title: Recurrence detection in differentiated thyroid cancer patients with elevated serum level of antithyroglobulin antibody: special emphasis on using (18)F-FDG PET/CT.
abstract: OBJECTIVE
  A clinical challenge is presented by differentiated thyroid cancer (DTC) patients who show increased serum antithyroglobulin antibody (TgAb) level with undetectable thyroglobulin (Tg) and negative radioiodine whole body scan (I-WBS). The aim of this study is to investigate the recurrence in DTC patients with elevated TgAb by using (18)F-FDG PET/CT (PET/CT) in addition to I-WBS and neck ultrasonography (USG).
  
  
  METHODS
  A total of 276 TgAb+ patients were enrolled. Recurrence was assessed and compared between TgAb+ and TgAb- patients. TgAb+ patients were further categorized into two groups of 35-140 U/ml (Group A) and 140 U/ml or greater (Group B), according to receiver operating characteristic (ROC) curve analysis. Tumoural status was evaluated regarding the TgAb positivity and the degree of increase of TgAb.
  
  
  RESULTS
  Thirty-seven (13.4%) of 276 TgAb+ patients were finally diagnosed with recurrence, compared with 21 (13.5%) of 156 TgAb- patients (P = 0.987). There was a correlation between TgAb level and recurrence (P = 0.032). Recurrence was more common in Group B than Group A (27.8% and 9.9%, respectively, P = 0.001). Recurrence was found in 37.5% of 24 TgAb+/Tg- patients who showed a gradually increasing tendency in serial measurements of TgAb. Sixteen cervical foci (21.1%) missed on neck USG and 17 lesions (22.4%) located outside the neck were additionally detected with PET/CT in TgAb+ patients.
  
  
  CONCLUSIONS
  TgAb plays a complementary role to Tg in the detection of recurrence of DTC. Tumour recurrence was more frequent in patients with elevated TgAb level over 140 U/ml or a trend toward increasing levels. PET/CT could provide additional information to I-WBS and neck USG in detecting tumour recurrence in patients with elevated TgAb.
authors.affiliation: Department of Nuclear Medicine, Kyungpook National University Hospital, Daegu, Republic of Korea.
authors.forename: Ji Hyoung
authors.initials: JH
authors.lastname: Seo
authors.forename: Sang Woo
authors.initials: SW
authors.lastname: Lee
authors.forename: Byeong-Cheol
authors.initials: BC
authors.lastname: Ahn
authors.forename: Jaetae
authors.initials: J
authors.lastname: Lee
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001323:Autoantibodies / Q000097:blood*; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography; D015995:Prevalence; D013954:Thyroglobulin / Q000097:blood / Q000276:immunology*; D013964:Thyroid Neoplasms / Q000175:diagnosis / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed; D051598:Whole Body Imaging
chemical_list: D001323:Autoantibodies; C006606:anti-thyroglobulin; D019788:Fluorodeoxyglucose F18; D013954:Thyroglobulin