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A Follow-Up Strategy for Patients with an Excellent Response to Initial Therapy for Differentiated Thyroid Carcinoma: Less Is Better.

BACKGROUND
The risk of recurrence in patients with differentiated thyroid cancer (DTC) can be estimated based on their response to initial therapy. The aim of this study was to evaluate an adequate follow-up strategy for DTC patients with an excellent response by assessing the characteristics of structural recurrence.


METHODS
This historical cohort study included 1359 DTC patients who had excellent response to total thyroidectomy with radioactive iodine remnant ablation.


RESULTS
Among 1359 patients, 703 (54%) patients were classified as stage I according to the seventh tumor node metastasis staging system, and 987 (73%) patients were classified as intermediate risk according to the American Thyroid Association's risk stratification after initial therapy. During a median of 8.7 years of follow-up, only 13 (1%) patients were confirmed to have structural recurrence. All of the recurrences were locoregional disease, and there were no distant metastases. Recurrences were detected late at a median of 5.5 years after the initial surgery (range 3.6-10.7 years). All structural recurrences were detected on neck ultrasonography. Non-stimulated serum thyroglobulin (Tg) was detectable (≥0.2 ng/mL) in four (31%) patients, and serum anti-Tg antibodies were positive in one (8%) patient. However, non-stimulated serum Tg levels were stably low (<0.2 ng/mL) in eight (62%) patients when recurrences were detected. In addition to these 13 patients, 14 patients also presented with biochemical persistent disease at the end of follow-up.


CONCLUSIONS
Recurrences of DTC in patients with an excellent response to initial therapy were detected relatively late. The intensity and frequency of follow-up of neck ultrasonography as well as serum Tg and anti-Tg antibody measurements should be reduced, especially within five years of the initial therapy, in DTC patients who have an excellent response.