The following factors need to be considered when determining the extent of thyroidectomy for DTC surgery.
1. the size of the tumor.
2. the presence or absence of invasion of surrounding tissues
3, the presence of lymph nodes and distant metastases.
4, unifocal or multifocal.
5. history of radiation exposure during childhood.
6, family history of thyroid cancer or thyroid cancer syndrome.
7. other risk factors such as gender and pathological subtypes.
The principles of surgical management should be refined according to the clinical TNM (cTNM) stage, the risk of tumor death/recurrence, the advantages and disadvantages of various surgical procedures and the patient’s wishes, and should not be generalized.
The main thyroidectomy procedures for DTC include total/near-total thyroidectomy and thyroid lobectomy + isthmus. Total thyroidectomy is the removal of all thyroid tissue with no visible thyroid tissue remaining, while subtotal thyroidectomy is the removal of almost all visible thyroid tissue (with <1g of non-neoplastic thyroid tissue, such as the laryngeal nerve into the larynx or the parathyroid gland).
Total/near-total thyroidectomy may provide the following benefits for patients with DTC.
1. treatment of multifocal lesions in a single visit
2. facilitates postoperative monitoring of tumor recurrence and metastasis
3. facilitating postoperative 131I therapy.
4. reduce the chance of tumor recurrence and reoperation (especially for patients with intermediate and high-risk DTC), thus avoiding the increased incidence of serious complications due to reoperation.
5. accurately assessing the postoperative staging and risk stratification of patients. On the other hand, permanent hypothyroidism will inevitably occur after total/proximal total thyroidectomy; moreover, this procedure requires a higher level of surgeon expertise and an increased probability of impaired postoperative parathyroid function and/or laryngeal recurrent nerve injury.
Suggested indications for total/near-total thyroidectomy for DTC include.
1. history of head and neck radiation exposure or radioactive fallout exposure during childhood.
2, primary foci >4 cm in maximum diameter.
3, multiple cancerous foci, especially bilateral ones.
4, poor pathological subtypes, such as: hypercellular, columnar cell, diffuse sclerosing, solid subtype of PTC, extensive infiltrative type of FTC, and hypofractionated thyroid cancer.
5. having distant metastases and requiring postoperative 131I treatment.
6, with bilateral lymph node metastasis in the neck.
7.Extra-glandular invasion (such as tracheal, esophageal, carotid artery or mediastinal invasion).
The relative indications for total/near-total thyroidectomy are: maximum tumor diameter between 1-4 cm, with high risk factors for thyroid cancer or combined with contralateral thyroid nodules.
Compared with total/near-total thyroidectomy, lobectomy + isthmus is more favorable to protect parathyroid function, reduce contralateral laryngeal nerve injury, and preserve some thyroid function; however, this procedure may miss microscopic lesions in the contralateral thyroid gland, which is not favorable for postoperative monitoring by serum Tg and 131I whole-body imaging, and if 131I therapy is assessed to be required after surgery, a reoperation to remove the residual thyroid gland.
Therefore, the recommended indications for thyroid lobectomy + isthmus are: single DTC confined to one lobe of the gland with a primary tumor ≤1 cm, low risk of recurrence, no history of childhood head and neck radiation exposure, no cervical lymph node metastases or distant metastases, and no nodules in the contralateral lobe. The relative indications for thyroid lobectomy + isthmus are: single DTC confined to one lobe with a primary tumor ≤ 4 cm, low risk of recurrence, no nodules in the contralateral lobe, and microinfiltrative FTC.