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Cancer of the Thyroid |
Thyroid cancer is
the most common endocrine-related cancer; however, it is rare compared
to other cancers. In the United States there are only about 20,000
new patients annually. Even though the diagnosis of cancer is terrifying,
the outlook for patients with thyroid cancer is usually excellent.
First, most thyroid cancer is easily curable with surgery. Second,
thyroid cancer rarely causes pain or disability. Third, effective
and well-tolerated treatment is available for the most common forms
of thyroid cancer. |
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SYMPTOMS |
What
are the symptoms of thyroid cancer? |
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2 |
CAUSES |
What
causes thyroid cancer? Exposure of the thyroid to radiation causes thyroid cancer in susceptible patients, especially if the exposure occurred as a child. Many years ago (ie, in the 1940s and 1950s), radiation exposure included X-ray treatments for acne, inflamed tonsils, adenoids, lymph nodes, or an enlarged thymus gland. X-rays also were used to measure foot sizes in shoe stores. Currently, X-ray exposure is usually limited to treatment of serious cancers such as Hodgkin’s disease (cancer of the lymph nodes). Routine X-ray exposure (eg, dental X-rays, chest X-rays, mammograms) does not cause thyroid cancer. Thyroid cancer can be caused by absorbing radioactive iodine released during a nuclear power plant emergency, such as the 1986 nuclear accident at the Chernobyl power plant in Russia. Children who were exposed were the most affected, and cancers were seen within a few years of that disaster. You can be protected from developing thyroid cancer due to a nuclear power plant emergency by taking potassium iodide, which blocks your thyroid from absorbing radioactive iodine. The United States government is currently developing guidelines to distribute potassium iodide to people living near nuclear power plants. |
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3 |
DIAGNOSIS |
How is thyroid cancer
diagnosed? What are the types of thyroid cancer?
Follicular thyroid cancer. Follicular thyroid cancer, which makes up about 10% to 15% of all thyroid cancers in the United States, tends to occur in somewhat older patients than does papillary cancer. As with papillary cancer, follicular cancer first can grow into lymph nodes in the neck. Follicular cancer is also more likely than papillary cancer to grow into blood vessels and from there to spread to distant areas, particularly the lungs and bones. Medullary thyroid cancer. Medullary thyroid cancer, which accounts for 5% to 10% of all thyroid cancers, is more likely to run in families and be associated with other endocrine problems. In fact, medullary thyroid cancer is the only thyroid cancer that can be diagnosed by genetic testing of the blood cells. In family members of an affected person, a positive test for the RET proto-oncogene can lead to an early diagnosis of medullary thyroid cancer and, subsequently, curative surgery to remove it. Anaplastic thyroid cancer. Anaplastic thyroid cancer is the most advanced and aggressive thyroid cancer and is the least likely to respond to treatment. Fortunately, anaplastic thyroid cancer is rare and found in less than 5% of patients with thyroid cancer. |
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4 |
TREATMENT |
What
is the treatment for thyroid cancer? Radioactive iodine therapy. A major reason for the usually excellent prognosis for patients with papillary and follicular thyroid cancer is that radioactive iodine can be used as a magic bullet to seek out and destroy thyroid cancer cells with little or no damage to other tissues in the body. Thyroid cells normally concentrate iodine from the bloodstream to use to produce the thyroid hormones. By contrast, thyroid cancer cells usually take up only tiny amounts of iodine. However, high levels of thyroid stimulating hormone (TSH) can arouse thyroid cancer cells to take up significant amounts of iodine. If your doctor recommends radioactive iodine therapy, high levels of TSH will be produced in your body by making you hypothyroid for a short time—either by not starting thyroid hormone pills after the thyroid gland is removed or by stopping your thyroid hormone pills if you are already on medication. Sometimes, to minimize your symptoms of hypothyroidism, your doctor may prescribe Cytomel™ (T3) to take while you are becoming hypothyroid. Also, you may be asked to go on a low iodine diet before the treatment to increase the effectiveness of the radioactive iodine. Once the TSH level is high enough, a whole body iodine scan is done by administering a small dose of radioactive iodine to determine if there are remaining thyroid cells that need to be destroyed. If enough cells show up on the whole-body iodine scan, a large dose of radioactive iodine (I131) is given, and then the thyroid pills are re-started. Radioactive iodine therapy has proved to be safe and well-tolerated, and it has even been able to cure cases of thyroid cancer that had already spread to the lungs. What is the follow-up for patients
with thyroid cancer? In addition to routine blood tests, your doctor may want to repeat periodically a whole-body iodine scan to determine if any thyroid cells remain. This can be done after your TSH level is raised, either by stopping your thyroid hormone and your becoming hypothyroid (see above) or by administering Thyrogen™ (synthetic human TSH) injections. What is the prognosis of thyroid
cancer? |
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Cancer of the Thyroid Brochure for Saving and Printing (PDF File, 328KB) |
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© 2008 American Thyroid Association. All rights reserved.
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