68Ga-DOTATATE PET/CT for the detection of inflammation of large arteries: correlation with 18F-FDG, calcium burden and risk factors

Background: Ga-[1,4,7,10-tetraazacyclododecane-N, N', N '', N'''-tetraacetic acid]-d-Phe(1), Tyr(3)-octreotate (DOTATATE) positron emission tomography (PET) is commonly used for the visualization of somatostatin receptor (SSTR)-positive neuroendocrine tumors. SSTR is also known to be expressed on macrophages, which play a major role in inflammatory processes in the walls of coronary arteries and large vessels. Therefore, imaging SSTR expression has the potential to visualize vulnerable plaques. We assessed Ga-68-DOTATATE accumulation in large vessels in comparison to F-18-2-fluorodeoxyglucose (FDG) uptake, calcified plaques (CPs), and cardiovascular risk factors. Methods: Sixteen consecutive patients with neuroendocrine tumors or thyroid cancer underwent both Ga-68-DOTATATE and F-18-FDG PET/CT for staging or restaging purposes. Detailed clinical data, including common cardiovascular risk factors, were recorded. For a separate assessment, they were divided into a high-risk and a low-risk group. In each patient, we calculated the maximum target-to-background ratio (TBR) of eight arterial segments. The correlation of the TBRmean of both tracers with risk factors including plaque burden was assessed. Results: The mean TBR of Ga-68-DOTATATE in all large arteries correlated significantly with the presence of CPs (r = 0.52; p < 0.05), hypertension (r = 0.60; p < 0.05), age (r = 0.56; p < 0.05), and uptake of F-18-FDG (r = 0.64; p < 0.01). There was one significant correlation between F-18-FDG uptake and hypertension (0.58; p < 0.05). Out of the 37 sites with the highest focal Ga-68-DOTATATE uptake, 16 (43.2%) also had focal F-18-FDG uptake. Of 39 sites with the highest F-18-FDG uptake, only 11 (28.2%) had a colocalized Ga-68-DOTATATE accumulation. Conclusions: In this series of cancer patients, we found a stronger association of increased Ga-68-DOTATATE uptake with known risk factors of cardiovascular disease as compared to F-18-FDG, suggesting a potential role for plaque imaging in large arteries. Strikingly, we found that focal uptake of Ga-68-DOTATATE and F-18-FDG does not colocalize in a significant number of lesions.