Sequential follow-up of serum thyroglobulin and whole body scan in thyroid cancer patients without initial metastasis.
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.
Huang
Shu-Hua
SH
Department of Nuclear Medicine, Chang Gung Memorial Hospital-Ksohsiung Medical Center, Chang Gung University College of Medicine, Kaohsiung, Taiwan.
Wang
Pei-Wen
PW
Huang
Yu-Erh
YE
Chou
Fong-Fu
FF
Liu
Rue-Tsuan
RT
Tung
Shih-Chen
SC
Chen
Jung-Fu
JF
Kuo
Ming-Chun
MC
Hsieh
Jing-Rong
JR
Hsieh
Hsin-Hung
HH
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
D013954:Thyroglobulin; D013974:Thyroxine