Clinical significance of thyroglobulin autoantibodies enhancement in patients with differentiated thyroid cancer after thyroidectomy and radioiodine therapy

Purpose: to evaluate the clinical utility of antithyroglobulin antibodies (TgAb) as a tumor marker in patients with differentiated thyroid cancer (DTC) after thyroidectomy and radioiodine ablation. Patients and methods. From 345 consecutive DTC patients after thyroidectomy and radioiodine ablation we select ed 148 patients with elevated TgAb level (with distant metastasis n = 93, without distant metastasis n = 55). Serum TgAb concentration was measured before radioiodine ablation and then every time before 131I treatment (RIT) or diagnostic 131I whole body scanning (WBS). Results were compared with serum thyroglobulin (Tg) concentration, neck echography, lung and bone roentgenography and 131I WBS findings. Results. TgAb level was elevated in 21% DTC patients before 131I ablation. The other 22% with initially normal TgAb displayed their rising during followup. In absence of distant metastasis TgAb declined after 1 st–2 nd cycle of RIT (an average 8.9 months after 131I ablation). Persistance or rising of TgAb in the longer term was associated with detectable thyroid remnant, residual tumor or metastatic lymph nodes. In case of negative TgAb status after sugery an increase of TgAb during first 3–6 months after ablation indicated mostly a response to the rise of Tg antigen secondary to 131I ablation. A rise TgAb in the longer term (after 3rd–5th cycles of RIT) indicated to residual or recurrent disease in 86% cases. In patients with distant metastasis there were no correlation between change in TgAb concentration and clinical sta tus, including the rate of regression of metastatic disease. But in case of low or undetectable Tg and permanent high TgAb level only TgAb indicated the presence of disease. Conclusion: persistence or rising TgAb in longer term after 131I ablation can serve as surrogate tumor marker of per sistent or recurrent disease. It is critical to measure TgAb concentration, especially in patients with low or unde tectable Tg, because in these cases TgAb appears to be the only serum DTC tumor marker.

thyroid cancer, thyroglobulin, antithyroglobulin antibodies

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