In 2011, the American
Cancer Society estimated that 48,020 new cases of thyroid cancer will be
diagnosed in the United States (36,550 in women and 11,470 in men)
CLASSIFICATION of
Follicular Thyroid Cancer:
Thyroid follicular
epithelial-derived cancers are divided into three categories:
-Papillary cancer
-Follicular cancer
-Anaplastic cancer
Papillary and follicular cancers are considered differentiated
cancers and patients with these tumors are often treated similarly despite
numerous biologic differences. Most anaplastic (undifferentiated) cancers
appear to arise from differentiated cancers.
TREATMENT of Follicular
Thyroid Cancer
Once
the diagnosis of differentiated thyroid cancer is established, several
treatment options may be considered, depending upon the extent of the disease,
the patient's age, and the presence of comorbid conditions.
Surgery — Surgery is the primary mode of
therapy for patients with differentiated thyroid cancer. We recommend total
thyroidectomy if the primary tumor is at least 1.0 to 2.0 cm in diameter, or if
extrathyroidal extension or metastases are present. This operation should be
performed by an experienced thyroid surgeon to minimize the risk of
hypoparathyroidism and recurrent laryngeal nerve injury.
Radioiodine therapy — Radioiodine
is the most effective adjuvant treatment for papillary thyroid cancer, in the
form of 131-iodine (131-I). Radioiodine causes cytotoxicity by the emission of
short path-length (1 to 2 mm) beta radiation. Radioiodine uptake is dependent
upon adequate stimulation by TSH, and is reduced by the presence of excess
stable iodide. Therefore, whenever radioiodine imaging and treatment are
planned, the patient should be instructed to avoid all iodine-containing
medications and to limit dietary intake of iodine for at least one week. In
addition, the intravenous contrast used for CT scans contains a large iodine
load and may interfere with RAI scanning and therapy for several months.
Thyroid hormone suppression — After
initial surgery, whether or not radioiodine therapy is administered, we suggestlevothyroxine therapy for all patients to prevent hypothyroidism
and to minimize potential TSH stimulation of tumor growth.
Medullary Thyroid
Cancer:
Medullary
thyroid cancer (MTC) is a neuroendocrine tumor of the parafollicular or C cells
of the thyroid gland. MTC accounts for approximately four percent of thyroid
carcinomas. A characteristic feature of this tumor is the production of
calcitonin. In addition, the C cells originate from the embryonic neural crest;
as a result, medullary carcinomas often have the clinical and histologic
features of other neuroendocrine tumors such as carcinoid and islet-cell tumors.
Genetic screening in sporadic Medullary Thyroid Cancer (MTC) — Some patients with apparently sporadic MTC have
unsuspected germline RET mutations (the underlying defect in MEN2) and,
therefore, heritable disease. We therefore agree with the 2009 American Thyroid
Association Guidelines for Management of Medullary Thyroid Cancer that all
patients with C cell hyperplasia or MTC be offered germline RET testing
Staging of Thyroid Cancer:
STAGING — The pTNM criteria for
clinicopathologic tumor staging adopted by The Union International Contre le
Cancer (UICC) and the American Joint Committee on Cancer (AJCC) are based upon
tumor size and the presence or absence of extrathyroidal invasion, local and
regional nodal metastases, and distant metastases:
Stage I — MTCs that are less
than 2 cm in diameter without evidence of disease outside of the thyroid
gland
Stage II — any tumor between 2
and 4 cm without evidence of extrathyroidal disease
Stage III — any tumor greater
than 4 cm, or level VI nodal metastases or microscopic extrathyroidal
invasion regardless of tumor size
Stage IV — any distant
metastases, or lymph node involvement outside of level VI, or gross soft
tissue extension
SURGICAL THERAPY — Total
thyroidectomy is the preferred initial treatment for patients with MTC. Up to
30 percent of patients with sporadic MTC and all patients with inherited MTC
have bilateral or multifocal disease
Here, Dr. Tony Talebi discusses the general
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endocrinology at the University of Miami and co-leader of thyroid disease
group. The discussion includes Thyroid
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for thyroid cancer.
Dr. Brian Kim’s credentials:
Certifications
·American Board of Internal Medicine-Endocrinology
Diabetes & Metabolism
Specialties
·Endocrinology, Diabetes and
Metabolism
·Internal Medicine
Roles
·Assistant Professor
·Co-Leader, Thyroid Cancer Site
Disease Group
Biography
Brian W. Kim, MD, was educated at
Harvard College and received his M.D. from the College of Physicians and
Surgeons at Columbia University. He did his endocrinology fellowship at
Brigham and Women's Hospital in Boston, and subsequently joined the faculty of
Harvard Medical School in 2004. Dr. Kim relocated to the University of
Miami in early 2009, where he has established a research lab studying the
mechanisms underlying thyroid hormone's effects on energy expenditure.
His clinical interests focus on thyroid disease, with an emphasis on the
treatment of thyroid cancer.
