title: Efficacy of high therapeutic doses of iodine-131 in patients with differentiated thyroid cancer and detectable serum thyroglobulin.
abstract: Serum thyroglobulin (Tg) is usually the best marker of residual or metastatic disease after treatment of differentiated thyroid cancer. We evaluated the effect of so-called blind therapeutic doses of iodine-131 in patients with detectable Tg during suppressive levothyroxine treatment (Tg-on), and in patients with a negative diagnostic scintigram but detectable Tg during the hypothyroid phase (Tg-off). Twenty-two patients with differentiated thyroid carcinoma underwent total thyroidectomy and radioiodine ablation. During the follow-up, six patients with detectable Tg-on and 16 patients with detectable Tg-off were identified. All patients were treated with a blind therapeutic dose of 7,400 MBq iodine-131. Diagnostic scintigrams were compared with post-treatment scintigrams. Tg-off was measured in 16 cases, 1 year after the administration of the blind therapeutic dose, at the time of the follow-up diagnostic scintigram. Six patients were followed up by Tg-on only. Post-therapy scintigrams revealed previously undiagnosed local recurrence or distant metastases in 13/22 cases (59%); the remaining nine post-therapy scintigrams were negative. At the time of the blind therapeutic doses, Tg-off values ranged from 8 to 608 microg/l. After 1 year of follow-up, Tg-off decreased in 14/16 (88%) patients. In all patients who were followed by Tg-on only (n=6), a decrease in Tg values was measured. It is concluded that blind therapeutic doses resulted in a decrease in Tg levels in the majority of patients with suspected recurrence or metastases. The post-treatment scintigrams revealed pathological uptake in 59% of patients.
authors: Department of Nuclear Medicine, University Medical Center Utrecht, The Netherlands.
authors: B
authors: B
authors: de Keizer
authors: H P
authors: HP
authors: Koppeschaar
authors: P M
authors: PM
authors: Zelissen
authors: C J
authors: CJ
authors: Lips
authors: P P
authors: PP
authors: van Rijk
authors: A
authors: A
authors: van Dijk
authors: J M
authors: JM
authors: de Klerk
mesh_terms: D000328:Adult; D000368:Aged; D018265:Carcinoma, Papillary, Follicular / Q000378:metabolism / Q000532:radiotherapy*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D013954:Thyroglobulin / Q000378:metabolism*; D013964:Thyroid Neoplasms / Q000378:metabolism / Q000532:radiotherapy*; D013965:Thyroidectomy; D013974:Thyroxine / Q000627:therapeutic use; D014915:Whole-Body Counting
chemical_list: D007457:Iodine Radioisotopes; D013954:Thyroglobulin; D013974:Thyroxine