COPENHAGEN — Treatment with a tumor necrosis factor inhibitor produced a 63% clinical response rate in 842 ankylosing spondylitis patients who were treated for a median of more than a year in Denmark.
The Danish experience also showed that women and patients with higher disease activity at baseline were the least able to remain on treatment with a tumor necrosis factor (TNF) inhibitor, Dr. Bente Glintborg said at the annual European Congress of Rheumatology.
The registry data also documented an 8% rate of patients who stopped TNF inhibitor treatment because of adverse effects, said Dr. Glintborg, a researcher at Gentofte (Denmark) Hospital.
Dr. Glintborg and her associates used data collected by DANBIO, a registry begun in 2000 of patients treated with a biologic drug in Denmark. Through November 2008, the registry included 909 patients with ankylosing spondylitis who began first treatment with a TNF inhibitor.
Follow-up data were available for 842 of these patients. Their average age was 41 years (range, 32-50 years), their median disease duration when starting the TNF inhibitor was 5 years (range, 1-13 years), and 28% were women. Roughly half received infliximab (Remicade), about a quarter got adalimumab (Humira), and about 15% received etanercept (Enbrel), with the remaining patients receiving another drug. Patients were followed for a median of 437 days (range, 161-996 days).
TNF inhibitor treatment improved disease activity. BASDAI (Bath Ankylosing Spondylitis Disease Activity Index) scores dropped from an average of 59 at baseline to 21 after a year of treatment among the 644 patients who were assessed with the BASDAI at baseline.
The Bath AS functional index and metrology index, as well as a visual analog scale global assessment, all showed similar declines with treatment. Serum levels of C-reactive protein fell from an average of 14 mg/L at baseline to 5 mg/L after 1 year.
Clinical response (defined as a drop in the BASDAI from baseline of at least 50% or 20 mm) was achieved by 63% of the patients who had undergone BASDAI assessments.
Patients stayed on their starting TNF inhibitor regimen for a median of 4.3 years. The most common reasons for stopping treatment were lack of efficacy in 115 patients (14%) and adverse events in 69 patients (8%).
Treatment duration was shortest among women and patients with higher disease activity at the start of treatment, as measured by the BASDAI. These were the only significant predictors of treatment discontinuation in a multivariate model. Women had a 64% higher rate of stopping TNF inhibitor treatment than did men. Factors included in the model that were not significant determinants were age, C-reactive protein level at baseline, treatment with methotrexate, disease duration, and other baseline measures of disease activity.
Dr. Glintborg and her associates had no financial relationships to disclose.