title: [(68)Ga]DOTATATE PET/MRI and [(18)F]FDG PET/CT are complementary and superior to diffusion-weighted MR imaging for radioactive-iodine-refractory differentiated thyroid cancer.
abstract: OBJECTIVE
  The purpose of this study was to determine whether [(68)Ga]DOTATATE PET/MRI with diffusion-weighted imaging (DWI) can replace or complement [(18)F]FDG PET/CT in patients with radioactive-iodine (RAI)-refractory differentiated thyroid cancer (DTC).
  
  
  METHODS
  The study population comprised 12 patients with elevated thyroglobulin and a negative RAI scan after thyroidectomy and RAI remnant ablation who underwent both [(18)F]FDG PET/CT and [(68)Ga]DOTATATE PET/MRI within 8 weeks of each other. The presence of recurrent cancer was evaluated on a per-patient, per-organ and per-lesion basis. Histology, and prior and follow-up examinations served as the standard of reference.
  
  
  RESULTS
  Recurrent or metastatic tumour was confirmed in 11 of the 12 patients. [(68)Ga]DOTATATE PET(/MRI) correctly identified the tumour burden in all 11 patients, whereas in one patient local relapse was missed by [(18)F]FDG PET/CT. In the lesion-based analysis, overall lesion detection rates were 79/85 (93 %), 69/85 (81 %) and 27/82 (33 %) for [(18)F]FDG PET/CT, [(68)Ga]DOTATATE PET/MRI and DWI, respectively. [(18)F]FDG PET(/CT) was superior to [(68)Ga]DOTATATE PET(/MRI) in the overall evaluation and in the detection of pulmonary metastases. In the detection of extrapulmonary metastases, [(68)Ga]DOTATATE PET(/MRI) showed a higher sensitivity than [(18)F]FDG PET(/CT), at the cost of lower specificity. DWI achieved only poor sensitivity and was significantly inferior to [(18)F]FDG PET in the lesion-based evaluation in the detection of both extrapulmonary and pulmonary metastases.
  
  
  CONCLUSIONS
  [(18)F]FDG PET/CT was more sensitive than [(68)Ga]DOTATATE PET/MRI in the evaluation of RAI-refractory DTC, mostly because of its excellent ability to detect lung metastases. In the evaluation of extrapulmonary lesions, [(68)Ga]DOTATATE PET(/MRI) was more sensitive and [(18)F]FDG PET(/CT) more specific. Furthermore, DWI did not provide additional information and cannot replace [(18)F]FDG PET for postoperative monitoring of patients with suspected RAI-refractory DTC.
authors.affiliation: Department of Nuclear Medicine, University Hospital Münster, Münster, Germany. vrachal@uni-muenster.de.|DFG CRC 656 'Molecular Cardiovascular Imaging', Westfälische Wilhelms University Münster, Münster, Germany. vrachal@uni-muenster.de.
authors.forename: Alexis
authors.initials: A
authors.lastname: Vrachimis
authors.affiliation: Department of Nuclear Medicine, University Hospital Münster, Münster, Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: Stegger
authors.affiliation: Department of Nuclear Medicine, University Hospital Münster, Münster, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Wenning
authors.affiliation: Department of Nuclear Medicine, University Hospital Münster, Münster, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Noto
authors.affiliation: Institute for Clinical Radiology, University Hospital Münster, Münster, Germany.
authors.forename: Matthias Christian
authors.initials: MC
authors.lastname: Burg
authors.affiliation: Department of Nuclear Medicine, University Hospital Münster, Münster, Germany.
authors.forename: Julia Renate
authors.initials: JR
authors.lastname: Konnert
authors.affiliation: Institute for Clinical Radiology, University Hospital Münster, Münster, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Allkemper
authors.affiliation: Institute for Clinical Radiology, University Hospital Münster, Münster, Germany.
authors.forename: Walter
authors.initials: W
authors.lastname: Heindel
authors.affiliation: Department of Nuclear Medicine, University Hospital Münster, Münster, Germany.
authors.forename: Burkhard
authors.initials: B
authors.lastname: Riemann
authors.affiliation: Department of Nuclear Medicine, University Hospital Münster, Münster, Germany.|DFG CRC 656 'Molecular Cardiovascular Imaging', Westfälische Wilhelms University Münster, Münster, Germany.|European Institute of Molecular Imaging, Westfälische Wilhelms University Münster, Münster, Germany.|DFG EXC 1003 'Cells in Motion' Cluster of Excellence, Westfälische Wilhelms University Münster, Münster, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Schäfers
authors.affiliation: Department of Nuclear Medicine, University Hospital Münster, Münster, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Weckesser
mesh_terms: D000328:Adult; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009942:Organometallic Compounds; D000072078:Positron Emission Tomography Computed Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000627:therapeutic use; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000628:therapy*
chemical_list: D007457:Iodine Radioisotopes; D009942:Organometallic Compounds; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; C513399:gallium Ga 68 dotatate
keywords: DTC; DWI; Extrapulmonary metastases; Pulmonary metastases