Outcome of ablation of thyroid remnants with 100 mCi (3.7 GBq) iodine-131 in patients with thyroid cancer

Ann Nucl Med. 2005 May;19(3):247-50. doi: 10.1007/BF02984614.

Abstract

A retrospective study was conducted on 186 patients with differentiated thyroid cancer without metastases who received an ablative dose of 100 mCi (3.7 GBq) iodine-131 after total thyroidectomy. Six months to one year after ablation, 155/186 patients (83%) had a negative scan. Diagnostic scanning with 5 mCi (185 MBq) performed 72 h or 3 months before ablation did not interfere with treatment success compared to patients not submitted to pre-therapy scanning. Pre-ablation cervical uptake values < 2% were associated with a higher ablation efficacy (94%), from 2 to 5% showed 80% success and values > 5%, 60% (p < 0.05). There were no significant differences between the responsive and no responsive groups in terms of age, sex, histological type or size of the primary tumor. 11% of the patients with low stimulated Tg (< 2 ng/ml) presented discrete thyroid bed uptake on follow-up diagnostic scan (< 0.5%) without definitive residual disease and 89% had negative uptake on scan. The patients with Tg > 2 ng/ml presented thyroid bed (10/12) or ectopic (2/12) uptake on follow-up diagnostic scan. An ablative dose of 100 mCi shows a high rate of efficacy, especially when cervical uptake is < 2%; no difference was noted between patients assessed by scan within 72 h or 3 months before treatment and those not scanned; follow-up diagnostic scan can be avoided in low risk patients with stimulated Tg < 2 ng/ml.

MeSH terms

  • Adolescent
  • Adult
  • Age Distribution
  • Aged
  • Brazil / epidemiology
  • Carcinoma / epidemiology*
  • Carcinoma / prevention & control*
  • Dose-Response Relationship, Radiation
  • Female
  • Humans
  • Iodine Radioisotopes / administration & dosage*
  • Male
  • Middle Aged
  • Neoplasm Recurrence, Local / epidemiology*
  • Neoplasm Recurrence, Local / prevention & control*
  • Postoperative Care
  • Radiopharmaceuticals / administration & dosage
  • Radiotherapy Dosage
  • Radiotherapy, Adjuvant / statistics & numerical data
  • Retrospective Studies
  • Risk Assessment / methods*
  • Risk Factors
  • Sex Distribution
  • Thyroid Neoplasms / epidemiology*
  • Thyroid Neoplasms / surgery*
  • Treatment Outcome

Substances

  • Iodine Radioisotopes
  • Radiopharmaceuticals