Comparison of [¹⁸F]fluorodeoxyglucose and [⁶⁸Ga]Gallium DOTA-TATE in patients with active giant cell arteritis

[¹⁸F]Fluorodeoxyglucose (FDG) is widely used in PET/CT imaging to detect large vessel vasculitis in giant cell arteritis (GCA), but its performance is suboptimal in patients receiving glucocorticoids. We aimed to compare [⁶⁸Ga]Ga-HA-DOTA-TATE, a somatostatin 2-analogue tracer, to [¹⁸F]FDG in a pilot study of patients with GCA.

Eight patients with active GCA were prospectively, sequentially scanned with both [¹⁸F]FDG PET/CT and [⁶⁸Ga]Ga-HA-DOTA-TATE PET/CT imaging. Images were evaluated by 2 blinded nuclear medicine specialists. Tracer uptake was assessed in 8 vascular territories using SUVmax, and target-background ratios (TBR) were calculated using both right atrium (TBR_RA) and liver mean (TBR_liver). Mean SUVmax and TBR of individual vascular territories and index vessels were compared.

The patient median age was 71.5 years (range 64-82), and 4 (50%) were women. Active vasculitis (≥ grade 2 visual uptake in large vessels) was present in 62.5% of [¹⁸F]FDG scans. [¹⁸F]FDG scans had higher RA background activity than [⁶⁸Ga]Ga-HA-DOTA-TATE (mean RA SUVmean 1.88 vs. 0.36, p < 0.001), while [⁶⁸Ga]Ga-HA-DOTA-TATE had a significantly higher liver uptake (mean liver SUVmean 7.54 vs. 2.39, p < 0.001). Vascular uptake (as measured by both SUVmax and TBR_liver) was significantly higher in [¹⁸F]FDG than [⁶⁸Ga]Ga-HA-DOTA-TATE scans in every vascular territory (p < = 0.05 for all comparisons), including index vessels (SUVmax 4.04 vs. 1.91, p = 0.01, TBR_liver 1.73 vs. 0.27, p < 0.001).

In this pilot study of patients with active GCA, the arterial uptake of [⁶⁸Ga]Ga-HA-DOTA-TATE was lower and less conspicuous compared to [¹⁸F]FDG. While further evaluation in larger cohorts is needed, a clear advantage of [⁶⁸Ga]Ga-HA-DOTA-TATE over [¹⁸F]FDG for detecting vascular inflammation in GCA was not identified. TRIAL REGISTRATION, CLINICALTRIALS.GOV: NCT03812302, registered 2019-01-18, URL: https://clinicaltrials.gov/search?cond=dotatate%20%26;term=giant%20cell%20arteritis .