starting a first b/tsDMARD 2009-2015, baseline characteristics associated with multi-switching (within 3 years' follow-up) were explored using multiple logistic regression analyses. Results Among 8398 patients included, 6056 patients (63% male, median age 42 years) started a first b/tsDMARD in 2009-2015, whereof proportions treated with >= 3, >= 4 or >= 5 b/tsDMARDs within 3 years' follow-up were 8%, 3% and 1%, respectively. Calendar-period did not affect the cumulative incidence of multi-switching. Baseline characteristics associated with multi-switching (>= 3 b/tsDMARDs) were female gender, shorter disease duration, higher patient global score, comorbidities and having psoriasis but not uveitis. Conclusion In this large Nordic observational cohort of axSpA patients, multiple switching was frequent with no apparent time-trend. Clinical associated factors included gender, but also previous comorbidities and extra-articular manifestations illustrating the ongoing challenge of treating this patient group.