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Thyroid. 2012 Apr 24. [Epub ahead of print]

Even without additional therapy, serum thyroglobulin levels often decline for years after total thyroidectomy and RAI remnant ablation.

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  • 1UNIFESP, Endocrinology, São Paulo, São Paulo, Brazil; rosaliapadovani@yahoo.com.br.


Background: Current management guidelines suggest that 6-12 months after total thyroidectomy and RAI remnant ablation, patients with differentiated thyroid cancer should be re-evaluated with serum thyroglobulin and neck ultrasonography to assess the efficacy of initial treatment and to guide subsequent management. However, if serum Tg levels can continue to decline for many years after RAI ablation, an early assessment of response to therapy could lead to excessive evaluations and treatments in patients with low level Tg values that are likely to resolve over time without additional therapies. Methods: Suppressed serum thyroglobulin were collected retrospectively in 299 differentiated thyroid cancer patients (69% female, median age 46 yrs, 92% papillary thyroid cancer, median 7 year follow-up) that received no additional treatments beyond total thyroidectomy, radioactive remnant ablation, and levothyroxine suppressive therapy. The primary endpoints were the time required to achieve the lowest Tg (nadir Tg) and the time required to achieve a suppressed Tg less than 1 ng/mL. Results: The nadir suppressed Tg was achieved by 6 months in 58% of the patients and by 12 months in 75% of the patients. The remaining 25% of patients required 18 months or longer to reach the nadir Tg. However, in the subgroup of patients that eventually reached a nadir suppressed Tg < 1 ng/mL (n=223 patients), this goal was achieved by 6 months in 81%, by 12 months in 91%, and by 18 months in 94%. In patients with a 6 month suppressed Tg of 1-5 ng/mL, 54% eventually developed a suppressed Tg < 1 ng/mL without additional therapy. Conclusions: In patients selected for continued observation, serum Tg levels often continue to decline for several years after total thyroidectomy and RAI remnant ablation. While a 6-12 month assessment of the response to initial therapy is useful in patient management, strong consideration should be given to continued observation without additional therapy in patients with well differentiated thyroid cancer that have 6 month suppressed Tg values of 1-5 ng/mL without structurally identifiable disease.

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