Objective: To determine whether previous findings of dose escalation with infliximab versus abatacept were reproducible in claims data using a larger sample size and longer follow-up.
Method: Claims-based analysis of commercial enrollees of a large, US-managed care plan was conducted to examine treatment patterns among adult patients with RA. The identification period was January 1, 2006 through August 31, 2010. Patients newly initiated on infliximab or abatacept who had at least five infusions were included. Patients with evidence of other indications for biologic treatment (e.g. psoriasis) were excluded. Continuous plan enrollment for 6 months before initiation through the fifth infusion was required. Patients were followed until plan disenrollment, treatment termination, or August 31, 2010. Dose escalation was defined as two or more increases in either dose amount or frequency following the third infusion.
Result: A total of 1198 patients initiating infliximab and 799 patients initiating abatacept were identified, with a mean follow-up time of 477 and 275 days, respectively. The average increase in number of infused vials between the first and last infusion was 1.30 for the infliximab cohort and 0.12 for the abatacept cohort (p<0.001). The proportion of infliximab patients who experienced dose escalation during the follow-up period was 70.7%, with 56.6% having an increase in dose amount and 51.9% having an increase in frequency. In contrast, only 11.3% of the abatacept cohort experienced escalation, with 10.5% having an increase in dose amount and 1.1% having an increase in frequency (p<0.001 for all comparisons). On average, time to first dose escalation did not differ between the two treatment groups (143.4 vs 149.0 days; p=0.68). Risk of escalation remained substantially lower for abatacept patients after controlling for patients’ demographic and clinical characteristics in a multivariate survival model (hazard ratio=0.115; p<0.001).
Conclusion: The majority of patients treated with infliximab experienced dose escalation, whereas significantly fewer patients treated with abatacept had evidence of escalation. Furthermore, the escalation in dose seen with abatacept was relatively minor compared with that observed with infliximab and was consistent with previous analyses1.
1. Darkow T, et al. Comparison of Dose Escalation among Rheumatoid Arthritis Patients Treated with Infliximab or Abatacept. AMCP 2010 Educational Conference, Oct. 13-15, 2010, St. Louis, MO.
Disclosure: T. Darkow, Bristol-Myers Squibb, 1, Bristol-Myers Squibb, 3 ; B. Chastek, i3 Innovus, 1, i3 Innovus, 3 ; L. Rosenblatt, Bristol-Myers Squibb, 1, Bristol-Myers Squibb, 3 ; D. Trivedi, Bristol-Myers Squibb, 1, Bristol-Myers Squibb, 3 ; T. Hebden, Bristol-Myers Squibb, 1, Bristol-Myers Squibb, 3 ; H. Henk, None; F. Liu, i3 Innovus, 1, i3 Innovus, 3 .