Background Dose reduction of etanercept after clinical remission in patients with ankylosing spondylitis (AS) is not uncommon practice. However, efficacy and optimal schedule of dose tapering is rarely evaluated.
Objectives To investigate the efficacy and safety of low dose etanercept treatment (25mg or less/week) after clinical remission of AS in real world.
Methods In this study, 134 AS patients who treated with etanercept for at least 12 months and achieved clinical remission (BASDAI <4 and normal C-reactive protein level) between 2004 and 2013 were enrolled. Dose reduction was performed in 100 patients (low dose group) after achieving clinical remission based on physician's medical decision. Other 34 patients (standard dose group) maintained the dosage of 50mg/week until discontinuation. Drug survival (time to drug discontinuation due to inefficacy or adverse event) and incidence of significant adverse events were compared between two groups. In patients with low dose group, clinical factors and time to dose reduction associated with longer drug survival were estimated.
Results Clinical and demographic features were comparable between two groups at the time of starting etanercept except for age (43.4 years in low dose group vs. 52.0 years in standard dose group, p=0.001). In low dose group, median time to dose reduction was 19.5 (10.1-39.6) weeks. During 536.8 person-years (PYs) of follow up, 27 patients stopped etanercept (21/440.9PYs in low dose group and 6/95.9PYs in standard dose group). Crude drug survival of low dose group was not significantly different from that of standard group (98.0% vs. 93.5% at 2 years, 92.1% vs. 89.4% at 3 years and 84.4% vs. 76.2% at 4 years). This finding was consistent after adjustment of clinical factors including age, gender, disease duration, initial BASDAI, concomitant MTX and previous TNF-blocker use (adjusted HR=0.552, 95% C.I. 0.208-1.465) (Figure). Incidence of adverse events which led to discontinuation of etanercept also showed no difference between two groups (40.82/1000PYs in low dose group vs. 52.16/1000PYs in standard dose group, p=0.783). In the subgroup analysis with low dose group, dose reduction after more than 24 weeks of standard dose treatment was significantly associated with longer drug survival after adjustment of other clinical factors (adjusted HR 0.273, 95% C.I. 0.085-0.875).
Conclusions In patients with AS who achieved clinical remission, low dose etanercept treatment showed comparable long-term efficacy and safety in real world. Among various strategies of dose reduction, more than 24 weeks of standard dose treatment before adjustment was associated with longer drug survival.
Disclosure of Interest None declared
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