AB0474 Comparison of drug retention rates between anti-tumor necrosis factor agents in rheumatoid arthritis and ankylosing spondylitis in daily clinical practice

Background The efficacy of different anti-tumor necrosis factor alpha (anti-TNF) agents in rheumatoid arthritis (RA) and ankylosing spondylitis (AS) has not been directly compared in clinical trials, and meta-analysis showed no differences between them1,2. Drug retention rates obtained in observational studies are indicators of treatment success3. Objectives To analyze the retention rates and causes of discontinuation among anti-TNF agents in our local cohort of RA and AS patients. Methods We conducted an observational prospective study. Patients treated with infliximab (INF), etanercept (ETN) and adalimumab (ADA) since January 2001 to November 2011 were included. The causes of discontinuation were categorized as: inefficacy, adverse events, clinical remission and loss of follow up. Kaplan-Meier survival function was estimated. Factors that could determine the time to discontinuation were analyzed using a Cox proportional hazard ratio model. Results A total of 318 treatments were started: 97 INF, 105 ETN and 116 ADA. Total exposure to TNF inhibitors was 589 patient-years. Discontinuations due to adverse events were: 49% INF, 34% ADA and 33% ETN. ETN retention curves were higher than INF or ADA. Cox regression analysis showed higher risk of discontinuation for INF than ETN (Table 1) in both RA and AS patients, but comparison between ETN and ADA do not showed statistical differences. Table 1. Cox regression RA (n=152)AS (n=109) HRCI 95%HRCI 95% Etanercept11 Adalimumab1,58(0,92-2,73)1,71(0,69-4,25) Infliximab2,68*(1,43-5,02)2,88**(1,47-5,63) Adjusted by age, gender, mantoux, time from diagnosis. *p