Medullary thyroid cancer (MTC) is a neoplasm of the thyroid that is rare and can occur in a sporadic form or in a hereditary form. It derives from neuroendocrine parafollicular or calcitonin cells. Approximately 75% of cases are sporadic. The remainder are hereditary owing to germline mutations activating the Rearranged during Transfection (RET) proto-oncogene. The hereditary form occur in multiple endocrine neoplasia type 2 (MEN2). These have district phenotypes resulting from a different RET gent mutation.
Although medullary thyroid cancer accounts represents 3% of all thyroid cancer, but is responsible for 14% of thyroid cancer–related deaths. MTC has a lower 10-year relative survival risk compared with patients with papillary and follicular carcinoma. When lymph nodes are involved, the prognosis decreases further.
We currently treat MTC by complete surgical excision, which includes at minimum a total thyroidectomy and central compartment neck dissection but may include varying levels of lateral neck dissection, depending on the patient presents.
In papillary thyroid cancer, radioactive iodine is utilized. For MTC, Radioactive iodine I-131 is not used. The parafollicular calcitonin cells do not actively take up iodine therefore treatment with radioactive iodine would be not effective. External beam radiation also is not helpful in this cancer. In fact it has been shown to be an independent predictor of decreased survival.
There are several identified predictors of survival for MTC. These include female sex, young age at the time of diagnosis, localized stage, well- or moderately differentiated histologic features, and absence of cervical lymph node involvement.
Oncologic drugs to treat MTC are limited. Vandetenib and Lenvatinib are approved kinase inhibitors for MTC that cannot be removed by surgery and is locally advanced or has metastasized.
After surgery, patients who have had MTC should be assessed regularly for presence of residual disease, localization of metastasis, and identification of progressive disease. Postoperative calcitonin and carcinoembryonic antigen levels should be monitored. If the postoperative calcitonin level exceeds 150 pg/ml, consider imaging such as computed tomography of the neck and chew, contrast enhanced magnetic resonance imaging (MRI), and ultrasound of the liver, bone scintigraphy, MRI of the bone, and positron emission tomography. Considering that metastatic MTC is not curable, management goals become priority. These include control of loco regional disease, palliate symptoms of hormonal excess (diarrhea), symptomatic metastases (bone pain, fracture), and life threatening bronchial obstruction or spinal cord compression.
Presented to you by Dr. Philip Harris
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