Medullary Thyroid Carcinoma

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Recommended surgical treatment of MTC is influenced by several factors. First, the clinical course of MTC is usually more aggressive than that of differentiated thyroid cancer, with higher recurrence and mortality rates. Second, MTC cells do not take up radioactive iodine, and radiation therapy and chemotherapy are ineffective. Third, MTC is multicentric in 90% of patients with the hereditary forms of the disease. Fourth, in patients with palpable disease, over 70% have nodal metastases. Lastly, the ability to measure postoperative stimulated calcitonin levels has allowed assessment of the adequacy of surgical extirpation. Screening for pheochromocytoma should be done before performing thyroid surgery. If patients are found to have evidence of pheochromo-cytoma, adrenal surgery with perioperative alphablockade should precede other procedures.

Preventive thyroidectomy is recommended before age 6 years in patients with MEN type IIA and FMTC. Patients with MEN type IIB should undergo thyroidectomy during infancy because of the aggressiveness and earlier age of onset of MTC in these patients. These procedures are best performed by surgeons experienced in thyroid surgery in children as finding the parathyroids can be extremely difficult owing to their small size and translucent appearance.

Thorough surgical extirpation is the only curative treatment for MTC. In patients without a palpable neck mass who are found to be carriers of a RET mutation by genetic testing, total thyroidectomy and central node dissection are recommended. At our institution, total parathyroidectomy with autotransplantation is often done at the same time as total thy-roidectomy for MTC. This is because the parathyroid glands are closely associated with perithyroidal lymph nodes and preservation of these glands is difficult if the central nodes are removed. The vascular supply to a parathyroid gland may be interrupted by dissection and excision of perithyroidal and central nodes. Parathyroid glands are therefore removed and preserved in cold saline at the time of thyroidectomy for MTC. The glands are sliced into 20 1 x 3 mm fragments and autotransplanted into the muscle of the nondominant forearm (in patients with MEN type IIA) or sternocleidomastoid muscle (in patients with FMTC or MEN type IIB). Patients are maintained on calcium and vitamin D supplementation for 4 to 8 weeks postoperatively. In a recent series of thyroidectomies performed in 13 patients with hereditary MTC identified by genetic screening, total thyroidectomy and central node dissection with parathyroidectomy and parathyroid autografting were performed in all patients. All patients were nor-mocalcemic after stopping calcium supplementation 8 weeks postoperatively.12 In other series, the percentage of patients requiring calcium supplementation following parathyroidectomy with parathyroid autografting has ranged from 0 to 18%.15 Other experts in this field attempt to preserve the glands with vascular supply intact during thyroidectomy for MTC. Parathyroidectomy with autotransplantation should be done in all patients with gross parathyroid enlargement or biochemical evidence of parathyroid disease at the time of operation for MTC.

In patients who present with palpable thyroid masses, the risk of more extensive nodal metastatic disease is increased. In the past, authors have rec ommended total thyroidectomy with node dissections only if nodes are clinically palpable. This is an effective strategy for differentiated thyroid cancer, for which suppression with thyroxine and radioactive iodine ablation are extremely effective adjuncts to surgery, but MTC cells do not respond to these nonsurgical treatments. Surgery is the only effective therapeutic modality for MTC at the present time. Overall, persistent disease, evidenced by elevation of calcitonin levels, is present in over 50% of patients following surgery for MTC. In the absence of effective adjuvant therapy, there is a need to better define or predict the extent of spread of these tumors at the time of diagnosis so that appropriate operative resection can be performed.

There is a high incidence of metastatic disease in central and bilateral level II to V lymph nodes in patients with palpable tumors. Based on these results, our recommendation for patients who present with palpable MTC is total thyroidectomy, parathyroidec-tomy with autotransplantation, central neck dissection (right and left levels VI and VII), and ipsilateral or bilateral level II to V node dissections, depending on the extent of nodal involvement apparent at operation. The central node dissection encompasses all tissue from the level of the hyoid bone superiorly to the innominate vessels inferiorly and laterally to the carotid sheaths (Figure 17-9). Nodal tissue on the

Figure 17-9. Total thyroidectomy and central (levels VI and VII) and bilateral level II to V node dissections from a thin young male with multiple endocrine neoplasia type IIA and bilateral palpable thyroid masses (parathyroids not shown). Microscopic metastases were present in all nodal groups. Reproduced with permission from Moley JF, Lairmore TC, Phay JE. Hereditary endocrinopathies. Curr Probl Surg 1999;36:653-764.

Figure 17-9. Total thyroidectomy and central (levels VI and VII) and bilateral level II to V node dissections from a thin young male with multiple endocrine neoplasia type IIA and bilateral palpable thyroid masses (parathyroids not shown). Microscopic metastases were present in all nodal groups. Reproduced with permission from Moley JF, Lairmore TC, Phay JE. Hereditary endocrinopathies. Curr Probl Surg 1999;36:653-764.

anterior surface of the trachea is removed, exposing the superior surface of the innominate vein behind the sternal notch. Fatty and nodal tissue between the carotid artery and the trachea is removed, including paratracheal nodes along the recurrent nerves. On the right, the junction of the innominate and right carotid arteries is exposed, and on the left, nodal tissue is removed to a comparable level behind the head of the left clavicle. A systematic approach to the removal of all nodal tissue in these patients has been reported to improve recurrence and survival rates when compared retrospectively with procedures in which only grossly involved nodes were removed.19

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