The utility of radioiodine scans prior to iodine 131 ablation in patients with well-differentiated thyroid cancer

Thyroid. 2009 Aug;19(8):849-55. doi: 10.1089/thy.2008.0419.


Background: The utility of radioiodine (RAI) scans prior to (131)I ablation is controversial. The objective of this study was to evaluate the utility of RAI scans prior to (131)I ablation in patient with well-differentiated thyroid cancer.

Method: All RAI scans performed prior to (131)I ablation from July 2000 to November 2006 at Washington Hospital Center were reviewed retrospectively. Patients were excluded who were suspected of having 1) loco-regional disease, 2) distant metastases, and/or 3) physiological uptake that might alter management prior to the pre-ablation RAI scans. RAI scans were performed either 24 hours after dosing with 37-148 MBq of (123)I or 48 hours after dosing with 37-148 MBq of (131)I with imaging of the whole body, the thyroid bed/neck with a pinhole collimator, and the neck and chest with a parallel-hole collimator. One reviewer blindly evaluated each set of scans using six criteria, and for the purpose of this study, the thresholds for each criterion for which the patient's management may have been altered prior to (131)I ablation are noted in parentheses: 1) the number of foci of RAI uptake in thyroid bed/neck (0 or > or =6), 2) the location(s) of these foci in the thyroid bed/neck (outside the thyroid bed), 3) the size of the largest foci in thyroid bed/neck (> or =1 lobe), 4) the percent uptake in the thyroid bed/neck (> or =15%), 5) uptake suggestive of distant metastases, and 6) significant altered biodistribution (e.g., any breast, marked salivary gland, or marked gastrointestinal uptake).

Results: Of 355 sets of scans reviewed, 53% of patients had findings on the RAI scans that might have altered the patient's management prior to their (131)I ablation. The data grouped by the criteria noted above were 1) 12% with six or more foci suggesting local metastases and 6% (22) with no focal uptake, 2) 14% with suggestion of lymph node metastases, 3) 1.1% with at least one focus > or =1 lobe, 4) 8% with > or =15% uptake, 5) 4% with distant metastases, 6) 16% demonstrating altered distribution with 6% breast, 3% salivary, 10% GI, and 0.3% urinary bladder.

Conclusion: Pre-ablation RAI scans demonstrate a significant number of findings that may alter the management of patients with well-differentiated thyroid cancer prior to (131)I ablation.

MeSH terms

  • Ablation Techniques
  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Female
  • Humans
  • Iodine Radioisotopes / therapeutic use*
  • Male
  • Medical Oncology / methods
  • Middle Aged
  • Radionuclide Imaging
  • Retrospective Studies
  • Single-Blind Method
  • Thyroid Gland / diagnostic imaging
  • Thyroid Neoplasms / diagnosis*
  • Thyroid Neoplasms / diagnostic imaging*
  • Thyroid Neoplasms / radiotherapy*
  • Whole Body Imaging


  • Iodine Radioisotopes