Comparison of Dosimetry After rhTSH or Withdrawal of Thyroid Hormone in Metastatic or Locally Advanced Thyroid Cancer
Comparison of Dosimetry After rhTSH or Withdrawal of Thyroid Hormone in Metastatic or Locally Advanced Thyroid Cancer
Metastases of thyroid cancer with iodine uptake are treated with repeated activity of I-131
 administered after thyroid hormone withdrawal. The goal of thyroid hormone withdrawal is to
 treat patients with elevated thyrotropin stimulated hormone (TSH), a hormone secreted by the
 pituitary, a gland just located under the brain. Another way to obtain elevated TSH levels is
 to perform intramuscular injection of recombinant human TSH, a hormone produced
 pharmaceutically. The goal of this study is to know whether the radioiodine uptake by the
 metastases is similar after rhTSH administration or after thyroid hormone withdrawal.
Patients will undergo a rhTSH stimulation, staying on thyroid hormone treatment. Following 2
 administration of rhTSH an injection of I-124 will be performed. Positron emission tomography
 with computed tomography scans (PET/CT), blood tests, and measurements of whole body
 radioactivity will occurred during the 4 to 96 hours following I-124 administration in order
 to perform dosimetry (i.e.) to estimate the radiation dose delivered to the metastases. After
 4 weeks under thyroid hormones patients will undergo thyroid hormone withdrawal and a new
 administration of I-124 will be performed. The same dosimetry study will be realized with
 PET/CT, blood tests, and measurements of whole body radioactivity. A therapeutic activity of
 I-131will then be administered followed by whole body scan realized 24 to 72 hours after the
 administration of I-131. Dosimetry studies will be compared in order to determine whether
 rhTSH stimulation can replace thyroid hormone withdrawal for the treatment of distant
 metastases.
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