Absence of late recurrences in patients with a negative first follow-up after I-131 ablation for differentiated thyroid carcinoma

Abstract

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Objectives: In the past, large retrospective studies have shown that recurrences will frequently occur more than five years after initial treatment of differentiated thyroid carcinoma. The objective of this study was to study the recurrence rate and –time in patients with differentiated thyroid carcinoma who underwent total thyroidectomy, received I-131 ablation, had negative TSH-stimulated Tg-levels and a negative I-131 whole body scan (WBS) at the first follow-up after ablation. Methods: Retrospective data from 3 hospitals from 1980 (1 hospital) or 1990 (2 hospitals) onward on initial treatment and follow-up of patients who received I-131 ablation for differentiated thyroid carcinoma were pooled. Ablation dosages varied from 1110 to 5550 MBq. 3-12 months after ablation patients returned for follow-up with an I-131 WBS (185-370 MBq) and TSH-stimulated Tg-measurement, and were followed again with I-131 WBS and TSH-stimulated at various intervals after that. Patients who tested positive for Tg-antibodies were excluded from the analysis if Tg-levels and the I-131 WBS were negative. Results: 456 patients were included. 10 patients (2.2%) developed a recurrence after an average interval of 32 months (range: 14-58 months) following administration of the ablative dosage of I-131. Recurrence was first discovered by Tg-measurement during suppression in 5 patients, by TSH-stimulated Tg-measurement in 4 patients, and by detection of a pathologic lymph node in 1 patient. Initial staging of the patients who developed a recurrence according to the TNM system was T1N0 in 1 patient, T2N0 in five patients, T3N0 in one patient, T4N0 in one patient and T1N1 in 1 patient. Conclusions: In differentiated thyroid carcinoma patients who had a negative first follow-up I-131 WBS and negative concurrent TSH-stimulated Tg-levels after I-131 ablation, recurrence is a rare event, and in our population never occurs more than 5 years after initial treatment. Beyond the first follow-up after ablation, I-131 WBS seems to have no additional diagnostic value.