title: The role of postoperative Tc-99m pertechnetate scintigraphy in estimation of remnant mass and prediction of successful ablation in patients with differentiated thyroid cancer.
abstract: OBJECTIVE
  Surgery and radioactive iodine (RAI) ablation constitute the mainstay of the treatment of differentiated thyroid carcinoma (DTC). In this study, we aimed to evaluate the diagnostic value of postoperative early Tc-99m pertechnetate scanning to detect remnant thyroid tissue and predict ablation success.
  
  
  METHODS
  DTC patients evaluated with postoperative Tc-99m pertechnetate scintigraphy and treated with RAI between January 2007 and December 2014 were recruited. The results of Tc-99m pertechnetate scanning were compared with therapeutic I-131 whole-body scanning (TxWBS) and diagnostic I-131 whole-body scanning (DxWBS) performed 6-9 months after RAI.
  
  
  RESULTS
  There were 154 (21.5%) male and 563 (78.5%) female patients, with a mean age of 49.11±12.35 years. Postoperative Tc-99m pertechnetate scanning was positive in 499 patients (69.6%) and negative in 218 (30.4%) patients. There were 673 (93.9%) patients with a positive TxWBS scan and 44 (6.1%) patients with negative TxWBS scan. Considering TxWBS as the standard test, sensitivity, specificity, positive predictive value, and negative predictive value of Tc-99m pertechnetate scanning were 72.2, 70.5, 97.4, and 14.2%, respectively. DxWBS was positive in 57 (9.0%) and negative in 564 (91%) patients. Ablation dose was higher and preablation thyroglobulin was lower in patients with negative DxWBS (P=0.001 and 0.04, respectively). Overall, 171 (92.9%) of 184 patients with negative Tc-99m pertechnetate had negative DxWBS.
  
  
  CONCLUSIONS
  Postoperative Tc-99m pertechnetate scintigraphy has a high positive predictive value to detect remnant tissue in patients with DTC. Although negative Tc-99m pertechnetate scanning does not indicate removal of all thyroid tissue, it is related to successful ablation in more than 90% of patients.
authors.affiliation: Departments of aEndocrinology and Metabolism bNuclear Medicine, School of Medicine, Ankara Yildirim Beyazit University, Ankara, Turkey.
authors.forename: Didem
authors.initials: D
authors.lastname: Ozdemir
authors.forename: Fatma N
authors.initials: FN
authors.lastname: Cuhaci
authors.forename: Elif
authors.initials: E
authors.lastname: Ozdemir
authors.forename: Cevdet
authors.initials: C
authors.lastname: Aydin
authors.forename: Reyhan
authors.initials: R
authors.lastname: Ersoy
authors.forename: Seyda
authors.initials: S
authors.lastname: Turkolmez
authors.forename: Bekir
authors.initials: B
authors.lastname: Cakir
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018365:Neoplasm, Residual; D017063:Outcome Assessment, Health Care / Q000379:methods*; D011182:Postoperative Care / Q000379:methods; D011379:Prognosis; D011877:Radionuclide Imaging / Q000379:methods*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013670:Sodium Pertechnetate Tc 99m; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery*; D013965:Thyroidectomy / Q000379:methods; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D019275:Radiopharmaceuticals; D013670:Sodium Pertechnetate Tc 99m