Possible predictors for relapse from etanercept discontinuation in ankylosing spondylitis patients in remission: a three years’ following-up study

The aim of this study is to assess the recurrence probability and the possible predictors in patients with ankylosing spondylitis from etanercept discontinuation in a 3-year observational cohort (ClinicalTrials.gov: NCT02915354). A cohort of 35 patients who achieved an ASAS 20 response at the end of a randomized controlled trial underwent a 3-year follow-up evaluation. The primary end point was clinical relapse defined as the BASDAI score going back to 80% of its initial level at the beginning of the trial. Prognostic factors of relapse were analyzed using the Cox regression. Median duration of clinical remission was 15.0 months (interquartile range, 3.7–26.3 months). The cumulative probabilities of relapse at 1, 2, and 3 years were 45.7, 57.1, and 60.0%, respectively. The proportion of recurrence was not significantly different between placebo group and etanercept group by Kaplan-Meier analysis (placebo vs. etanercept: 61.11 vs. 58.82%, P = 0.890). Two independent factors associated with increasing risk of relapse were (1) age of patients (25 years or older with risk of 3.07, 95% confidence interval, 1.19–7.97, P = 0.021); (2) onset age (younger than 24 years with risk of 3.12, 95% confidence interval, 1.24–7.83, P = 0.016). No correlation was observed in the present study between the time of relapse and the duration of the treatment with etanercept in AS patients who achieved the ASAS 20 response after receiving the treatment. The older age and younger onset age of patients seems to be important factors associate with an increasing risk of relapse.