EP32 – The ratio of serum Thyroglobulin to Tg Antibodies (Tg/TgAb) is useful as a surrogate tumor-marker of differentiated thyroid carcinoma

      Akiyama, Ichiro1; Usui, Yoshiyuki1 1 Surgery, Okayama National Hospital, Okayama, Japan   Background: Although Tg is an established tumor marker used in the management of patients with DTC, it is not useful for TgAb-positive case. Purpose and Methods: We will show the cases of DTC who underwent total thyroidectomy to describe the clinical utility of the ratio of Tg/TgAb. Results: In the case of rapid progression disease (PD), Tg increase much faster than TgAb and it makes Tg/TgAb higher. On the other hands, in the case of rapid partial response (PR) due to effective treatment, Tg decrease much faster than TgAb and it makes Tg/TgAb lower. In the case of stable disease (SD), mild PD or PR, Tg/TgAb is low and stable, because the productivity of Tg and TgAb is balanced. Discussion: Even if TgAb interfere Tg, Tg/TgAb may reflects the disease progression because TgAb change much slowly compare with Tg. It is reported that half-life period of TgAb is about 6 months to 3 years, and it is much longer than Tg. In addition, Tg/TgAb might useful to evaluate the indication of tyrosine kinase inhibitor. Conclusion: In the cases for TgAb-positive patients, especially long SD cases, the ratio of Tg/TgAb is useful as a surrogate tumor-marker of DTC.

 

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