This study examined the proportion and magnitude of dose escalation nationally and regionally among rheumatoid arthritis (RA) patients treated with TNF-blockers and estimated the costs of TNF-blocker therapy.
This retrospective cohort study used claims data from US commercially-insured adult RA patients who initiated adalimumab, etanercept, or infliximab therapy between 2005-2009. Biologic-naïve patients enrolled in the health plan for ≥6 months before and ≥12 months after therapy initiation were followed for 12 months. Dose escalation was assessed using three methods: (1) average weekly dose > recommended label dose, (2) average ending dispensed dose > maintenance dose, and (3) average dose after maintenance dose > maintenance dose. Annual cost of therapy included costs for mean dose and drug administration fees.
Overall, 1420 etanercept, 874 adalimumab, and 454 infliximab patients were included. A significantly lower proportion of etanercept-treated patients had dose escalation using the average weekly dose (3.9% vs 21.4% adalimumab and 69.6% infliximab; p < 0.0001), average ending dispensed dose (1.1% vs 10.6% adalimumab and 63.0% infliximab; p < 0.0001), and average dose after maintenance dose methods (2.8% vs 15.7% adalimumab and 69.6% infliximab; p < 0.0001). Regional dose escalation rates and magnitudes of escalation were directionally consistent with national rates. Etanercept had the lowest cost per treated RA patient ($19,690) compared to adalimumab ($23,020) and infliximab ($24,030).
Exclusion of patients not on continuous TNF-blocker therapy limits the generalizability; however, ∼50% of patients were persistent on therapy for 12 months. The study population comprised RA patients in commercial health plans, thus the results may not be generalizable to Medicare or uninsured populations.
In this retrospective study, etanercept patients had the lowest proportions and magnitudes of dose escalation across all methods compared to adalimumab and infliximab patients nationally and regionally. Mean annual cost was lowest for etanercept-treated patients.