Differentiated Thyroid Cancer: is There a Need for Radioiodine Ablation in Low Risk Patients?

Inclusion Criteria: 1. Patients with differentiated thyroid cancer (papillary, follicular or with Hurthle cells) in the absence of aggressive histological subtypes (poorly differentiated, tall-clear-cylindric cell, diffuse sclerosing or with an anaplastic component) 2. Patients having undergone a total thyroidectomy with complete (R0) tumor resection, with or without lymph node neck dissection 3. Total thyroidectomy performed 2 to 5 months before inclusion 4. Patients with low risk of recurrence: pT1amN0 or pT1amNx with a sum of the size of the lesions above 1 cm and equal to or less than 2 cm, or pT1bN0 or pT1bNx (TNM 2010 classification). 5. Post-operative neck ultrasound (performed 2 to 5 months after surgery) showing the absence of abnormalities in the lateral lymph node compartments, or if abnormalities, no lymph nodes with abnormal cytology and/or thyroglobulin concentration in the aspirate fluid \> 10 ng/mL 6. Age \>=18 years 7. Performance status of 0 or 1 8. Patients who signed the informed consent 9. Patients who can be followed-up annually during 5 years in order to assess the objectives of the study 10. Women of childbearing age should have a negative pregnancy test before any radioiodine administration 11. Both patients with or without thyroglobulin antibodies are eligible Exclusion Criteria: 1. Patients having undergone less than a total thyroidectomy 2. Patients with aggressive histotype (poorly differentiated, tall-clear-cylindric cell, diffuse sclerosing, or with an anaplastic component) 3. Patients having undergone total thyroidectomy less than 2 months or more than 5 months before inclusion 4. Patients with cancer classified as pT1a unifocal (in which ablation is not necessary), or pT1N1, pT2, pT3, pT4 or N1 (who have a higher risk of recurrence) (classification TNM 2010) 5. Patient with known distant metastasis 6. Abnormal post-operative neck ultrasound of the lateral lymph node compartments 7. Patients with another malignancy not in remission for at least 2 years (except for in situ cervix uterine cancer, basocellular skin cancer) 8. Patients with a recent history of drugs affecting thyroid function, including injection of radiocontrast agents during the last 8 weeks. 9. Patients previously treated with radioactive iodine or who previously underwent a whole body scan with radioactive iodine 10. Pregnant or breast feeding women 11. Subject with any kind of disorder that may compromise his/her ability to give written informed consent and/or to comply with study procedures