Initial Treatment

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An early diagnosis and complete surgical treatment are the bases for a definitive cure of patients affected by medullary thyroid carcinoma (Figure 21.16). The minimal standard procedure is total (or near-total) thyroidectomy with central neck lymph node dissection, in both sporadic and familial forms. The need for total thyroidectomy is supported by the multi-centricity and bilaterality of the medullary thyroid carcinoma that occurs in about 100% of the hereditary form and 30% of sporadic form [22]. Furthermore, C-cell hyperplasia, which is considered a preneoplastic lesion, is almost invariably associated with the hereditary form of medullary thyroid carcinoma and, to a lesser extent, with the sporadic form [24]. An additional reason in favor of total thyroidectomy is the fact that, as mentioned above, 5-7% of apparently sporadic cases are in fact hereditary forms, which almost invariably have bilateral disease [20,21].

Central node dissection, from the hyoid bone to the innominate veins, is mandatory during the initial operation. This node compartment is in fact the primary lymphatic drainage of the thyroid and 50-60% of medullary thyroid carcinomas show node metastases in this area at the time of presentation [51,141]. The removal of the central compartment also has a prophylactic significance and must be performed independently of the size of the primary tumor and the presurgical evidence of lymph node involvement. This surgical approach is also suggested in RET gene carriers without clinical evidence of the disease, which can be completely cured by surgical treatment. It is still controversial as to whether the central node dissection has to be performed in child gene carriers without clinical and biochemical (undetectable levels of basal and stimulated calcitonin) evidence of disease [142-144].

Whenever a presurgical clinical diagnosis of node metastases is achieved, the surgical dissection of the corresponding lateral node compartment should be included. It is still debated whether a modified radical neck dissection with removal of nodes in the ipsilateral or bilateral compartment should be performed in any case. Since unilateral or bilateral cervical nodal metastases occur in up to 90% of patients with medullary thyroid carcinoma, especially when

Years of follow-up

Figure 21.16 Different survival rates of patients affected by MTC according to the tumor extension at the time of the diagnosis: The best prognosis is observed in patients with MTC at stage I. (Modified from Gharib et al. [15].)

Years of follow-up

Figure 21.16 Different survival rates of patients affected by MTC according to the tumor extension at the time of the diagnosis: The best prognosis is observed in patients with MTC at stage I. (Modified from Gharib et al. [15].)

the primary tumor is palpable [39,55], several authors strongly suggest an "en bloc" dissection of both central and bilateral neck compartments together with the thyroid gland [145]. This is of great clinical significance because the adequacy of the initial surgical treatment is a prerequisite for the effective cure of the MTC, thus the choice of the most appropriate initial procedure is fundamental. In this regard it is worth considering that radical neck dissection may result in significant morbidity and has not been clearly shown to improve the prognosis of the disease, which in fact is dependent on several other factors such as the local extent of the disease at the time of diagnosis, the presence or absence of other endocrine neoplasia, and, the presence of cervical lymph node metastases. Patients who are cured by the initial treatment are usually those with a lower stage of disease, with no involvement of lateral nodes in the neck. Several reports indicate that when lateral node metastases are present at diagnosis, achievement of a definitive cure with the initial treatment is uncommon regardless of the extent of the surgical procedure [67,146,147].

C cells are not able to actively concentrate radioiodine and, as consequence, 131I radioactive ablation is not useful in medullary thyroid carcinoma. There are only a few anecdotal reports indicating a beneficial effect of 131I treatment of the postsurgical remnant presumably due to death of C cells adjacent to follicular cells as consequence of a bystander effect [148,149].

In patients with a locally aggressive disease not completely removed by the primary resection, surgical treatment should be followed by external-beam radiotherapy as adjuvant treatment. Although bulky medullary thyroid carcinoma deposits are consistently resistant to external radiotherapy, there is evidence of a potential benefit from radiotherapy in terms of a lower risk (from two- to fourfold) of local recurrence in patients with residual disease [150,151].This procedure should be reserved for patients who have undergone complete central compartment and lateral neck dissection and postponed to a second surgical treatment in those who have been approached with a less aggressive primary resection. Radiation therapy after thyroidectomy and node dissection is not generally recommended on a prophylactic basis but it is worth mentioning that there is some evidence that external beam radiation in patients with residual malignant disease after surgery may increase the 5-year survival rate from 60% to 95% [152].

Hormone replacement therapy with L-thyroxine (L-T4) should be started immediately after thyroidectomy. Unlike papillary and follicular thyroid tumors, medullary carcinoma is not dependent on TSH for both growth and function, thus there is no need to treat patients with L-T4 suppressive therapy: the daily dose should be tailored by measuring serum FT3, FT4, and TSH aiming to keep their values within the normal range. Unilateral or bilateral adrenalec-tomy must be performed before total thyroidec-tomy, when a pheochromocytoma has been documented, because of the risk of a life-threatening hypertensive crisis during the induction of anesthesia for the neck surgical treatment. Preoperative screening for pheochro-mocytoma should be conducted in all patients with a diagnosis of medullary thyroid carcinoma since the patient may be an index case of a familial form, presented as apparently sporadic. Although pheochromocytoma is usually bilateral, a 10-year interval is the mean period between the first and the contralateral adrenal mass appearance. Different approaches to the management of adrenal medullary disease are suggested when only one adrenal gland is involved at the time of the diagnosis. Bilateral adrenalectomy in principle eliminates the need for a second intervention later in the patient's life, but implies the risk associated with the cor-ticosteroid deficiency. Since a laparoscopic surgical approach has been introduced [153], the preferred strategy is to remove only the affected adrenal gland and periodically monitor the morphology and function of the other adrenal gland. Whatever the final decision, all patients to be submitted to adrenalectomy should be treated preoperatively with pharmacological a-and b-adrenergic antagonists [154,155].

Grossly enlarged parathyroid glands should be resected during the first operation for patients with hereditary forms of medullary thyroid carcinoma and documented clinical hyperparathyroidism. An intraoperative serum parathyroid hormone measurement is recommended to ensure the precise and total removal of the affected gland(s). This procedure is of practical importance especially when the macroscopic appearance of the removed parathyroid is not indicative of the presence of adenoma, suggesting the presence of multiple adenomatosis or diffuse hyperplasia [156]. In some centers normal or hyperplastic parathyroid glands of patients with hereditary forms are always removed, even in the presence of normal serum parathyroid hormone levels. They are appropriately marked, for making their localization easier whenever it might be necessary, and totally or partially implanted in a muscle [157]. It is worth noting that an aggressive management of normal parathyroid glands is associated with a higher incidence of hypoparathyroidism. In this regard, a greater concern is represented by young RET gene carriers who, if rendered hypoparathyroid, would be exposed to the need for calcium and vitamin D supplementation for the rest of their lives.

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