0536: Can achieving sustained low disease activity through treat-to-target management arrest enthesiophyte progression in psoriatic arthritis? A two-year prospective study using high resolution peripheral quantitative computed tomography

Background/Purpose: Enthesitis is a hallmark feature of psoriatic arthritis (PsA). Chronic inflammation in the entheses can lead to the formation of enthesiophytes (bony spurs), and this new bone formation may result in functional loss over time. Although substantial improvements in clinical response has been observed using the treat-to-target (T2T) management strategy, limited studies have demonstrated its effect on radiographic outcomes, particularly regarding new bone formation. Therefore, the objective of this study was to ascertain the effect of achieving Sustained Disease Activity in PSoriatic Arthritis (DAPSA) low disease activity (LDA) on the progression of enthesiophyte in MCP2-4 using HR-pQCT.

Methods: One hundred consecutive PsA patients were recruited to this 2-year prospective study. They received protocolized T2T treatment aiming at DAPSA-LDA. Sustained DAPSA-LDA (SDL) was defined as achievement of DAPSA-LDA at month 12, 18 and 24. HR-pQCT of the MCP2-4 were performed at baseline, one and two years,. Enthesiophytes were defined as new bone formation arising from the periosteal bone cortex at the insertion sites of the capsule, ligament, or tendons or at the location of functional enthesis.(1) Enthesiopyte volume was quantified were quantified semi-automatically. Progression of pre-existing enthesiophyte were defined as increase in enthesiophyte volume exceeding least significant change (LSC, 1.1mm³).

Results: Ninety-five patients (age: 51±14 years, 57 (60%) male, disease duration: 3.9±6.1 years) who completed 2-year follow-up were included. After 2-years of T2T management, a significant decrease in disease activity (DAPSA - baseline: 25.1±12.7 vs Year 2: 8.4±6.8, p< 0.001) were observed, and 59 (62.1%) patients achieved SDL. The use of biologic disease modifying anti-rheumatic drug (bDMARDs) increased from 5% at baseline to 64% at year 2. Regarding enthesiophyte, a total of 64 and 47 enthesiophytes were identified at baseline for patients in SDL and non-SDL group respectively. After 2 years, enthesiophyte volume in non-SDL group progressed [median (IQR) of change: 0.77mm³ (-0.19, 2.22)] and that in SDL group remained stable [median (IQR) of change: 0.08 mm³ (-0.61, 0.73), p=0.035]. Enthesiophyte volume progression was significantly higher in non-SDL group (40% vs 19% in SDL group, (p=0.031). Using generalized estimating equation (GEE), after accounting for within subject variance, achieving SDL protected against enthesiophyte volume progression (OR=0.35, 95% CI: 0.14-0.88, p=0.025), independent of age, sex, disease duration and bDMARDs use.

Conclusion: Achievement of sustained disease activity control protects against progression of enthesiophyte in PsA.