How Often does Follow up 18F-FDG PET/ct Improve or Become Inactive in Patients with Active Large Vessel-Giant Cell Arteritis (LV-GCA) After Escalating Treatment: A Systematic Review

Objectives Biomarkers that correlate with clinical disease activity are greatly needed in giant cell arteritis (GCA), particularly for patients with large vessel vasculitis (LVV) and those receiving tocilizumab (TCZ.). We performed an updated systematic review to determine (1) how often does vascular uptake on FDG PET/CT improve or (2) become inactive in patients with large vessel GCA (LV-GCA) who clinically improve after escalating treatment.

Methods MEDLINE, EMBASE, CINAHL, Scopus, and Cochrane Library were searched from inception through February 29, 2024. Full text longitudinal studies were included if they: described a minimum of 2 patients with active LV-GCA on baseline PET, and the results of follow up PET scan done ≥ 3 months after escalating immunosuppression, along with an assessment of clinical disease activity. Two reviewers independently performed screening, full text review and data collection, and assessment of study quality using the Quality Assessment of Diagnostic Studies-2 (QUADAS-2).[1]

Results 3131 unique references were screened, of which 25 studies were included (7 prospective, 18 retrospective), describing 377 patients with GCA. Mean patient age was 70.2 years (±5.4 yrs) and 72% were women. In 24 (96%) studies, patients received glucocorticoids, and in 10 studies (40%) tocilizumab was added. Patients underwent an average of 2.3 PET scans, at mean 9.2 ±5 months apart. An assessment of both clinical disease activity and follow up PET in comparison to baseline results (improved/not improved) was available for 158 LV-GCA patients. Overall, vascular FDG uptake improved on follow up PET in 122/149 (82%) patients who clinically improved with treatment. In the 62 patients who received TCZ, follow up PET improved in 100%. In the 9 patients without clinical improvement, none (0%) had radiographic improvement on repeat PET. In 283 patients with LV-GCA, baseline and follow up PET scans were reported as either still active or inactive. Ultimately, follow up PET became inactive in 119 of 254 patients (47%) who entered clinical remission on treatment. Among the 29 patients who remained clinically active, PET became inactive in 3 (10%). In the TCZ-treated patients, follow up PET became inactive in 76/112 patients (68%) in clinical remission, and remained radiographically active in 6/6 (100%) who remained clinically active.

Conclusion Vascular FDG uptake on follow up PET improved in most (>80%) patients with LV- GCA patients who clinically improved on treatment but ultimately became radiographically- inactive in fewer than half (47%.) Follow up scans improved (100%) and became inactive (68%) more often in TCZ-treated patients.

References [1.] Whiting PF. Ann Intern Med 2011;155:529-36.