Abstract: Background: Tocilizumab (TCZ) is currently the first biological drug approved for the treatment of giant cell arteritis (GCA), regardless of disease stage or phenotype. The window of opportunity, a critical period for early intervention, is increasingly recognized in immune-mediated inflammatory disorders (IMIDs).
Objectives: To assess whether there was a window of opportunity at the classic cut-off point used in clinical trials (e.g., GiACTA).
Patients and methods: Multicenter observational study of 471 patients with GCA treated with TCZ. Patients were stratified into two groups: Newly Diagnosed (TCZ ?6 weeks from diagnosis) and Refractory (>6 weeks). Timing effects were assessed using multivariable regression models adjusted for potential confounding factors, evaluating both the dichotomous variable "newly diagnosed GCA" and the continuous variable "time from GCA diagnosis to TCZ initiation"; multiple time cut-offs were also analyzed following the same methodological approach.
Results: Of the 471 patients (72.6 % female; mean age 73.5 ± 9 years), 91 (19.3 %) were classified as newly diagnosed and 380 (80.7 %) as refractory. No significant differences were observed in EULAR-defined remission, cumulative organic damage, or relapse rates after 24 months of TCZ. Using the continuous variable "time from GCA diagnosis to TCZ initiation", a significant association was observed between shorter time to TCZ initiation and EULAR remission at 24 months (OR 0.983; 95 % CI 0.967-0.999; p = 0.035), whereas no significant associations were found for organ damage or relapses.
Conclusions: Although no clear window of opportunity was identified using the classic cut-off for TCZ initiation in GCA (?6 weeks), an earlier initiation of TCZ after diagnosis appears to be associated with a higher likelihood of remission in patients with GCA.
