title: 18F-FDG-PET/CT in Patients Affected by Differentiated Thyroid Carcinoma with Positive Thyroglobulin Level and Negative 131I Whole Body Scan. It's Value Confirmed by a Bicentric Experience.
abstract: BACKGROUND
  18F-FDG-PET/CT applications in the field of differentiated thyroid cancer (DTC) are continuously growing.
  
  
  OBJECTIVE
  To retrospectively analyze in a wide population enrolled in two nuclear medicine centers the diagnostic value of 18F-FDG-PET/CT in patients treated with 131I and negative 131I-WBS but in presence of Tg levels higher than 1ng/ml after TSH stimulation.
  
  
  METHODS
  From September 2005 to December 2014, 154 patients affected by DTC, treated with 131I with negative 131I-WBS and Tg&amp≥1ng/ml underwent 18F-FDG-PET/CT.
  
  
  RESULTS
  66 patients (43%) had a negative 18F-FDG-PET/CT (mean Tg=7.7ng/ml; SD=9.6) and 88 (57%) a positive scan (mean Tg=169.4; SD=294.6) documenting bone, pulmonary, lymph-node metastases and local recurrences. There was no statistically significant correlation between 18F-FDGPET/ CT results and sex, previous lymphadenectomy, the "on-" or "off-therapy" state; on the contrary, there was a statistically significant correlation between PET results and primary tumor size (T1-T2 vs. T3-T4). ROC analysis showed that the highest accuracy in terms of best compromise between sensitivity and specificity (sensitivity= 71,6%; specificity=92,4%; AUC area under the curve= 0.807) is achieved when the 12ng/mL is considered the Tg cut-off value to interpret the results.
  
  
  CONCLUSIONS
  Our study confirm in a wide population that 18F-FDG-PET/CT is useful in evaluating patients affected by DTC, negative 131I-WBS and Tg&gt;1ng/ml, identifying 12ng/ml as the Tg level cut-off over which is better to perform the study.
authors.affiliation: Nuclear Medicine, University of Brescia, Spedali Civili di Brescia, P.le Spedali Civili, 1, 25123 Brescia, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Bertagna
authors.forename: Domenico
authors.initials: D
authors.lastname: Albano
authors.forename: Giovanni
authors.initials: G
authors.lastname: Bosio
authors.forename: Arnoldo
authors.initials: A
authors.lastname: Piccardo
authors.forename: Bassam
authors.initials: B
authors.lastname: Dib
authors.forename: Raffaele
authors.initials: R
authors.lastname: Giubbini
mesh_terms: D014408:Biomarkers, Tumor / Q000097:blood; D001859:Bone Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary; D008197:Lymph Node Excision; D008207:Lymphatic Metastasis / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000000981:diagnostic imaging; D000072078:Positron Emission Tomography Computed Tomography; D019275:Radiopharmaceuticals; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013954:Thyroglobulin / Q000097:blood; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D013965:Thyroidectomy; D051598:Whole Body Imaging
chemical_list: D014408:Biomarkers, Tumor; D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D013954:Thyroglobulin
keywords: Carcinoma; PET; negative iodine scan; thyroglobulin; thyroid.