Background Since 2004, Korean national health insurance began to cover the cost of biologic agents in rheumatoid arthritis (RA) patients experiencing treatment failure by conventional disease modifying antirheumatic agents. However, real-world issues such as selecting or switching among biologic agents in clinical practice became more complicated as types of the agents increased.
Objectives To evaluate 1) first choice among biologic agents, 2) drug retention rate and duration and 3) switching rate and duration before switching of each biologic agent in RA.
Methods We used prospective cohort data by the National Health Insurance Service (NHIS) in Korea, which consisted of more than one million subjects representing age, sex and income status of whole Korean population followed from 2004 to 2013. All RA patients with any experience of biologic agents were checked by the code of each drug and KCD9 code of diagnosis including all types of RA. To supplement the results of the population based study, we also compared and validated with the independent cohort of biologic agent users in Seoul national university hospital (SNUH).
Results One hundred and seventy three patients were found to experience any of TNFa inhibitors from Jan. 2004 to Dec. 2013. Etanercept was the most frequent choice as first TNFa inhibitor (43.4%), followed by adalimumab (35.3%), infliximab (20.2%), golimumab (0.6%) and abatacept (0.6%). Among TNFa inhibitors, retention rates of etanercept (73.1%, 62.7%) at month 12 and 24 were significantly higher (p=0.039, both) than adalimumab (57.7%, 44.2%) and infliximab (45.5%, 36.4%). In SNUH cohort, etanercept (79.8%, 67.0%) also had better retention rate than adalimumab (51.3%, 48.7%) and infliximab (58.6%, 34.5%) at month 12 and 24 respectively. Mean duration of retention was almost twice longer in etanercept (3.42 years) than adalimumab (1.83 years, p=0.004) and infliximab (1.71 years, p=0.011). Similarly, etanercept (3.24 years) prescribed longer than adalimumab (1.98 years) and infliximab (1.63 years) with statistical significance in SNUH cohort. Etanercept also had lower switching rate (20.9%) than adalimumab (32.1%) and infliximab (38.5%, p=0.040) and the tendency were similar in SNUH cohort. Preferred biologic agents after switching were adalimumab (27.4%) and rituximab (24.2%). Etanercept users (1.35 years) had longer duration of use before switching than infliximab (0.60 years, p=0.050) but no significant difference was shown comparing with adalimumab (0.73years, p=0.483).
Conclusions As golimumab, abatacept, tocilizumab were available relatively later than existing TNFa inhibitors and rituximab, more follow up period would be required to evaluate their value in treating RA. This research can be a pilot study before analyzing nationwide population cohort encompassing whole population of Korea. Conclusively, etanercept has been prescribed longer in general and the rate of retention till 2 years was also better then adalimumab and infliximab for 10 years after national insurance coverage.
Disclosure of Interest None declared