Open-label randomized phase III trial, using a non-inferiority comparison design. After randomization,patients will receive either post-operative radioiodine ablation with an activity of 1.1 GBq (30 mCi) after stimulation by rhTSH, and then be followed-up (ablation group) or be followed-up (without postoperative radioiodine ablation) (follow-up group).

The objective is to assess the non-inferiority of the proportion of patients without tumor-related event evaluated at three years after randomisation in the absence of radioiodine ablation (follow-up group) compared to the ablation group, in patients with low-risk differentiated thyroid cancer treated with total thyroidectomy with or without lymph node dissection (pT1am N0 or Nx, pT1b N0 or Nx)

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