The fundamental treatment objectives of differentiated thyroid cancer are
1. Remove the primary tumor site, diseased tissue that has spread beyond the thyroid envelope and the involved neck lymph nodes.
2. To reduce the rate of disability associated with treatment and disease.
3.Precise staging of the tumor.
4.Easy to perform I131 radiotherapy at the appropriate time after surgery.
5.It is convenient for physicians to precisely monitor the recurrence of the disease in the long term after surgery.
6.It is beneficial to control the risk of tumor recurrence and metastasis to the minimum.
It is known by standard pathological examination that 20% to 50% of patients with differentiated thyroid cancer (especially papillary carcinoma) have cervical lymph node involvement, even if the primary tumor is small or confined to the thyroid gland. Postoperative ultrasonography can detect suspicious lymph nodes in the neck in 20% to 31% of patients, and surgical options may be altered as a result. Accurate staging of the tumor is essential both to determine prognosis and to guide treatment; however, unlike other tumors, the presence of metastases does not mean that the primary site of differentiated thyroid cancer cannot be removed. Metastatic foci are sensitive to I131 radiotherapy, therefore, even if metastatic foci are present, the primary thyroid tumor and the surrounding tissues that may be involved should be removed during initial treatment.
Surgical options for thyroid cancer include thyroid lobectomy, subtotal thyroidectomy [removal of most of the visible thyroid tissue, preserving only a small amount of tissue attached around the site where the recurrent laryngeal nerve enters the cricothyroid muscle (about 1 g) and total thyroidectomy (removal of all visible thyroid tissue). Subtotal thyroidectomy with preservation of the posterior thyroid tissue (>1g) on the side of the lesion is not suitable for the treatment of thyroid cancer.
Sub-total or total thyroidectomy is recommended if
①Tumor diameter >1cm;
②There is a thyroid nodule on the opposite side of the tumor;
③there is local or distal metastasis;
④Patients with history of head and neck radiotherapy;
⑤ A history of differentiated thyroid cancer in the first-degree relative of the patient. Patients who are older (>45 years old) have a higher recurrence rate, and the above procedure is also recommended.
Local lymph node metastasis is present in 20% to 90% of patients with papillary thyroid cancer at the time of diagnosis, while the metastasis rate is lower in patients with other types of tumors. Bilateral central (zone VI) lymph node dissection may improve survival and reduce the rate of lymph node recurrence. Total thyroidectomy should be performed when the thyroid lobe is removed due to an undiagnosed diagnosis or when a non-diagnostic biopsy confirms a malignant lesion. Total thyroidectomy should be performed in patients with multiple thyroid cancers to ensure complete removal of the lesion and to prepare for I131 radiotherapy.
American Joint Committee on Cancer (AJCC)/International Union Against Cancer (UICC) TNM Staging
Postoperative staging of thyroid cancer can be used to.
① Determine the individual prognosis of patients with differentiated thyroid cancer;
(ii) guide postoperative adjuvant therapy, including I131 radiotherapy and TSH suppressive therapy, to reduce the recurrence rate and mortality of patients;
(iii) To determine the timing and frequency of follow-up visits and to provide more intensive follow-up for high-risk patients;
④Help patients communicate better with their physicians.
The AJCC/UICC classification system based on TNM parameters is applicable to all types of tumors, including thyroid cancer, because it provides an effective and convenient way to describe the extent of tumors. This classification scheme takes into account a number of predictors of regression, the most meaningful of which are the presence of distant metastases, patient age and tumor extent.
Long-term follow-up of differentiated thyroid cancer
The goal of long-term follow-up of patients with differentiated thyroid cancer is to closely monitor patients with possible recurrence in order to detect recurrent lesions as early as possible, and early detection of recurrent lesions can help in the effective treatment of patients. The content of follow-up varies depending on the persistence of the lesion or the risk of recurrence. The American Joint Committee on Cancer (AJCC)/International Union Against Cancer (UICC) TNM staging predicts the risk of death but not the risk of tumor recurrence.
To assess patient prognosis and determine treatment options, patients should be classified into 3 levels according to the risk of recurrence.
Low-risk patients.
No local or distant metastases after initial surgical treatment and removal of residual lesions, all visually visible tumors have been removed, the tumor has not invaded local tissues and there are no highly invasive pathological manifestations or invasive vessels. If I131 is used, then there is no I131 uptake outside the thyroid bed when a whole body radioiodine scan (RxWBS) is performed after the initial surgery.
Intermediate risk patients.
Tumor invasion into parathyroid soft tissue visible to the naked eye at the time of initial surgery, or tumor with invasive pathologic manifestations or invasion of blood vessels.
High-risk patients.
Tumor invasion into peripheral tissues visible to the naked eye at the time of initial surgery, incomplete tumor resection, distant metastases, or iodine uptake outside the thyroid bed visible on I131 scan after removal of residual thyroid lesions. Patients who have undergone total or near-total thyroidectomy are considered disease-free if all of the following conditions are present: no clinical evidence of the presence of a tumor, no imaging evidence of the presence of a tumor (no iodine uptake outside the thyroid bed on postoperative whole-body scans, on recent diagnostic scans, and on neck ultrasound), and in the absence of interfering antibodies, no iodine uptake during suppression and stimulation with TSH. Thyroglobulin (Tg) was detected.