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Suppressive therapy with levothyroxine :
– It is believed that the growth of benign tumors and some forms of differentiated thyroid cancer depends on TSH . Thus, tumor regression can be achieved by maintaining a TSH level at the lower limit of normal. Some endocrinologists suggest the use of suppressive therapy with thyroid hormones at the initial stage of treatment of any thyroid gland nodes. If the size of the node against the background of suppressive therapy does not decrease, a malignant tumor should be suspected and treated surgically.
– Usually, in order to suppress TSH secretion in patients with thyroid gland nodes, somewhat higher doses of thyroid hormones are used than with hypothyroidism replacement therapy .
– The duration of suppressive therapy is at least 3 months. Treatment is considered successful if the size of the tumor has decreased by 2 times or more. If by the end of the 3rd month the size of the node decreases by less than 50% or does not decrease or increase, it is recommended to remove the node. If the node decreases by more than 50%, treatment with levothyroxine is continued.
– The dimensions of the node are estimated by a ruler or using ultrasound. The completeness of suppression of TSH secretion is evaluated by determining the levels of T4 and TSH. A reliable indicator of the complete suppression of TSH secretion is the absence of an increase in TSH concentration in the stimulation sample with thyroliberin .
Surgery:
– Indications: the node with ultrasound is solid , on the scintigram – cold ; the anamnesis and the results of a physical examination make us suspect a malignant tumor. Especially alarming are the following symptoms: radiation of the thyroid gland or radiation therapy of non-thyroid diseases in early childhood, the young age of the patient (less than 20 years), and recently begun or rapid growth of the node.
– The question of the need for a biopsy. Many endocrinologists conduct an aspiration biopsy of the node before surgery to verify its malignancy. It is often recommended to remove most solid cold and many hot nodes in young children without a preliminary aspiration biopsy (since it often requires general anesthesia to conduct it).
– Determining the scope of the operation. Arguments in favor of thyroidectomy or subtotal resection: after hemithyroidectomy and isthmus resection in 87.5% of patients, microscopic foci of cancer are found in the contralateral lobe of the gland; almost 10% of patients after hemithyroidectomy and resection of the isthmus in the remaining lobe of the gland have cancer, which manifests itself clinically; after thyroidectomy or subtotal resection, it is easier to detect thyroid cancer metastases by means of panoramic scintigraphy with radioactive iodine.
– An increase in the level of thyroglobulin in serum after thyroidectomy serves as a marker of metastases of differentiated thyroid cancer (since in the absence of metastases after thyroidectomy, thyroglobulin practically disappears from serum).
The need for lymphadenectomy. The risk of thyroid cancer recurrence and the survival of patients depend little on the completeness of lymph node removal. Any suspicious lymph node should be removed, but cervical lymphadenectomy is not indicated, since it does not give any advantages compared to thyroidectomy with excision of individual lymph nodes.
Postoperative Maintenance:
– Levothyroxine orally in doses of 125 μg / m squared per day is prescribed to suppress TSH secretion (i.e., to prevent relapse of TSH-dependent tumor ), as well as for the prevention of hypothyroidism . The maximum suppressive effect of levothyroxine is confirmed by the absence of an increase in TSH concentration in the stimulation test with thyroliberin or by the results of TSH determination by highly sensitive methods.
– To detect metastases (especially in the lungs), scintigraphy (185-370 MBq) is performed 4-6 weeks after surgery. A study by A. Winship et al. Showed that lung metastases in the early stages after thyroidectomy are found in 14.4% of children; in 5.2% of children, they appear after a few years. Chest x-ray is a less reliable way to detect lung metastases. According to observations, in some children with lung metastases detected by scintigraphy, these metastases were not detected by x-ray. If a large amount of normal tissue is preserved in the thyroid gland, then metastases may not be detected during scintigraphy (since normal thyrocytes capture much more actively than tumor cells ). Tumor cell uptake can be enhanced by increasing serum TSH levels. For this, 4 weeks before scintigraphy, levothyroxine is replaced with lyothyronine ; 25 mcg of lyothyronine is equivalent to 100 mcg of levothyroxine. Lyiotironin is given 2 times a day for 2 weeks; 2 weeks before scintigraphy, it is canceled. Before administration, the TSH level should increase to about 50 mU / L.
– TSH levels can be increased by canceling levothyroxine 4-6 weeks before scintigraphy. Some endocrinologists recommend the administration of thyrotropin (10 units / day, IM for 3 days) to stimulate absorption, but sometimes patients are allergic to thyrotropin.
– Regularly determine the content of thyroglobulin in serum. If there is no residual normal and tumor tissue, the level of thyroglobulin does not exceed 10 ng / ml. A high thyroglobulin level indicates the presence of tumor tissue (even if it is not detected by scintigraphy). It was shown that scintigraphy reveals residual tissue or recurrent tumor growth in the thyroid gland bed and in the neck structures better than the determination of thyroglobulin in serum. On the contrary, the determination of thyroglobulin is more informative in identifying distant metastases. Attention: if a patient with thyroid cancer has autoantibodies to thyroglobulin , the determination of thyroglobulin gives false negative results.
– Destruction of remaining thyroid tissue with help. While retaining the residual thyroid tissue, but in the absence of metastases, a destructive amount (1.1-1.85 GBq) is administered and scintigraphy is performed with an interval of 1 week to check if metastases have appeared. If metastases appear, they are administered in an amount of 3.7-5.55 GBq. If necessary, the treatment is repeated at 6-12-month intervals, but not earlier than when the bone marrow is completely restored after the previous dose. In rare cases, patients receiving large quantities at short intervals have leukemia .
– With combined treatment with levothyroxine, the risk of cancer recurrence is lower than with treatment with only one of these methods.
– In rare cases, after treatment or after scintigraphy with pulmonary fibrosis develops . If at the first scintigraphy survey residual thyroid tissue and removed metastases are not detected, scintigraphy is repeated after 3-5 years.