SAN DIEGO, CA—More than 80% of patients with psoriatic arthritis treated with infliximab in clinical practice received sustained treatment with doses less than the 5mg/kg every eighth week recommended in international guidelines; however, a low infliximab starting dose had no effect on drug survival or treatment responses, a registry study reported at the 2013 ACR/ARHP Annual Meeting.
In fact, a low starting dose with gradual dose escalation “was a preferred and effective strategy,” noted Bjorn Gudbjornsson, PhD, of the Center for Rheumatology Research (ICEBIO), Landspitali – The National University Hospital of Iceland, Reykjavik, Iceland, and colleagues.
Noting that data on use of lower doses in this population is scarce, the investigators conducted an observation cohort study based on the nationwide Danish DANBIO and Icelandic ICEBIO registries to describe dose regimens, frequency of dose escalation, and outcomes in patients with psoriatic arthritis routinely treated with infliximab.
Demographic and baseline characteristics were identified among patients who were tumor necrosis factor-α inhibitor (TNFi)-naïve and treated with ≤3 mg infliximab/kg, 3–5mg/kg, or ≥5mg/kg with treatment scheduled at 0, 2, 6, and then every eighth week. Dose escalation was defined as an increase in either dose and/or frequency.
Treatment responses were evaluated by ACR20/50/70 and EULAR-good-response after 6 months of treatment and disease activity after 1 year of treatment. Kaplan-Meier plots and regression analyses were performed for drug survival analyses and to identify predictors of treatment response and drug survival.
Among the 1589 patients identified in the registries, 462 (29%; 376 Danish and 86 Icelandic) were treated with infliximab. The starting infliximab dose was ≤3mg/kg in 174 patients (38%), 3–5mg/kg in 174 (38%), ≥5mg/kg in 38 (8%) and not specified in 76 (16%). After 1 year, corresponding percentages were 35%, 53%, 12%, and 22%, respectively.
Patients with higher body weight received lower infliximab doses per kg. Median time until first dose escalation, 273 days (interquartile range, IQR 153–553), was independent of the starting dose (log rank 0.1; P=0.9). The ACR20/50/70 or EULAR-response rates, drug survival (P=0.09), and 1-year disease activity were also independent of baseline dose. Icelandic patients received lower infliximab doses (2.3mg/kg [2.1–2.9]) than Danish patients (3.1mg/kg [3.0–3.8]; median [IQR], P<0.05) and also had longer drug survival (1183 vs. 483 days); however, 1-year response rates were similar.