Simplifying PET imaging for cardiac sarcoidosis: a prospective comparison of 64Cu DOTATATE and 18F FDG
A Yafasova, E Fosboel, N Noory, P Hasbak, K Rossing, J Butt, J Jensen, H Johannesen, L Koeber, A Kjaer, F Gustafsson, R RipaAbstract
Background
Cardiac sarcoidosis is a potentially life-threatening condition. Diagnosis is challenging and relies on multimodal imaging, including 18F-FDG positron emission tomography/computed tomography (PET/CT). 18F-FDG PET/CT is complicated by high physiological myocardial 18F-FDG uptake, requiring extensive patient preparation with dietary restrictions and fasting. A potential alternative to 18F-FDG is 64Cu-DOTATATE, a clinically safe radiotracer which targets somatostatin receptors on inflammatory cells in sarcoid granulomas without binding to normal cardiomyocytes or requiring any patient preparation.
Purpose
We conducted a prospective clinical trial to compare macrophage imaging with 64Cu-DOTATATE PET/CT and metabolic imaging with 18F-FDG PET/CT in patients with suspected or previously diagnosed cardiac sarcoidosis.
Methods
We included 66 patients >18 years: 22 with suspected cardiac sarcoidosis, 22 with previously diagnosed cardiac sarcoidosis (within 1.5 years before inclusion), and 22 controls without known inflammatory heart disease. Patients with suspected and previously diagnosed cardiac sarcoidosis underwent both scans; controls underwent 64Cu-DOTATATE PET/CT only. Two expert nuclear medicine physicians performed blinded scan readings.
Results
The median age was 55.2 years (82% men) in suspected cardiac sarcoidosis, 57.4 years (91% men) in previously diagnosed cardiac sarcoidosis, and 57.2 years (91% men) in controls. The median scan interval was 9 days (IQR 6-18). In suspected cardiac sarcoidosis, scans agreed on the final interpretation (active vs. no active cardiac sarcoidosis) in 20/22 patients (91%), showing substantial agreement (Cohen’s kappa=0.70). In previously diagnosed cardiac sarcoidosis, scans agreed on the final image interpretation in 20/22 patients (91%), showing almost perfect agreement (Cohen’s kappa=0.82). Kappa differed despite identical agreement because it corrects for chance. Complete agreement was seen in all patients diagnosed within 6 months prior to inclusion (n=5) and all patients with a positive myocardial biopsy (n=4). No controls had 64Cu-DOTATATE uptake suggestive of active cardiac sarcoidosis, indicating high specificity. In patients with suspect foci, the myocardial-to-background ratio was 3.12 (IQR 2.79-4.97) for 18F-FDG and 3.00 (IQR 2.11-3.46) for 64Cu-DOTATATE (P=0.24). Interobserver agreement was perfect for 18F-FDG (Cohen’s kappa=1.00) and almost perfect for 64Cu-DOTATATE (Cohen’s kappa=0.84).
Conclusions
This is the first study comparing 64Cu-DOTATATE and 18F-FDG PET/CT in cardiac sarcoidosis. The tracers showed high scan interpretation agreement and strong interobserver agreement. Unlike 18F-FDG, 64Cu-DOTATATE requires no patient preparation, offering clear workflow advantages. Our findings support a potential clinical value of 64Cu-DOTATATE in diagnostic workup for suspected cardiac sarcoidosis and monitoring disease severity in established cardiac sarcoidosis.Figure