Management of low-risk patients with thyroid carcinoma and detectable thyroglobulin on T4 after thyroidectomy and ablation with iodine-131

Abstract

Objective: To evaluate the positive predictive value of detectable Tg during T4 therapy (Tg on T4) in patients with thyroid cancer after total thyroidectomy and remnant ablation, discussing the work-up in this situation and the empirical indication of 131 I. Patients and methods: Initially, 234 low-risk patients [tumor ≤ 5cm, completely resected, no extensive extrathyroid invasion (pT4)] submitted to total thyroidectomy and ablation with 131 I (3.7-5.5 GBq) who presented no ectopic uptake on RxWBS were studied. Of these, 23 patients with detectable Tg on T4 (> 1ng/ml) during the first year after initial therapy were selected. Results: Metastases were detected by neck US in 7 patients, by chest CT in 2 and by US and CT in 3. Four of five patients with lung metastases upon CT had a positive RxWBS. Eleven patients with negative US and CT received a new 131 I dose (without DxWBS), and RxWBS showed ectopic uptake in 3 patients. Among the patients with negative RxWBS, 7 remained free of apparent disease and Tg was declining (5 with undetectable Tg on T4 at the end of the study). One patient presented an increase in Tg and FDG-PET was positive for lymph node and bone metastases. Conclusions: All patients with Tg on T4 > 5ng/ml presented apparent disease. In these cases, even when US and CT are negative, the administration of a therapeutic dose of 131 I (without DxWBS) and FDG-PET are recommended. Among patients with detectable Tg on T4 ≤ 5ng/ml and negative US and CT, only 12% presented ectopic uptake on RxWBS. These cases could be followed up by monitoring Tg on T4, and RxWBS and FDG-PET should only be performed if this marker does not decrease after 1-2 years. Objetivo: Avaliar o valor preditivo positivo da Tg detectável durante terapia com T4 (Tg sob T4) em pacientes com câncer de tireóide após tireoidectomia total e ablação dos remanescentes, discutindo o manuseio dessa situação e a indicação empírica de 131 I. Pacientes e métodos: Inicialmente, foram estudados 234 pacientes de baixo risco [tumor ≤ 5cm, completamente ressecado, sem invasão extratireoideana extensa (pT4)] submetidos à tireoidectomia total e ablação com 131 I (3,7-5,5 GBq) que não apresentaram captação ectópica com RxWBS. Desses, foram selecionados 23 pacientes com Tg detectável com T4 (> 1ng/ml) durante o primeiro ano após a terapia inicial. Resultados: Metástases foram detectadas em 7 pacientes pelo US cervical, em 2 pela TC de tórax e em 3 pela US e TC. Quatro de 5 pacientes com metástases pulmonares à TC tiveram um RxWBS positivo; 11 pacientes com US e TC negativos receberam uma nova dose de 131 I (sem DxWBS), e a RxWBS mostrou captação ectópica em 3 pacientes. Entre os pacientes com RxWBS negativo, 7 permaneceram livres de doença aparente e a Tg estava em declínio (5 com Tg indetectável sob T4 ao final do estudo). Um paciente apresentou aumento da Tg e o FDG-PET foi positivo para linfonodos e metástases ósseas. Conclusões: Todos os patients com Tg sob T4 > 5ng/ml apresentaram doença aparente. Nesses casos, mesmo quando a US e a TC são ne...

Thyroid nodules and differentiated thyroid cancer: update on the Brazilian consensus

“…When no abnormalities are thus found, one may decide to merely monitor the Tg behavior later or to perform a more thorough investigation based on the Tg [T4] levels and the patient risk category. In the latter case, the traditional recommendation is to perform WBS after the use of radioiodine (100 mCi Thyroid nodules and differentiated thyroid cancer (139,151); however, the latter might also be the first step (138,152,153). When negative Tg [T4] levels increase to levels above 1 ng/ml following TSH-induced stimulation and metastases are not found at the initial assessment, conservative management is recommended when Tg is less than 10 ng/ml following discontinuation of T4 or 5 ng/ml with use of recombinant TSH (91,124,125,138).…”

“…When the Tg levels are higher, a more thorough investigation is recommended, as mentioned above. Many patients with elevated Tg and no apparent disease progress late into complete remission (91,112,124,125,138,151,152,154).…”

“…Thyroid nodules and differentiated thyroid cancer the clinical outcome will be most likely be satisfactory (91,112,124,138,151,154). Finally, the patients with undetectable stimulated Tg should be monitored as if they were in complete remission (Recommendation B).…”