Thyroid Cancer Treatment (Professional) (cont.)
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Medullary Thyroid Cancer
Medullary thyroid cancer (MTC) comprises 3% to 4% of all thyroid cancers. These tumors usually present as a mass in the neck or thyroid, often associated with lymphadenopathy, or they may be diagnosed through screening family members. MTC can also be diagnosed by fine-needle aspiration biopsy. Cytology typically reveals hypercellular tumors with spindle-shaped cells and poor adhesion.
The overall survival of patients with MTC is 86% at 5 years and 65% at 10 years. Poor prognostic factors include advanced age, advanced stage, prior neck surgery, and associated multiple endocrine neoplasia (MEN) 2B.[2,3,4]
Approximately 25% of reported cases of MTC are familial. Familial MTC syndromes include MEN 2A, which is the most common; MEN 2B; and familial non-MEN syndromes. (Refer to the PDQ summary on Genetics of Endocrine and Neuroendocrine Neoplasias for more information.) Any patient with a familial variant should be screened for other associated endocrine tumors, particularly parathyroid hyperplasia and pheochromocytoma. MTC can secrete calcitonin and other peptide substances. Determining the level of calcitonin is useful for diagnostic purposes and for following the results of treatment.
Family members should be screened for calcitonin elevation and/or for the RET proto-oncogene mutation to identify other individuals at risk for developing familial MTC. All patients with MTC (whether familial or sporadic) should be tested for RET mutations, and if they are positive, family members should also be tested. Whereas modest elevation of calcitonin may lead to a false-positive diagnosis of medullary carcinoma, DNA testing for the RET mutation is the optimal approach. Family members who are gene carriers should undergo prophylactic thyroidectomy at an early age.[5,6]
Treatment options for localized disease:
Patients with MTC should be treated with a total thyroidectomy, unless there is evidence of distant metastasis. In patients with clinically palpable MTC, the incidence of microscopically positive nodes is more than 75%; routine central and bilateral modified neck dissections have been recommended. When cancer is confined to the thyroid gland, the prognosis is excellent.
External Radiation Therapy
External radiation therapy has been used for palliation of locally recurrent tumors; however, no evidence exists that it provides any survival advantage. Radioactive iodine has no place in the treatment of patients with MTC.
Treatment options for locally advanced and metastatic disease:
Vandetanib is an oral inhibitor of RET kinase, vascular endothelial growth-factor receptor, and epidermal growth-factor receptor signaling. It was tested in a placebo-controlled, prospective trial (NCT00410761) in 331 patients with locally advanced and metastatic disease with a 2:1 ratio in assignment to the study drug. With a median follow-up of 24 months, progression-free survival (PFS) favored vandetanib (hazard ratio = 0.46; 95% confidence interval, 0.31–0.69; P < .001) with a median PFS estimated at 30.5 months for vandetanib versus 19.3 months for placebo.[Level of evidence: 1iiDiii]
Overall survival (OS) was not different at 24 months; longer follow-up will be required since only 47 patients had died at the time of analysis, and there was a crossover to the study drug on progression from placebo, making analysis of OS problematic. Vandetanib has significant side effects, including diarrhea, rash, hypertension, and QT prolongation. Quality of life was not formally assessed in this trial.
Palliative chemotherapy has been reported to produce occasional responses in patients with metastatic disease.[10,11,12,13] No single drug regimen can be considered standard. Some patients with distant metastases will experience prolonged survival and can be managed expectantly until they become symptomatic.
Current Clinical Trials
Check for U.S. clinical trials from NCI's list of cancer clinical trials that are now accepting patients with thyroid gland medullary carcinoma. The list of clinical trials can be further narrowed by location, drug, intervention, and other criteria.
General information about clinical trials is also available from the NCI Web site.
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