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


METHODS
Initially, 234 low-risk patients [tumor < 5cm, completely resected, no extensive extrathyroid invasion (pT4)] submitted to total thyroidectomy and ablation with 131I (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 131I 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 131I (without DxWBS) and FDG-PET are recommended. Among patients with detectable Tg on T4 <or= 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.
Rosário
Pedro W S
PW
Endocrinology Service, Department of Thyroid, Santa Casa de Belo Horizonte, MG. pedrorosario@globo.com
Borges
Michelle A R
MA
Costa
Graciela B C
GB
Rezende
Leonardo L
LL
Padrão
Eduardo L
EL
Barroso
Alvaro L
AL
Purisch
Saulo
S
D000293:Adolescent; D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000032:analysis; D002277:Carcinoma / Q000175:diagnosis / Q000532:radiotherapy / Q000628:therapy*; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008175:Lung Neoplasms / Q000556:secondary; D008198:Lymph Nodes / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis / Q000175:diagnosis / Q000628:therapy; D011237:Predictive Value of Tests; D013954:Thyroglobulin / Q000032:analysis*; D013964:Thyroid Neoplasms / Q000175:diagnosis / Q000532:radiotherapy / Q000628:therapy*; D013965:Thyroidectomy; D013974:Thyroxine / Q000032:analysis / Q000627:therapeutic use*; D014057:Tomography, X-Ray Computed; D014463:Ultrasonography
D014408:Biomarkers, Tumor; D007457:Iodine Radioisotopes; D013954:Thyroglobulin; D013974:Thyroxine