IoN- Is Ablative Radio-iodine Necessary for Low Risk Differentiated Thyroid Cancer Patients

TNM eligibility is assessed against TNM7 (7th edition 2009) or TNM8 (8th edition 2017, in use in the UK from 01/01/2018). Eligibility Criteria using TNM7: Inclusion criteria: * Histological confirmation of well differentiated thyroid carcinoma: MDT decision for inclusion based on overall clinico-pathological assessment is critical. * R0 total thyroidectomy (in one or two stages, no residual disease present; Rx at the discretion of the MDT) within the last 6 months * Negative pregnancy test in women of child bearing potential * Aged 16 or over * WHO performance status 0 - 2, self-caring * Histological confirmation of differentiated thyroid carcinoma:MDT decision for inclusion based on overall clinico-pathological assessment * Papillary thyroid cancer (PTC): * Non aggressive histological features (small foci of aggressive histology allowed at the discretion of the MDT) * pT1a (≤1cm) unifocal with positive level VI lymph nodes (pN1a) * pT1a(m): all individual foci ≤1cm * pT1b and pT1b(m): \>1-2cm * pT2 and pT2(m): \>2-4cm * pT3 and pT3(m): \>4cm confined to the thyroid * pT3 R0 +/- (m): any size with minimal ETE if recommended by the MDT * pN0 * pN1a * pNX * Follicular thyroid cancer (FTC) (including oncocytic or Hürthle cell cancer): o minimally invasive FTC -which are considered low risk and are recommended by the specialist MDT based on overall clinico-pathological assessment * pT1b and pT2: \>1-4cm intrathyroidal * pT3 R0:any size up to 4 cm with minimal ETE if recommended by the MDT * Histological material available for Central Review (see section 9.7) * Willing to use contraception for the duration of the trial until 6 months post radioiodine treatment (for females) or 4 months post treatment (for males) (see section 6.4.2), if allocated to the ablation group. NB: Multifocal tumours (≥2 foci) of all histological types should be designated with "(m)", and the size of the largest focus determines the classification (as described in the TNM 7th edition). For example, if there are two foci, one 0.8cm and the other 3cm, the classification is based on the 3cm focus; i.e. pT2(m). Exclusion criteria: * pT1a - Papillary and Follicular carcinoma which is unifocal and ≤1cm in size, without any positive nodes or unfavourable clinical features, treated by lobectomy. * Up to 4cm non-invasive Encapsulated Follicular Variant of Papillary Thyroid Cancer (eFVPTC) with no capsular or vascular invasion (\>4 cm can be included at the discretion of the MDT) * non-invasive follicular tumour with papillary-like nuclei (NIFTP) * Anaplastic, poorly differentiated or medullary carcinoma * R1 or R2 thyroidectomy * Patients with: * pN1b * M1 * Aggressive Papillary thyroid cancer with any of the following features: * Widely invasive * Poorly differentiated * Anaplastic * Tall cell * Columnar cell * Diffuse sclerosing variants * Follicular thyroid cancer/Hürthle cell cancer with any of the following features: * Tumours greater than 4cm * Widely invasive * Poorly differentiated * Anaplastic * Incomplete resection or lobectomy * pT4a and pT4b or macroscopic and microscopic tumour invasion of loco-regional tissues or structures * Pregnant women or women who are breast feeding * Patients who have had CT performed with iv contrast less than 2-3 months before ablation * Previous treatment for thyroid cancer (except surgery in last 6 months) * Previous malignancies with limited life expectancy or likely to interfere with the patient's ability to be able to comply with treatment and/or follow-up for at least 5 years * The following GI conditions: dysphagia, oesophageal stricture, active gastritis, gastric erosions, peptic ulcer, suspected reduced gastrointestinal motility * MDT decision against ablation or suitability for trial in light of severe co-morbid condition/s including: * Unstable angina * Recent myocardial infarction or cerebrovascular accident (CVA) * Severe labile hypertension * Any patient who cannot comply with radiation protection including: * patients