Postoperative stimulated thyroglobulin of less than 1 ng/ml as a criterion to spare low-risk patients with papillary thyroid cancer from radioactive iodine ablation.
BACKGROUND
Stimulated thyroglobulin (Tg) ≤1 ng/mL after thyroidectomy (after L-thyroxine [L-T4] withdrawal or administration of recombinant human thyrotropin [rhTSH]) has been proposed as a criterion to spare patients with papillary thyroid cancer (PTC), who are at low risk of recurrence, from ablation with iodine-131 ((131)I). The objective of this prospective study was to evaluate the recurrence rate using this approach.


METHODS
This prospective study included 136 patients with PTC who underwent total thyroidectomy with apparently complete tumor resection and who presented no signs of persistent disease after surgery. The patients were classified as low risk of recurrence (nonaggressive histology, T1b-3 N0 M0). All patients had stimulated Tg ≤1 ng/mL, negative anti-Tg antibodies (TgAb), and neck ultrasound (US) showing no anomalies ~16 weeks after thyroidectomy, and none of them were submitted to ablation with (131)I. The time of follow-up ranged from 12 to 72 months (median: 44 months).


RESULTS
Among the patients studied, 134 (98.5%) continued to have serum Tg concentrations of <1 ng/mL during therapy with L-T4 (Tg/T4) and had negative TgAb and neck US. Lymph node metastases were detected by neck US in one patient. An increase of TgAb was observed in another patient, but she has not developed apparent disease to date. There was only one case of recurrence even among the 60 patients with tumors >4 cm or minimal extrathyroid invasion (T3 N0 M0).


CONCLUSIONS
Low-risk patients with PTC who have stimulated Tg ≤1 ng/mL after thyroidectomy do not require ablation with (131)I.
Instituto de Ensino e Pesquisa da Santa Casa de Belo Horizonte, Belo Horizonte, Minas Gerais, Brazil. pedrorosario@globo.com
Pedro Weslley
PW
Rosario
Augusto Flávio Campos
AF
Mineiro Filho
Brenda Sá Senna
BS
Prates
Lívia Cristina Oliveira
LC
Silva
Maria Regina
MR
Calsolari
D000293:Adolescent; D000328:Adult; D000368:Aged; D002277:Carcinoma / Q000000981:diagnostic imaging / Q000532:radiotherapy / Q000601:surgery*; D002291:Carcinoma, Papillary; D002648:Child; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D009333:Neck / Q000000981:diagnostic imaging; D011182:Postoperative Care; D011446:Prospective Studies; D012008:Recurrence; D013954:Thyroglobulin / Q000097:blood* / Q000276:immunology; D000077273:Thyroid Cancer, Papillary; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy / Q000601:surgery*; D013965:Thyroidectomy; D014463:Ultrasonography
D007457:Iodine Radioisotopes; D013954:Thyroglobulin