Inclusion Criteria:

1. Patients with thyroid cancer and known measurable (>1cm) distant metastases
demonstrating radioiodine uptake on a previous whole body scan

2. Patients planned for a therapeutic activity of 131I after thyroid hormone withdrawal

3. Age >18 years

4. Previous treatment with radioiodine more than 6 months before inclusion.

5. Serum TSH level <0.5 mU/L

6. Normal renal function with a creatinine clearance estimation using the
Cockcroft-Gault formula > 60 ml/ml

7. Effective means of contraception for female patient, at risk of pregnancy

8. Written informed consent

Exclusion Criteria:

1. Patients whose majority of tumoral lesions disclose FDG uptake without radioactive
iodine uptake

2. Iodine excess (< 50 μg/dl)

3. Large or diffuse bone or brain metastases

4. Patients with multiple small tumor foci less than 1 cm in diameter, such as miliary
spread to the lungs

5. Patients already included in a therapeutic trial with an experimental medicine

6. Pregnancy and breast feeding patients

7. Subject with any kind of disorder that compromises the ability of the subject to give
written informed consent and/or to comply with study procedures

8. Treatment with antivitamin k