Korean J Intern Med.  2020 Sep;35(5):1164-1172. 10.3904/kjim.2018.173.

The clinical meaning of pre- and post-ablation thyroglobulin levels at first radioiodine therapy in patients with papillary thyroid cancer

Affiliations
  • 1Departments of Internal Medicine, Chonnam National University Medical School, Gwangju, Korea
  • 2Departments of, Surgery Medicine, Chonnam National University Medical School, Gwangju, Korea
  • 3Departments of, Nuclear Medicine, Chonnam National University Medical School, Gwangju, Korea

Abstract

Background/Aims
This study was conducted to identify prognostic factors in patients with papillary thyroid cancer (PTC) at the time of first radioactive iodine (RAI) therapy, and to evaluate the clinical value of the thyroglobulin (Tg) increase after RAI.
Methods
Serum Tg was sampled prior to (pre-Tg) and 7 days after RAI (post-Tg) in 680 patients with PTC. Patients were classified into excellent response (ER), biochemical incomplete response (BCIR), structural incomplete response (SIR), and indeterminate response (IR) groups using dynamic risk stratification at 6 to 18 months after RAI therapy.
Results
After RAI therapy, 514 patients (75.6%) had an ER, 34 (5.0%) had a BCIR, 13 (2.0%) had an SIR, and 119 (17.5%) had an IR. Pre-Tg level was significantly different among the groups, with the highest level being in the SIR group, followed by the BCIR, IR, and ER groups. However, post-Tg levels were not different among the groups. Post-Tg level increased significantly after RAI therapy compared to the pre-Tg level (mean 13.8 ± 32.2 ng/mL vs. 2.5 ± 8.9 ng/mL). In 422 patients whose pre-Tg level was < 1 ng/mL, 205 had post-Tg levels < 1 ng/mL, while 167 had post-Tg levels of 1 to 10 ng/mL, and 50 had levels > 10 ng/mL. No difference was observed in the response to therapy. Differences in RAI dose and uptake pattern were observed among the three groups.
Conclusions
Pre-Tg was useful as a prognostic factor in patients with PTC. In patients with low pre-Tg, increased post-Tg may reflect remnant tissue and does not help predict the prognosis.

Keyword

Thyroid cancer; papillary; Radioactive iodine therapy; Thyroglobulin; Prognosis; Therapeutic response
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