Clinical Outcomes and Biologic Costs of Switching Between Tumor Necrosis Factor Inhibitors in US Veterans with Rheumatoid Arthritis

Abstract

Introduction: The purpose of this study was to evaluate clinical outcomes and drug/administration costs of treatment with tumor necrosis factor inhibitor (TNFi) agents in US veterans with rheumatoid arthritis (RA) initiating TNFi therapy. The analysis compared patients initiating and continuing a single TNFi with patients who subsequently switched to a different TNFi.

Methods: Data from patients enrolled in the Veterans Affairs Rheumatoid Arthritis (VARA) registry who initiated treatment with adalimumab, etanercept, or infliximab from 2003 to 2010 were analyzed. Outcomes included duration of therapy, Disease Activity Score based on 28 joints (DAS28), and direct drug and drug administration costs.

Results: Of 563 eligible patients, 262 initiated a single TNFi therapy, 142 restarted their initial TNFi after a ≥90-day gap in treatment (interrupted therapy), and 159 switched to a different TNFi. Patients who switched had higher mean DAS28 before starting TNFi therapy than patients with single or interrupted therapy: 5.3 vs 4.5 or 4.6, respectively. Mean duration of the first course was 34.3 months for single therapy, 18.3 months for interrupted therapy, and 17.7 months for switched therapy. Mean post-treatment DAS28 was highest for patients who switched TNFi. Mean annualized costs for first course were $13,800 for single therapy, $13,200 for interrupted therapy, and $14,200 for switched therapy; mean annualized costs for second course were $12,800 for interrupted therapy and $15,100 for switched therapy.

Conclusion: Patients who switched TNFi had higher pre-treatment DAS28 and higher overall costs than patients who received the same TNFi as either single or interrupted therapy.

Funding: This research was funded by Immunex Corp., a fully owned subsidiary of Amgen Inc., and by VA HSR&D Grant SHP 08-172.

Keywords: Adalimumab; Biologics; Cost; Etanercept; Infliximab; Rheumatoid arthritis; Rheumatology; Switching; Tumor necrosis factor; Veterans affairs.

Fig. 1

Treatment courses. Patients with RA were categorized as having undergone single therapy, interrupted therapy, or switched therapy. Patients in the single and interrupted therapy categories received one TNFi agent (“TNFi 1”) during the observation period, while patients in the switched therapy category received two TNFi agents (“TNFi 1” and “TNFi 2”) during the observation period. Patients could have undergone only a first course of treatment (i.e., the single therapy patients) or a first and second course (i.e., the interrupted and switched therapy patients); second courses of treatment began after a treatment gap 90 or more days (for interrupted therapy patients) or after initiation of a second TNFi agent (for switched therapy patients). TNFi tumor necrosis factor inhibitor, RA rheumatoid arthritis

Fig. 2

DAS28 before and during the first and second courses of treatment. Mean DAS28 values before the first course of treatment (open bars), mean values during therapy 90 or more days after the first course of treatment (light gray), and mean values during therapy 90 or more days after the initiation of the second course of treatment (dark gray) in patients receiving single therapy (left bars), interrupted therapy with the same TNFi agent (center bars), or switched therapy with a second TNFi agent (right bars) are shown. Error bars represent 95% CI. DAS28, Disease Activity Score based on 28 joints; TNFi tumor necrosis factor inhibitor, CI confidence interval