Differentiated thyroid cancer (DTC) is defined as a carcinoma deriving from the follicular epithelium and retaining basic biological characteristics of healthy thyroid tissue, including expression of the sodium iodide symporter (NIS), the key cellular feature for specific iodine uptake.
RAIT is defined as the systemic administration of 131-sodium or potassium iodide (131I) for selective irradiation of thyroid remnants, microscopic DTC or other nonresectable or incompletely resectable DTC, or both purposes. Based on the primary goal of the RAIT, there are two main forms of the procedure.
Indications and contraindications radioiodine treatment of DTC
A. Definite indications
1. Unresectable iodine-avid lymph node metastases where one or more of the following is true:
- morphological imaging does not reveal location
- surgery is high-risk or contraindicated
- distant involvement is present that would indicate RAIT anyways
2. Iodine-avid pulmonary micrometastases, especially before they become visible on CT
3. Non-resectable or partially resectable iodine-avid pulmonary macrometastases
4. Non-resectable or partially resectable iodine-avid soft tissue metastases
B. Optional indications
1. Recurrent iodine-avid lymph node or distant metastases, as an adjuvant to surgery
2. Unresectable iodine-avid lymph node metastases where one or more of the following is true:
- size is small
- involvement includes numerous nodes or is widespread
3. Non-resectable or partially resectable iodine-avid bone metastases, especially when symptomatic or threatening vital structures
4. Known or suspected metastatic DTC where iodine avidity is not yet known, especially if Tg is detectable or increasinga
5. Anaplastic or poorly differentiated thyroid carcinomas that have (relevant) well-differentiated areas or express Tg, especially if symptomatic or progressiveb
1. Iodine non-avid lymph node metastases
2. Iodine non-avid lung macrometastases
3. Iodine non-avid bone metastases
3. Clinically relevant bone marrow depression when high activity RAIT is planned (relative contraindication)
4. Clinically relevant pulmonary function restriction together with expected important accumulation in lung metastases (relative contraindication)
5. Clinically relevant salivary gland restriction, especially if 131I accumulation in known lesions is questionable (relative contraindication)
CT, computed tomography; DTC, differentiated thyroid carcinoma; 131I, 131-iodine; RAIT, radioiodine therapy; Tg, thyroglobulin
aThese patients should receive an initial course of RAIT, and if the post-therapy whole-body scan is negative, RAIT should be discontinued.
bIn these patients, the indication for external beam radiotherapy and the urgency of RAIT should be considered in the decision on whether to give RAIT.
- Luster M, Clarke SE, Dietlein M, Lassmann M, Lind P, Oyen WJ, Tennvall J, Bombardieri E; European Association of Nuclear Medicine (EANM). Guidelines for radioiodine therapy of differentiated thyroid cancer. Eur J Nucl Med Mol Imaging. 2008 Oct;35(10):1941-59. [Medline]
- Jonklaas J, Cooper DS, Ain KB, Bigos T, Brierley JD, Haugen BR, Ladenson PW, Magner J, Ross DS, Skarulis MC, Steward DL, Maxon HR, Sherman SI; National Thyroid Cancer Treatment Cooperative Study Group. Radioiodine therapy in patients with stage I differentiated thyroid cancer. Thyroid. 2010 Dec;20(12):1423-4. [Medline]
Created: Feb 23, 2011.