Potential clinical utility of Ga-68-DOTATATE PET/CT for detection and response assessment in cardiac sarcoidosis

Background Somatostatin receptor is expressed in sarcoid granulomas, and preliminary clinical studies have shown that myocardial sarcoidosis can be identified on somatostatin receptor-targeted PET. We examined the potential clinical use of Ga-68-DOTATATE PET/CT for diagnosis and response assessment in cardiac sarcoidosis compared to F-18-FDG PET/CT. Methods Eleven cardiac sarcoidosis patients with F-18-FDG PET/CT were prospectively enrolled for cardiac Ga-68-DOTATATE PET/CT. The two PET/CT studies were interpreted independently and were compared for patient-level and segment-level concordance, as well as for the degree of radiotracer uptake. Follow-up Ga-68-DOTATATE PET/CT was performed in eight patients. Results Patient-level concordance was 91%: ten patients had multifocal DOTATATE uptake (active cardiac sarcoidosis) and one patient showed diffuse DOTATATE uptake. Segment-level agreement was 77.1% (Kappa 0.53 +/- 0.07). The SUVmax-to-blood pool ratio was lower on Ga-68-DOTATATE PET/CT (3.2 +/- 0.6 vs. 4.9 +/- 1.5, P = 0.006 on paired t test). Follow-up Ga-68-DOTATATE PET/CT showed one case of complete response and one case of partial response, while F-18-FDG PET/CT showed four cases of response, including three with complete response. Conclusion Compared to F-18-FDG PET/CT, Ga-68-DOTATATE PET/CT can identify active cardiac sarcoidosis with high patient-level concordance, but with moderate segment-level concordance, low signal-to-background ratio, and underestimation of treatment response.