title: Sequential follow-up of serum thyroglobulin and whole body scan in thyroid cancer patients without initial metastasis.
abstract: OBJECTIVE
  To investigate the usefulness of whole body scan (WBS) and serum thyroglobulin (Tg) measurement after thyroxine withdrawal during sequential follow-ups in patients with differentiated thyroid cancer (DTC).
  
  
  METHODS
  Two hundred and sixty-five consecutive DTC patients were enrolled. They were previously treated with near-total thyroidectomy and I-131 remnant ablation, without initial metastases or Tg antibodies. All had the first follow-up WBS and serum Tg measurement 6-12 months after initial treatment, and 165 patients received the second follow-up without further therapy. Positive/negative predictive values (PPV/NPV) were calculated by the outcome of patients being followed up for more than 8 years (mean+/-SD: 133+/-26 months).
  
  
  RESULTS
  Serum Tg levels while the patients were off thyroxine therapy decreased spontaneously in 39.3% of the cases without further therapy. The NPV of the first follow-up serum Tg level was excellent: <2 microg/L and <0.5 microg/L were 95.1% and 98.2%, respectively. However, the PPV of the first follow-up serum Tg level was low: >10 microg/L and 2-10 microg/L were 40% and 9.6%, respectively. The trend of Tg levels was more informative; the PPV was 62.5% in cases with an increase of serum Tg of >10 microg/L and 16.6% with an increase of <5 microg/L. However, decreasing Tg levels may associate with rapid deterioration of disease, in which cases decrease of Tg indicated dedifferentiation of the tumor. The diagnostic WBS showed the same picture in 91.5% of the patients. Only one patient (0.6%) turned from negative study to positive during the follow-up. In the meanwhile his serum Tg levels increased from 0.56 to 13.6 microg/L.
  
  
  CONCLUSIONS
  It is most informative when both the trend and the levels of Tg during sequential follow-up are considered. The diagnostic WBS may be performed for selected patients with indication based on Tg levels to localize the disease.
authors.affiliation: Department of Nuclear Medicine, Chang Gung Memorial Hospital-Ksohsiung Medical Center, Chang Gung University College of Medicine, Kaohsiung, Taiwan.
authors.forename: Shu-Hua
authors.initials: SH
authors.lastname: Huang
authors.forename: Pei-Wen
authors.initials: PW
authors.lastname: Wang
authors.forename: Yu-Erh
authors.initials: YE
authors.lastname: Huang
authors.forename: Fong-Fu
authors.initials: FF
authors.lastname: Chou
authors.forename: Rue-Tsuan
authors.initials: RT
authors.lastname: Liu
authors.forename: Shih-Chen
authors.initials: SC
authors.lastname: Tung
authors.forename: Jung-Fu
authors.initials: JF
authors.lastname: Chen
authors.forename: Ming-Chun
authors.initials: MC
authors.lastname: Kuo
authors.forename: Jing-Rong
authors.initials: JR
authors.lastname: Hsieh
authors.forename: Hsin-Hung
authors.initials: HH
authors.lastname: Hsieh
mesh_terms: D000328:Adult; D000368:Aged; D002291:Carcinoma, Papillary / Q000000981:diagnostic imaging* / Q000628:therapy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis / Q000000981:diagnostic imaging; D011237:Predictive Value of Tests; D011877:Radionuclide Imaging; D013375:Substance Withdrawal Syndrome; D013954:Thyroglobulin / Q000097:blood*; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000628:therapy; D013974:Thyroxine / Q000627:therapeutic use; D051598:Whole Body Imaging
chemical_list: D013954:Thyroglobulin; D013974:Thyroxine