with learning difficulties * patients with dementia * patients with a tracheostomy that require nursing care * patients requiring frequent nursing/ medical supervision Eligibility Criteria using TNM8: Inclusion criteria: * Histological confirmation of well differentiated thyroid carcinoma: MDT decision for inclusion based on overall clinico-pathological assessment is critical. * R0 total thyroidectomy (in one or two stages, no residual disease present; Rx at the discretion of the MDT) within the last 6 months * Negative pregnancy test in women of child bearing potential * Aged 16 or over * WHO performance status 0 - 2, self-caring * Histological confirmation of differentiated thyroid carcinoma:MDT decision for inclusion based on overall clinico-pathological assessment * Papillary thyroid cancer (PTC): * Non aggressive histological features (small foci of aggressive histology allowed at the discretion of the MDT) * pT1a (≤1cm) unifocal with positive level VI lymph nodes (pN1a) * pT1a(m): all individual foci ≤1cm * pT1b and pT1b(m): \>1-2cm * pT2 and pT2(m): \>2-4cm * pT3a and pT3a(m): \>4cm confined to thyroid * pT1a/1b/2/3 (where minimal microscopic extra thyroidal extension (ETE) does not change the T score) +/- (m): any size with minimal ETE if recommended by the MDT * pN0 * pN1a * pNX * Follicular thyroid cancer (FTC) (including oncocytic or Hürthle cell cancer): o minimally invasive FTC -which are considered low risk and are recommended by the specialist MDT based on overall clinico-pathological assessment * pT1b and pT2: \>1-4cm intrathyroidal * pT1a/1b/2/3a (where minimal microscopic ETE does not change the T score): any size up to 4 cm with minimal ETE if recommended by the MDT * Histological material available for Central Review (see section 9.7) * Willing to use contraception for the duration of the trial until 6 months post radioiodine treatment (for females) or 4 months post treatment (for males) (see section 6.4.2), if allocated to the ablation group. Exclusion criteria: * pT1a - Papillary and Follicular carcinoma which is unifocal and ≤1cm in size, without any positive nodes or unfavourable clinical features, treated by lobectomy. * Up to 4cm non-invasive Encapsulated Follicular Variant of Papillary Thyroid Cancer (eFVPTC) with no capsular or vascular invasion (\>4 cm can be included at the discretion of the MDT) * non-invasive follicular tumour with papillary-like nuclei (NIFTP) * Anaplastic, poorly differentiated or medullary carcinoma * R1 or R2 thyroidectomy * Patients with: * pN1a with level VII involvement * pN1b * M1 * Aggressive Papillary thyroid cancer with any of the following features: * Widely invasive * Poorly differentiated * Anaplastic * Tall cell * Columnar cell * Diffuse sclerosing variants * Follicular thyroid cancer/Hürthle cell cancer with any of the following features: * Tumours greater than 4cm * Widely invasive * Poorly differentiated * Anaplastic * Incomplete resection or lobectomy * pT3b, pT4a and pT4b or macroscopic and microscopic tumour invasion of loco-regional tissues or structures * Pregnant women or women who are breast feeding * Patients who have had CT performed with iv contrast less than 2-3 months before ablation * Previous treatment for thyroid cancer (except surgery in last 6 months) * Previous malignancies with limited life expectancy or likely to interfere with the patient's ability to be able to comply with treatment and/or follow-up for at least 5 years * The following GI conditions: dysphagia, oesophageal stricture, active gastritis, gastric erosions, peptic ulcer, suspected reduced gastrointestinal motility * MDT decision against ablation or suitability for trial in light of severe co-morbid condition/s including: * Unstable angina * Recent myocardial infarction or cerebrovascular accident (CVA) * Severe labile hypertension * Any patient who cannot comply with radiation protection including: * patients with learning difficulties * patients with dementia * patients with a tracheostomy that require nursing care * patients requiring frequent nursing/ medical supervision