Drug survival of the first course of anti-TNF agents in patients with rheumatoid arthritis and seronegative spondyloarthritis: analysis from the MonitorNet database

Objective To compare drug survival of different anti-TNF drugs (infliximab, INF, etanercept, ETA, and adalimumab, ADA) in rheumatoid arthritis (RA) and spondyloarthritis (SpA) by analysing data collected from an Italian multicentre observational cohort study. Methods All patients with RA or SpA registered in the MonitorNet database who started their first course of anti-TNF therapy were included. Overall drug survival was measured, along with specific reasons of discontinuation (inefficacy or adverse events). A first set of analyses using RA as reference category assessed the relationship between diagnosis and drug survival. A second set of analyses stratified by diagnosis (RA and SpA) used INF as reference drug. Adjustment for confounders was performed. The results are presented as adjusted hazard ratios (adjHR) and 95% confidence intervals (95%CI). Results 2640 RA patients and 1220 SpA patients with a median follow-up of 17 months (IQR 7.2-33.4) were included in the analyses. Patients with a diagnosis of SpA showed a lower risk of drug discontinuation with an adjHR (95%CI) of 0.81 (0.73, 0.90). In SpA, the subset of patients with ankylosing spondylitis (AS) showed the best survival on treatment. In RA, both ETA and ADA showed a significantly lower probability of withdrawal when compared to INF [adjHR (95%CI) 0.46 (0.38, 0.56) and 0.68 (0.57, 0.81), respectively]. Similar results were found in SpA. Conclusion Drug survival for SpA is longer than that in RA mainly due to the AS subgroup. In both RA and SpA, ETA and ADA showed a better retention on treatment when compared to INF.