First-line treatment for thyroid cancer is surgery. The procedure performed is usually a total thyroidectomy, where the entire thyroid is removed, or a subtotal thyroidectomy, where nearly the entire thyroid is removed except for a small amount of tissue. During surgery, the lymph nodes are examined and may be removed if cancerous. In medullary thyroid cancer, in addition to total thyroidectomy, a central neck dissection (removal of all lymph nodes and fatty tissues in the central neck area) is usually performed.
In many cases of well-differentiated, localized thyroid cancer, thyroidectomy affords an excellent chance of cure or long-term survival. It should be noted that radioiodine therapy (discussed below) is usually given to destroy any residual thyroid cancer cells that may remain after thyroidectomy.
Regular follow-up visits, which will include diagnostic scans, are important to detect any recurrence.
Radioiodine therapy destroys residual thyroid cancer cells that may be present after surgical removal of the thyroid. This is important because such residual cells are common in many cases of thyroid cancer. Radioiodine therapy also destroys noncancerous thyroid tissue, creating what is known as an athyroidal state. Destroying even noncancerous residual thyroid tissue is helpful because residual tissue will take up radioiodine in a scan, making it more difficult to visualize thyroid cancer sites during follow-up imaging scans. Residual thyroid tissue also produces thyroglobulin, so the use of thyroglobulin as a tumor marker in follow-up is less valuable.
Radioiodine therapy can cause side effects such as sore throat, nausea, vomiting and dry mouth. Depending on the amount of radiation to be administered, isolation may be necessary to protect family and friends from exposure.
Thyroid Hormone Replacement
Because radioiodine therapy destroys thyroid tissue, there is no mechanism for the body to produce thyroid hormone (thyroxine), which is essential. Thyroxine is prescribed and must be taken daily. Not only does this prevent hypothyroidism, it also suppresses thyroid stimulating hormone (TSH) levels. Suppression of TSH is thought to reduce the chance of thyroid tumor growth.
Preparing for Radioiodine Therapy or Follow-up Radioiodine Scan
In order to obtain optimal results (high radioiodine uptake) from your radioiodine therapy, you need to have high blood levels of TSH. This normally would entail stopping daily thyroxine therapy for a period of time. Unfortunately, the hypothyroid state this induces is uncomfortable. Until recently, this was the only practical way to raise TSH in preparation for a scan.
Today, another option is available. Thyrogen, a brand of recombinant TSH, can now be administered to patients to raise their TSH levels in preparation for their radioiodine scans or radiotherapy. Patients can continue their normal daily thyroxine therapy throughout the process.
External Beam Radiation Therapy
In thyroid cancers that do not take up radioiodine, and in advanced cases where surgery is not an option, or in recurrent thyroid cancers, external beam radiation therapy may be used. Here, an external source of radiation (a machine) is used to deliver radioactivity to the thyroid. A high dose of radiation is employed to destroy thyroid cancer cells.
Patients may experience side effects such as sore throat, hoarseness, difficulty in swallowing and dry mouth.
Chemotherapy is used in thyroid cancers that have metastasized and/or thyroid cancers that do not respond to radioiodine therapy. Usually a combination of drugs is administered.
New Approaches in Chemotherapy
The more troublesome and aggressive types of thyroid cancer are poorly differentiated or undifferentiated. Because they cannot take up radioiodine, a very powerful therapeutic modality is therefore unavailable. A novel strategy, called redifferentiation, has been under investigation recently, and shows significant promise. The premise of this approach is that certain compounds can redifferentiate the poorly-differentiated cells, making them now able to concentrate radioiodine.
Radioimmunotherapy has produced encouraging results in medullary thyroid cancer. Because this type of thyroid cancer produces carcinoembryonic antigen (CEA), the cancer cells can be targeted using a radiolabeled antibody called anti-CEA.
City of Hope has several clinical trials involving experimental therapies for advanced solid tumors, including thyroid cancer. Click here for more information.