Background/Purpose

Methotrexate (MTX) is used as first-line treatment in psoriatic arthritis (PsA); however, the extent of the disease-modifying effect of MTX on PsA, if any, is not established. Randomized controlled trials examining the efficacy of MTX have been either under-powered or have used dosages that may be sub-optimal. While TNF inhibitors (TNFi) are used as second-line therapies in PsA, they have proven efficacy and disease-modifying effect. Minimal disease activity (MDA) is achieved at 24 weeks in 39% and 52% of patients treated with adalimumab and infliximab, respectively. There is a need to establish the treatment effect of MTX. An international task force recently recommended that disease remission or MDA be the target of treatment and should be attained within 6 months of initiating medication.

The aims of this retrospective study were to: a) establish the percentage of PsA patients that achieve MDA after 6 months of treatment with MTX, and b) identify the dose of MTX most likely to achieve MDA.

Methods

All patients attending a large, tertiary referral centre for PsA who initiated MTX and were naïve to biological medication on or after January 2004 up until April 2014 were assessed for inclusion. The primary outcome was the achievement of MDA after 6 months of MTX. MDA is defined as: the presence of at least 5 out of the following 7 domains: tender joint count ≤ 1, swollen joint count (SJC) ≤ 1, Psoriasis Area Severity Index (PASI) ≤ 1 or body surface area ≤ 3%, tender entheseal points ≤ 1, Health Assessment Questionnaire score ≤ 0.5, patient global disease activity Visual Analogue Scale (VAS) score ≤ 20 and patient pain VAS ≤ 15.

Of 204 patients identified, 29 had insufficient duration on MTX to accurately assess outcome. These were excluded, leaving 175 for analysis. Of these, 167 patients had sufficient data for analysis at 6 months.

Results

Of 204 patients, 54% were male. At the start of MTX use (all mean (SD)), age was 47.1 (13.5) years, duration of PsA 6.2 (8.0) years, PASI 5.5 (8.0), tender joint count 10.2 (10.7) and swollen joints 6.0 (7.4). Oral MTX was prescribed in 77.5%; 22 (10.8%) had been prescribed a DMARD in the past.

After 6 months on MTX, 29 patients (17.4%) achieved MDA, despite 97 patients (58.1%) achieving a SJC ≤ 1 and 138 (82.6%) a PASI ≤ 1; Patient-reported outcomes were less responsive, with only 22 (13.2%) achieving the outcome for disease activity. For patients achieving MDA, mean dose was 17.8 (4.2) mg/week by 6 months, with 58.6% taking ≥ 17.5 mg/week (76% were taking oral MTX). This dose was similar in those not achieving MDA. Back pain (both inflammatory and mechanical) and dactylitis were associated with a lower probability of achieving MDA.

Conclusion

Based on this analysis, MTX use achieves the recommended treatment target of MDA by 6 months in less than 20% of patients. This low rate of achievement is explained by failure of response in the patient-reported outcome components of the MDA criteria. Adequately-powered randomized controlled trials are needed to establish the efficacy of MTX as a first line drug in PsA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/attainment-of-minimal-disease-activity-using-methotrexate-in-psoriatic-arthritis/