Who Orders Radioactive Iodine Therapy
Radioactive iodine therapy for differentiated thyroid carcinoma after thyroidectomy is ordered by the multidisciplinary thyroid cancer treatment team, which typically includes an endocrinologist, nuclear medicine physician, and/or endocrine surgeon, with the nuclear medicine physician ultimately administering the treatment. 1, 2
Clinical Decision-Making Framework
The ordering process follows a risk-stratified approach based on post-surgical pathology and staging:
High-Risk Patients (Definitive RAI Indication)
The following patients require RAI therapy ordered by the treating team 3, 1:
- Known distant metastases
- Gross extrathyroidal extension (T4 disease)
- Documented lymph node metastases
- Primary tumor >4 cm
- Positive surgical margins
- Macroscopic multifocal disease
Dosing: 100-200 mCi (3.7-7.4 GBq) with TSH stimulation 3, 2
Intermediate-Risk Patients (RAI Generally Recommended)
RAI is typically ordered for 3, 1:
- T1 tumors >1 cm or T2 tumors
- Aggressive histologic variants (tall cell, columnar cell, poorly differentiated)
- Vascular invasion
- Cervical lymph node involvement
Dosing: 30-100 mCi (1.1-3.7 GBq), with preference for ≥100 mCi 3, 1, 2
Low-Risk Patients (RAI Optional, Individualized)
The decision requires careful consideration by the treatment team 3, 1:
- T1 tumors >1 cm without high-risk features
- Multifocal disease with all foci >1 cm
Dosing if given: 30 mCi (1.1 GBq) with rhTSH preferred 3, 1
Very Low-Risk Patients (RAI Not Indicated)
RAI should not be ordered for 3, 1, 2:
- Unifocal pT1a tumors (<1 cm) without other risk features
- N0/NX disease without aggressive histology
Timing and Preparation Protocol
RAI is ordered 2-12 weeks post-thyroidectomy 3, 2. The ordering physician must specify:
- TSH stimulation method: Either recombinant human TSH (rhTSH, preferred) or thyroid hormone withdrawal 1, 2
- rhTSH protocol: 0.9 mg IM on Day 1 and Day 2, with RAI administration on Day 3 1, 2
- Target TSH level: >30 mIU/L before RAI administration 1
Key Ordering Considerations
Common Pitfalls to Avoid
- Do not order RAI without confirming pregnancy status - pregnancy is an absolute contraindication 2, 4
- Avoid iodinated contrast before RAI unless essential, as it interferes with uptake 3
- Do not order RAI for anaplastic thyroid carcinoma - these tumors do not concentrate iodine and RAI is ineffective 3
- Ensure all palpable neck disease is surgically resected before ordering RAI 3
Institutional Requirements
The nuclear medicine physician administers the actual treatment and performs post-treatment whole-body scanning 2, 4. However, the initial decision and order typically comes from the endocrinologist or endocrine surgeon managing the patient's thyroid cancer 1, 5.
Post-Treatment Monitoring
After RAI administration, the ordering physician maintains responsibility for 1, 2:
- TSH suppression therapy management
- Thyroglobulin monitoring at 6 and 12 months
- Neck ultrasound surveillance
- Response assessment at 6-18 months
The ordering physician must balance the benefits of RAI (reduced recurrence, improved surveillance) against potential risks (secondary malignancies with cumulative doses >600 mCi) 3, 6.