Difficult-to-treat rheumatoid arthritis among elderly patients from the KOBIO registry.

Background: 'Difficult-to-treat (D2T)' rheumatoid arthritis (RA) refers to patients who fail to achieve low disease activity or remission despite multiple biologic or targeted synthetic disease modifying anti-rheumatic drugs (b/tsDMARD) cycles. Elderly RA patients often have higher disease activity and more comorbidities. This study aimed to determine the prevalence of D2T-RA in elderly RA patients treated with b/tsDMARDs and examine their characteristics and treatment outcomes.

Methods: Data were extracted from the Korean College of Rheumatology Biologics registry for RA patients receiving b/tsDMARDs.

Results: Among 516 elderly RA patients (≥65 years) on b/tsDMARDs, 54 (10.5 %) had D2T-RA. Younger age (OR = 0.905, p = 0.012), higher RAPID3 scores (OR = 1.082, p = 0.044), lack of prior leflunomide use (OR = 0.446, p = 0.009), and lack of prior use of two or more conventional synthetic DMARDs (csDMARDs) (OR = 0.114, p < 0.001) were associated with D2T-RA. Drug survival rates were similar between D2T-RA and non-D2T-RA groups (p = 0.53). Discontinuation and switching rates did not differ, but inefficacy was a more frequent withdrawal reason in D2T-RA (63 % vs. 29.7 %, p = 0.001). Disease activity scores remained higher in D2T-RA patients at 1- and 2-year follow-ups.

Conclusions: Among elderly RA patients on b/tsDMARDs, 10.5 % had D2T-RA. Younger age, higher RAPID3, absence of prior leflunomide use, and absence of prior use of two or more csDMARDs were associated with D2T-RA. Despite comparable drug survival, persistent disease activity underscores the need for ongoing efficacy evaluation and tailored treatment strategies for better disease control.