Can a patient with a history of thyroid cancer who has undergone radioactive iodine treatment take Glucagon-like peptide-1 (GLP-1) receptor agonists?

GLP-1 Receptor Agonists in Patients with History of Thyroid Cancer Who Have Undergone Radioactive Iodine Treatment

GLP-1 receptor agonists are contraindicated in patients with a personal history of medullary thyroid carcinoma (MTC), but can generally be used in patients with a history of differentiated thyroid cancer (DTC) who have completed radioactive iodine treatment. 1

Risk Assessment Based on Thyroid Cancer Type

Differentiated Thyroid Cancer (DTC)

• Includes papillary and follicular thyroid cancers
• If patient had DTC and completed radioactive iodine treatment:
  • GLP-1 receptor agonists can be prescribed
  • No specific contraindication exists for this cancer type
  • Regular thyroid surveillance should continue as per standard post-thyroid cancer protocols 1

Medullary Thyroid Cancer (MTC)

• Absolute contraindication for GLP-1 receptor agonists
• FDA Black Box Warning explicitly states GLP-1 receptor agonists are contraindicated in:
  • Patients with personal history of MTC
  • Patients with Multiple Endocrine Neoplasia syndrome type 2 (MEN2) 1

Evidence-Based Rationale

The contraindication for MTC is based on preclinical studies showing GLP-1 receptor agonists increased the risk of C-cell tumors in rodents. However, the FDA Black Box Warning does not extend to differentiated thyroid cancers (papillary, follicular) 1.

Recent research provides conflicting evidence regarding thyroid cancer risk:

• A 2023 French nested case-control study found increased risk of thyroid cancer with GLP-1 RA use for 1-3 years 2
• A 2024 Scandinavian cohort study of 145,410 patients found no increased risk of thyroid cancer with GLP-1 receptor agonist use (HR 0.93,95% CI 0.66-1.31) 3
• A 2024 US study found increased risk within the first year of GLP-1 RA initiation, potentially due to detection bias 4

Clinical Approach for Patients with History of Thyroid Cancer

1. Confirm thyroid cancer type:

   • If MTC: Do NOT prescribe GLP-1 receptor agonists
   • If DTC (papillary/follicular): Can consider GLP-1 receptor agonists

2. Verify completion of radioactive iodine treatment:

   • Ensure adequate follow-up showing no evidence of recurrence
   • Check most recent thyroglobulin levels are appropriate for treatment status

3. Consider alternative medications if uncertainty exists:

   • SGLT2 inhibitors may be appropriate alternatives for diabetes management 1
   • DPP-4 inhibitors can be considered with appropriate dose adjustments for renal function 1

Monitoring Recommendations

For patients with history of DTC who are prescribed GLP-1 receptor agonists:

• Continue standard thyroid cancer surveillance per guidelines
• Monitor thyroglobulin levels as normally scheduled
• No additional thyroid monitoring is specifically required due to GLP-1 RA use

Common Pitfalls to Avoid

1. Confusing DTC with MTC: Ensure accurate documentation of thyroid cancer type before prescribing
2. Unnecessary withholding of beneficial therapy: Don't withhold GLP-1 RAs from DTC patients who could benefit
3. Overlooking surveillance: Continue appropriate thyroid cancer surveillance regardless of GLP-1 RA use
4. Misinterpreting the FDA warning: The contraindication specifically applies to MTC, not all thyroid cancers

In conclusion, while GLP-1 receptor agonists carry a Black Box Warning related to medullary thyroid cancer, patients with a history of differentiated thyroid cancer who have completed radioactive iodine treatment can generally be prescribed these medications when clinically indicated.