An increase in the number of joints affected by psoriatic arthritis doesn't usually lead to changes in TNF blocker treatment, this retrospective study shows. But changes in discontinuation over time and by gender are puzzling.
Iannone F, Lopriore S, Bucci R, et al., Two-year survival rates of anti-TNF-Î± therapy in psoriatic arthritis (PsA) patients with either polyarticular or oligoarticular PsA. Scand J Rheumatol. 2015;44:1-8
A majority of patients with psoriatic arthritis (PsA) keep on taking their first tumor necrosis factor alpha (TNFÎ±) blocker for up to 2 years. Overall “drug survival” is not significantly different between patients with poly-articular or oligo-articular forms of the disease, say these Italian researchers.
The longitudinal registry study of 328 PsA patients prescribed their first TNFÎ± blocker at outpatient rheumatology clinics-etanercept (Enbrel), adalimumab (Humira), or infliximab (Remicade)-was designed to assess whether discontinuation of these drugs increases as disease (presumably) progresses from one to many joints.
In the study, the poly-PsA subgroup is defined by involvement of 5 or more joints and higher disease activity scores in 28 joints (DAS28>3.2).
Etanercept had better continuation rates compared to infliximab and adalimumab among 213 poly-PsA patients (68.3%, 58.2%, and 51.9%, respectively). But there were no major differences among the 115 oligo-PsA patients, suggesting that TNF drugs may perform differently in different patient subgroups.
Among oligo-PsA patients, etanercept had the best continuation rates (79.2%), but the differences between theother two TNF blockers were not statistically significant (70.9% for etanercept and 62.2% for adalimumab).
Overall, around a third of the patients discontinued treatment after 2 years during the follow-up period between 2003 and 2011.
Interestingly, drug continuation rates differed between two specific time periods, 2003-2008 and 2009-2011. More than 76% of the 213 poly-PsA patients stayed on TNF therapy during the earlier period, but only 51.1% in the later period. The reasons for this are unclear, as there were no obvious differences in outcomes or adverse events. But the authors note a trend toward greater drug discontinuation rates in recent years.
They also observe that female gender was a positive predictor of discontinuation among oligo-PsA patients. More than half (61%) of these subjects were women in their late 40s. Women were more likely to have quit therapy during the earlier time period but the reasons for this are also unclear.
Clinical responses, a secondary outcome, differed somewhat between the groups. 'Good' responses, in terms of European League Against Rheumatism (EULAR) criteria, were more frequent for etanercept or infliximab among the poly-PSA patients after 12 months. But after 2 years there were no differences in disease activity (DAS28<2.6) or in functional disability in this group.
Among patients with oligo-PsA,more achieved a EULAR good response with infliximab and DAS28 remission with infliximab or etanercept.
Larger studies that allow for more accurate analysis of subgroups could help to improve disease management, the authors say.