The recent analysis of data included in the Stockholm TNFα Follow- Up (STURE) registry showed that the concomitant use of methotrexate (MTX) with etanercept (ETN), adalimumab or infliximab was associated with long-term drug survival of anti-tumour necrosis factor (TNF) agents in patients with psoriatic arthritis (PsA).1 The positive effect of MTX was primarily linked to fewer drop-outs due to adverse events.1 This analysis did not consider each anti-TNF drug subgroup. For this reason we determined the cumulative probability of taking ETN with or without MTX in a large cohort of patients.

We prospectively studied 82 patients, admitted to our rheumatological unit since 2001, affected by PsA, classified according to Moll and Wright criteria, modified by Helliwell et al,2 treated with ETN alone or in combination with MTX. The main clinical demographic features of each patient were recorded, including the pattern of articular involvement. Clinical assessment was performed according to the Psoriatic Arthritis Response criteria.3 Axial response was evaluated by the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI).4 The withdrawals from treatment were registered and classified as adverse events or lack of response.

The main demographic and clinical features, including the rate of withdrawals due to inefficacy or toxicity, were not significantly different in patients with PsA treated with ETN (25 mg/twice a week) alone or in combination with MTX (10–15 mg/weekly) (table 1). Kaplan–Meier life-tables for the ETN group vs the group ETN+MTX are shown in fig.1. A log rank test to compare survival curves showed that the probability curve of taking ETN alone was not significantly different from that of ETN+MTX. These results did not confirm the previous results of Kristensen et al,1 who reported a positive effect of concomitant MTX primarily associated to the decreased risk of treatment cessation due to any adverse events. Nevertheless, in these studies the treatment is not allocated randomly, and it could be related to disease activity or to previous MTX toxicity. With respect to this last condition, the ETN group could include patients with a higher probability to develop drug adverse events. Moreover these results may have been affected by the notable proportion of patients with PsA treated with infliximab (almost 40%) in this study.1 Indeed, infliximab is recommended in conjunction with MTX for patients with rheumatoid arthritis (RA), because the combination is associated with a reduction in the development of human antichimeric antibodies and longer duration of the benefits of the drug as compared to monotherapy.5 6

• Download figure
• Open in new tab
• Download powerpoint

Figure 1 Kaplan–Meier life table for etanercept (ETN) group (n = 51) vs the groups ETN+methotrexate (MTX) (n = 31) in patients with psoriatic arthritis (PsA). Withdrawal was due to: any reason (A), failure to adhere to treatment (B), adverse events (C).

However, in the PsA studies of all three anti-TNF agents, the concomitant stable use of MTX was allowed (but was not an inclusion criterion) and actually occurred in about half of the patients. It did not seem to affect any of the clinical or radiographic responses.7 8 In particular, results do not deny synergy between the two drugs in PsA as there is in RA9 10 but further studies on de novo initiation of ETN and ETN+ MTX are required.

In conclusion, ETN can be used either in monotherapy or in combination with MTX, but concomitant MTX treatment does not seem to be a positive predictor of anti-TNF drug survival in the treatment of patients with PsA.