The use of biologic disease-modifying antirheumatic drugs (bDMARDs) has no medium-term effect on the risk for spinal fractures among patients with ankylosing spondylitis (AS), according to the results of a recent study conducted in Sweden and published in BMJ Open.
The investigators used prospectively collected electronic health data from the Swedish National Patient Registry, the Swedish Cause of Death Registry, and the Swedish Prescribed Drugs Registry. All participants were ≥18 years of age and were receiving treatment for AS at a healthcare facility. A total of 1352 patients with AS who received 1or more bDMARD prescription between 2005 and 2014 were compared with a matched untreated control group of 1352 individuals with AS (ClinicalTrials.gov identifier: NCT02840695). The main outcome measure was spinal fracture-free survival.
All the patients in the treatment group received bDMARD therapy (6166 person-years of treatment) and were followed for a median of 10 years after AS diagnosis (16,567 person-years of observation). In contrast, the 1352 patients in the control group did not receive bDMARD therapy more than once (16 person-years of treatment) and were followed for a median of 8 years (16,189 person-years). Those receiving bDMARD therapy were significantly older (P <.001), had significantly higher Charlson Comorbidity Index scores (P =.008), and received significantly more methotrexate (P <.001) than the control group.
Of the 2704 patients with AS, 91 sustained a fracture. Patients treated with bDMARDs experienced a spinal fracture after 12 years with the registered diagnosis of AS (95% CI, 6-12 years) compared with those not receiving bDMARD therapy, who sustained a spinal fracture after 11 years (95% CI, 5-12 years). With respect to fracture-free survival, there was no significant treatment effect with bDMARD therapy observed in either the univariate (hazard ratio [HR], 1.05; 95% CI, 0.70-1.59; P =.804) or the multivariate model (HR, 1.00; 95% CI, 0.66-1.51; P =.999). However, male sex (HR, 2.54; 95% CI, 1.48-4.36; P <.001) and Charlson Comorbidity Index score (HR, 3.02; 95% CI, 1.59-5.75; P <.001) were both significant contributors to a patient’s risk for fracture.
The investigators concluded that spinal fracture-free survival among patients with AS was not significantly affected by the use of bDMARD therapy. They did recognize that a longer observation period in this patient population might change the results of the study, as the follow-up of 10 years might have underestimated both the beneficial and the adverse effects of bDMARD therapy. Additional studies are warranted to validate the findings from the current study.
Robinson Y, Olerud C, Willander J. Do biological disease-modifying antirheumatic drugs reduce the spinal fracture risk related to ankylosing spondylitis? A longitudinal multiregistry matched cohort study. BMJ Open. 2017;7(12):e016548.