Medications After Thyroid Cancer Surgery
All patients require levothyroxine (L-T4) therapy immediately after thyroidectomy for thyroid cancer, with the specific TSH suppression target determined by cancer type and risk stratification. 1
Levothyroxine: Universal Post-Thyroidectomy Medication
Initiation and Administration
- Start levothyroxine immediately after total thyroidectomy for all thyroid cancer patients 1, 2
- Administer as a single daily dose on an empty stomach, one-half to one hour before breakfast with a full glass of water 2
- Continue levothyroxine on the morning of any future surgeries without interruption 3
Dosing Strategy by Cancer Type
Differentiated Thyroid Cancer (DTC) - Papillary, Follicular, Oncocytic
The TSH suppression target depends on risk stratification 1:
High-Risk Patients:
- Maintain TSH <0.1 mIU/L with suppressive doses of levothyroxine 1
- This aggressive suppression decreases progression and recurrence rates 1
- Continue suppression for patients with persistent structural disease 1, 3
Intermediate-Risk Patients:
Low-Risk Patients with Excellent Response:
- Maintain TSH in low-normal range of 0.5-2.0 mIU/L 1
- Can shift from suppressive to replacement therapy after initial treatment success 1
Medullary Thyroid Cancer (MTC)
- Replacement therapy only—maintain TSH in normal range (0.5-2.0 mIU/L) 1
- TSH suppression is NOT appropriate for MTC because C cells lack TSH receptors 3
- The goal is thyroid hormone replacement, not suppression 1
Anaplastic and Poorly Differentiated Thyroid Cancer
- TSH suppressive therapy with L-T4 should be initiated immediately following surgery 1
- Maintain suppressive dosing similar to high-risk DTC 1
Dosing Considerations
- Average dose requirement for thyroid cancer patients post-ablation: 2.11 mcg/kg/day (higher than benign hypothyroidism at 1.63 mcg/kg/day) 4
- Peak therapeutic effect may not be attained for 4-6 weeks 2
- Dosage adjustments should be based on TSH and free-T4 levels measured serially 1
Radioactive Iodine (RAI) Therapy
Indications by Risk Level
High-Risk Patients:
- Administer 100-200 mCi (3.7-7.4 GBq) of ¹³¹I after TSH stimulation 1
- RAI is recommended for patients with distant metastases 1
Intermediate-Risk Patients:
Low-Risk Patients:
- RAI is NOT recommended for small (≤1 cm) intrathyroidal DTC without locoregional metastases 1
- If given, use low activities (30 mCi, 1.1 GBq) 1
RAI-Refractory Disease
- Non-RAI-avid lesions or those that lose RAI uptake should be considered RAI-refractory 1
- These patients require alternative systemic therapies 1
Systemic Therapies for Advanced/Metastatic Disease
First-Line Multikinase Inhibitors for RAI-Refractory DTC
Lenvatinib and sorafenib are the standard first-line systemic therapy for RAI-refractory differentiated thyroid cancer 1:
- Lenvatinib: ESMO-MCBS score of 3 1
- Sorafenib: ESMO-MCBS score of 2 1
- Response rates range from 14% to 65% across various tyrosine kinase inhibitors 1, 5
Targeted Therapies for Specific Mutations
- Dabrafenib for BRAF mutations 5
- Selpercatinib for RET mutations 5
- These are used in patients with advanced thyroid carcinoma harboring specific genetic alterations 5
Medullary Thyroid Cancer Systemic Therapy
- Vandetanib is FDA and EMA approved for locally advanced/metastatic MTC 1
- Should be considered for patients with incurable disease 1
- Traditional chemotherapy has <20% response rate and is not recommended 1
Adjunctive Medications
Bone Metastases Management
- Bisphosphonates or denosumab can be used alone or combined with locoregional treatments for thyroid cancer-related bone metastases 1
Important Caveat
Decisions on multikinase inhibitors must be based on patient preference after careful discussion of expected benefits and risks 1. These agents have significant toxicity profiles, and clinical trial enrollment should be encouraged when appropriate 1.