title: The intensity of 18FDG uptake does not predict tumor growth in patients with metastatic differentiated thyroid cancer.
abstract: OBJECTIVE
  In patients with metastatic differentiated thyroid carcinoma (DTC), fluorodeoxyglucose (FDG) uptake as well as age, tumor size and radioactive iodine (RAI) uptake are prognostic factors for survival. High FDG uptake is a poor prognostic factor and lesions with high FDG uptake are often considered aggressive, but the predictive value of FDG uptake for morphological progression is unknown. The principal aim of this retrospective single center study was to determine whether the intensity of FDG uptake was correlated on a per lesion analysis with tumor growth rate (TGR) expressed as the percentage of increase in tumor size during 1 year (1-year TGR).
  
  
  METHODS
  Fifty five patients with DTC were included between July 2012 and May 2014 with the following criteria: (i) at least one distant metastasis measuring ≥ 1 cm in diameter on CT scan (ii) evaluation by FDG-positron emission tomography/computed tomography (PET/CT) performed at our center (iii) at least one CT or another FDG-PET/CT performed 3 to 12 months after the reference FDG-PET/CT in the absence of systemic or local treatment between the two imaging procedures.
  
  
  RESULTS
  One hundred and fifty-six metastatic lesions located in lungs (63), neck lymph nodes (28), chest lymph nodes (42), bone (11), liver (2) and other sites (12) were studied. The median size was 16 mm, median SUVmax/lesion: 8.7; median metabolic tumor volume/lesion (Metab.TV/lesion): 3.7 cm3. The median 1-year TGR was 40.68 %. SUVmax and Metab.TV/lesion were not correlated to their 1-year TGR (p = 0.38 and p = 0.74 respectively). Among single patients with multiple lesions, the lesions with the highest SUVmax/lesion or the highest Metab.TV/lesion did not disclose the higher 1-year TGR.
  
  
  CONCLUSIONS
  The intensity of FDG uptake on a per lesion analysis is not correlated to its 1-year TGR and cannot be used as a surrogate marker of tumour progression.
authors: Department of Nuclear Medicine and Endocrine Oncology, Gustave Roussy and Université Paris Saclay, 114 Rue Edouard Vaillant, 94805, Villejuif, France. marie.terroir-cassou-mounat@gustaveroussy.fr.
authors: Marie
authors: M
authors: Terroir
authors: Department of Biostatistics and Epidemiology, Gustave Roussy, University Paris Sud, 114 Rue Edouard Vaillant, 94805, Villejuif, France.
authors: Isabelle
authors: I
authors: Borget
authors: Department of Radiology, Gustave Roussy, 114 Rue Edouard Vaillant, 94805, Villejuif, France.
authors: François
authors: F
authors: Bidault
authors: Department of Physic, Gustave Roussy, 114 Rue Edouard Vaillant, 94805, Villejuif, France.
authors: Marcel
authors: M
authors: Ricard
authors: Department of Interventional Radiology, 114 Rue Edouard Vaillant, 94805, Villejuif, France.
authors: Frédéric
authors: F
authors: Deschamps
authors: Department of Surgery, Gustave Roussy, 114 Rue Edouard Vaillant, 94805, Villejuif, France.
authors: Dana
authors: D
authors: Hartl
authors: Department of Interventional Radiology, 114 Rue Edouard Vaillant, 94805, Villejuif, France.
authors: Lambros
authors: L
authors: Tselikas
authors: Department of Nuclear Medicine and Endocrine Oncology, Gustave Roussy and Université Paris Saclay, 114 Rue Edouard Vaillant, 94805, Villejuif, France.
authors: Laurent
authors: L
authors: Dercle
authors: Department of Nuclear Medicine and Endocrine Oncology, Gustave Roussy and Université Paris Saclay, 114 Rue Edouard Vaillant, 94805, Villejuif, France.
authors: Jean
authors: J
authors: Lumbroso
authors: Department of Nuclear Medicine and Endocrine Oncology, Gustave Roussy and Université Paris Saclay, 114 Rue Edouard Vaillant, 94805, Villejuif, France.
authors: Eric
authors: E
authors: Baudin
authors: Department of Nuclear Medicine and Endocrine Oncology, Gustave Roussy and Université Paris Saclay, 114 Rue Edouard Vaillant, 94805, Villejuif, France.
authors: Amandine
authors: A
authors: Berdelou
authors: Department of Nuclear Medicine and Endocrine Oncology, Gustave Roussy and Université Paris Saclay, 114 Rue Edouard Vaillant, 94805, Villejuif, France.
authors: Désirée
authors: D
authors: Deandreis
authors: Department of Nuclear Medicine and Endocrine Oncology, Gustave Roussy and Université Paris Saclay, 114 Rue Edouard Vaillant, 94805, Villejuif, France.
authors: Martin
authors: M
authors: Schlumberger
authors: Department of Nuclear Medicine and Endocrine Oncology, Gustave Roussy and Université Paris Saclay, 114 Rue Edouard Vaillant, 94805, Villejuif, France.
authors: Sophie
authors: S
authors: Leboulleux
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002277:Carcinoma / Q000000981:diagnostic imaging* / Q000473:pathology; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D000072078:Positron Emission Tomography Computed Tomography; D019275:Radiopharmaceuticals; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: 18FDG PET/CT; Differentiated thyroid cancer; Metastases; Tumor growth rate