This is a multi-centre, randomised, non-inferiority, phase III study in patients with low risk differentiated thyroid cancer.

Patients will be identified via oncology multidisciplinary team meetings. There will be two sources of patients in the trial, with the same histological diagnoses and prognosis (i.e. recurrence risk):

• Group 1: Patients who have already had a HT for thyroid problems and are then subsequently diagnosed with low risk DTC will be randomised 1:1 to undergo surveillance only OR a second operation to remove the rest of their thyroid gland (two-stage total thyroidectomy).
• Group 2: Patients diagnosed with low risk DTC using cytology (Thy5) but no surgery performed will be randomised 1:1 to have either a hemi-thyroidectomy OR a single-stage total thyroidectomy.

The overall aim of the trial is to determine whether hemithyroidectomy is an acceptable and cost-effective surgical procedure compared to total thyroidectomy in low risk thyroid cancer. Overall, 456 patients will be recruited to the trial. Patients will be initially be followed up post-surgery then 12 monthly for 6 years.

Group 1 (HT already performed prior to diagnosis)

Inclusion criteria

• Aged 16 or over

Papillary thyroid cancer:

• pT1b-2 (≤4cm) irrespective of molecular genetic markers

• R0 resection (clinically excised but microscopic R1 resected tumours at discretion of the local MDT)

• cN0 or pN0, pNX & pN1a (≤5 foci, no extranodal spread)

• Confined to thyroid or minimal extrathyroidal extension

• No higher risk histological variants on morphology (small foci allowed at the discretion of the local MDT)

• No angioinvasion NB. PTC is still eligible where microscopic invasion of endothelial lined small capillary vascular spaces and lymphatic channels are present. It becomes ineligible in the rare instances when there is definite invasion of a larger vascular structure such as a vein with smooth muscle in its wall.

• Encapsulated FVPTC with capsular invasion only

• Micro-PTC (≤1cm)

  • multifocal
  • unifocal with pN1a (≤5 foci; no extranodal spread)

Follicular thyroid cancer (FTC), including oncocytic or Hürthle cell carcinoma:

• pT1b-2 (≤4cm) irrespective of molecular genetic markers

  - Minimally invasive, with capsular invasion +/- minimal (≤4 foci) vascular invasion (the latter is now called encapsulated angioinvasive and is at the discretion of the MDT)

• Confined to thyroid or minimal extrathyroidal extension

Exclusion criteria

• >4cm

• unifocal pT1a (≤1cm) PTC or FTC (unless pN1a as above)

• NIFTP (non-invasive follicular thyroid neoplasm with papillary-like nuclear features)

• Anaplastic, poorly differentiated or medullary thyroid carcinoma

• R2

• gross extrathyroidal extension

• pT4 or macroscopic tumour invasion of loco-regional tissues or structures

• pN1a with >5 foci or extranodal spread

• pN1b

• M1

• Aggressive PTC with any of the following features:

  • Widely invasive
  • Poorly differentiated
  • Anaplastic
  • predominance of Tall cell, Columnar cell, Hobnail, Diffuse sclerosing and other higher risk variants

• FTC, including oncocytic or Hürthle cell cancer with any of the following features:

  • Minimally invasive with extensive vascular invasion (now called encapsulated angioinvasive) (>4 foci)
  • Widely invasive
  • Poorly differentiated
  • Anaplastic

Group 2 (DTC on cytology or after core biopsy, who has not had prior thyroid surgery yet)

Inclusion criteria

• Aged 16 or over
• 'low risk' differentiated thyroid cancer confirmed by cytology or core biopsy.
• cT1b-2 irrespective of molecular genetic markers
• cN0
• Contralateral lobe without suspicious nodule(s) (U2, or U3/U4 with Thy2 on FNAC)

Exclusion criteria

• M1