Superiority of68Ga-DOTATATE PET/CT compared to18F-FDG PET/CT and MRI of the spine in the detection of spinal bone metastases in metastatic pheochromocytoma and/or paraganglioma

125 Aim: The aim of this study was to evaluate and compare the diagnostic performance of 68Ga-DOTA(0)-Tyr(3)-octreotate (68Ga-DOTATATE) positron emission tomography-computed tomography (PET/CT) to 18F-fluoro-2-deoxy-D-glucose (18F-FDG) PET/CT and magnetic resonance imaging (MRI) of cervical, thoracic, and lumbar spine for the detection of spinal bone metastases in metastatic pheochromocytoma and/or paraganglioma (PPGL). Methods: A total of 47 consecutive metastatic PPGL patients underwent MRI (sagittal T1w, sagittal STIR, axial T1w, and axial T2w) of the cervical, thoracic, and lumbar spine for the evaluation of spinal bone metastases between January 2014 and December 2019. Six patients were excluded (5 patients had incomplete MRI of the spine and 1 patient did not undergo 68Ga-DOTATATE PET/CT). A total of 41 patients (females: males, 19:22; mean age, 43±30 years; 26 patients harboring mutations in genes encoding subunits of succinate dehydrogenase enzyme, 10 patients tested negative for germline mutations in PPGL susceptibility genes, and in 5 patients genetic results are pending) were included in this study who also underwent 68Ga-DOTATATE PET/CT and 18F-FDG PET/CT. The mean (±standard deviation) duration between 68Ga-DOTATATE and 18F-FDG was 21±46 days, between 18F-FDG and MRI 21±46, and between 68Ga-DOTATATE and MRI 27±40 days. Per patient and per lesion detection rates of 68Ga-DOTATATE PET/CT, 18F-FDG PET/CT, and MRI of the spine was calculated. A patient was considered as abnormal or “positive” regardless of the number of positive lesions present; counting of spinal bone metastases was limited to a maximum of one lesion per vertebrae. A composite of all the imaging studies served as an imaging comparator for the calculation of detection rates. A “positive” result on any of the imaging studies was counted as true positive for the presence of the disease. For statistical analysis, the McNemar test was used to compare detection rates between 68Ga-DOTATATE PET/CT and the other imaging modalities. Two-sided p values <0.05 were considered statistically significant. Results: All patients were positive for spinal bone metastases, with 484 lesions on the imaging comparator. 68Ga-DOTATATE PET/CT demonstrated a per lesion detection rate of 401/484 [82.9%, 95% confidence interval (CI): 79.2-86.1%]. 18F-FDG PET/CT and MRI of the spine, showed significantly lower per lesion detection rates of 262/484 (54.1%, 95% CI: 49.6-58.6%; p<0.0001) and 350/484 (72.3%, 95% CI: 68.1-76.3%; p=0.001), respectively. The per patient detection rates of 68Ga-DOTATATE was 41/41 (100%, 95% CI: 91.4-100%), and that of 18F-FDG PET/CT and MRI of the spine was 36/41 (87.8%, 95% CI: 73.8-95.9%) and 39/41 (95.1%, 83.5-99.4%), respectively. Further, 68Ga-DOTATATE PET/CT was found to detect greater (26/41, 63.4%) or equal (12/41, 29.2%) lesions compared to 18F-FDG PET/CT in 38/41 (92.7%) patients whereas 68Ga-DOTATATE PET/CT was found to detect greater (21/41, 51.2%) or equal (9/41, 22.0%) lesions compared to MRI of the spine in 30/41 (73.2%) patients. The detection rates for each of the imaging modalities are summarized in Table 1. Conclusions: 68Ga-DOTATATE PET/CT showed a significantly superior detection rate of spinal bone metastases compared to 18F-FDG PET/CT and MRI of the spine. Besides providing a three-dimensional analysis of the whole body, it maybe the imaging modality of choice to evaluate metastatic spine disease especially in the treatment planning and response assessment of the molecular radionuclide therapy (mRT: 223RaCl2, 177Lu/90Y DOTA-analogs, 131I-metaiodobenzylguanidine) in patients with bone only metastatic PPGL.