Systematic Radioiodine Administration Versus Decision of Radioiodine Treatment Guided by a Post-operative Work-up

Inclusion Criteria: * Subgroup of patients with differentiated thyroid cancer and intermediate-risk defined as follows according to TNM 2017: * Papillary thyroid cancer (PTC) without aggressive subtype, follicular thyroid cancer (FTC) (with \< 4 foci of vascular invasion) or Hürthle cell carcinoma (HCC) * T1b or T2 with minimal extra-thyroid extension into the perithyroidal soft tissues and/or pN1 with largest nodal dimension between 2 and 10 mm, without extra-capsular invasion and with a number of metastatic nodes ≤ 10 * T1aN1 with largest nodal dimension between 2 and 10 mm, without extra-capsular invasion and with a number of metastatic nodes ≤ 10 * Patient treated by total thyroidectomy with macroscopically complete tumor resection (R0 or R1) ± neck dissection * Total thyroidectomy performed within 6 to 14 10 weeks before randomization * Patient with or without anti-thyroglobulin antibodies (TgAb) * No known distant metastases * Normal post-operative neck ultrasound (US) or if doubtful US, negative cytology and normal Tg value (\<10 ng/ml) in FNA washout fluid * Post-operative LT4 treatment initiated at least 6 weeks before randomization * Performance Status 0 or 1 * Patients aged 18 years or older * Signed informed consent form * Patient who agrees to be followed annually during 5 years * Patient affiliated to the French social security system Exclusion Criteria: * • Patients with: * medullary or anaplastic thyroid cancer * or poorly differentiated carcino…