Follow-up regimen of differentiated thyroid carcinoma in thyroidectomized patients after thyroid hormone withdrawal

For differentiated, nonmedullary thyroid carcinoma, postsurgical ablation of thyroid remnants and treatment of residual tumor and metastases with 131I is a potentially curative therapy. The aim of this study was to optimize the diagnostic protocol for the follow-up of thyroidectomized patients.

Two hundred fifty-four patients (187 females, 67 males; mean age, 45 y; range, 8-83 y) were studied retrospectively for a mean follow-up period of 2.7 y (range, 1-12.5 y). An evaluation study consisted of a low-dose 131I diagnostic procedure under hyperthyroid conditions (thyroid-stimulating hormone > 30 MicroU/mL), 201TI scintigraphy, and measurement of thyroglobulin (Tg) under hypothyroid conditions. A total of 254 preablation studies (1 study per patient) and 586 follow-up studies (average number of studies, 2.3 per patient) were evaluated.

Before ablation, low-dose 131I screening was useful to estimate the size of the thyroid remnant. Low Tg levels (<10 pmol/L) indicated the absence of metastases. After ablation, undetectable Tg levels indicated the absence of tumor recurrence. When Tg levels were high (>10 pmol/L), local recurrence or metastases were always observed, providing the basis for additional high-dose 131I therapy. In these patients, 201TI imaging did not provide a significant contribution to patient management. In the case of autoantibodies against Tg, both low-dose 131I screening and 201TI scintigraphy may be advocated to allow an aggressive diagnostic work-up.

Tg plays a key role in follow-up and in making decisions to treat patients with differentiated thyroid carcinoma. The role of 201TI imaging is very limited. In patients with negative low-dose 131I screening, 201TI scintigraphy can be considered when Tg is elevated or cannot be evaluated because of autoantibodies against Tg. Under such circumstances, administration of a therapeutic 131I dose without 201TI imaging can be considered.