Use of Gallium-68 HA-DOTATATE PET/CT in Giant Cell Arteritis (GCA)

Phase 2

Completed

Brief Summary: The aim of this study is to compare the use of FDG PET/CT to Ga-68 HA-DOTATATE (abbreviated DOTATATE) PET/CT in patients with active giant cell arteritis (GCA) started on prednisone to understand if DOTATATE can identify more areas of active blood vessel inflammation than FDG.

Detailed Description: The aim of this study is to prospectively evaluate the potential use of 68-Ga HA-DOTATATE PET/CT for detecting medium-large vessel inflammation in a small number of GCA patients with active disease, as compared to FDG PET/CT, and to understand if DOTATATE uptake correlates with disease activity. Fifteen patients with active GCA (either newly-diagnosed or recently relapsed disease) who are receiving glucocorticoids will be enrolled. Participants will undergo baseline FDG PET/CT and baseline DOTATATE PET/CT scan. Tracer uptake will be described in 8 major vascular territories. DOTATATE PET/CT will be repeated again in 6 months, and tracer uptake will be correlated to clinical disease activity, and medication use.

Recruitment & Eligibility

Inclusion Criteria

Participants must:

Meet the revised GCA diagnosis criteria (modified from ref 1)
Have either newly-diagnosed or relapsing disease
Have active disease (modified from ref 1, to remove ESR/CRP requirements)
Have been empirically started on glucocorticoid treatment (or had baseline glucocorticoid dose increased, in the case of relapsers) ≤ 2 weeks of enrolment
Participant must be have had (or will be willing to undergo) an urgent FDG-PET/CT as part of routine clinical care.

GCA diagnosis criteria (modified from ref 1, to remove ESR requirement).

Age ≥ 50 years
And at least 1 of a. or b. :
1. Unequivocal cranial symptoms of GCA (new headache, scalp or temporal artery tenderness, ischemia-related vision loss, jaw/mouth claudication
2. Unequivocal symptoms of polymyalgia rheumatica (PMR), defined as shoulder and/or hip girdle pain associated with inflammatory stiffness
And at least 1 of a. or b.:
1. Temporal artery biopsy revealing features of GCA
2. Evidence of large-vessel vasculitis by angiography or cross-sectional imaging study such as magnetic resonance angiography (MRA), computed tomography angiography (CTA), or positron emission tomography-computed tomography (PET-CT)

Arm && Interventions

Group	Intervention	Description
DOTATATE	68-Ga HA-DOTATATE PET/CT	All 15 GCA patients will undergo 68-Ga HA-DOTATATE PET/CT imaging at baseline, in addition to FDG PET/CTA (as part of standard of care). DOTATATE PET/CT imaging will be repeated at 6 months follow-up.

Primary Outcome Measures

Name	Time	Method
Comparison of FDG vs DOTATATE vascular uptake in individual vascular territories using target-blood pool ratios (TBR)	time 0 (baseline)

Secondary Outcome Measures

Name	Time	Method
Qualitative comparison of FDG vs DOTATATE vascular uptake in individual vascular (scores 0-3) territories using visual uptake scores	time 0 (baseline)
Correlation between vascular DOTATATE uptake scores and clinical status	0 and 6 months
Changes in vascular DOTATATE uptake scores over time (quantitatively and qualitatively)	6 months
Correlation between vascular DOTATATE uptake scores and cumulative glucocorticoid exposure	0 and 6 months