Office of Cancer Communications Building 31,Room 10A24 Bethesda, MD 20892 |
National Cancer Institute August 1, 1997 FOR RESPONSE TO INQURIES |
Backgrounder |
Background Information on Thyroid Cancer and Radiation Risk Scientists do not know what causes most cases of thyroid cancer. One known risk factor is exposure to radiation during childhood. Children who received x-ray treatments for noncancerous conditions such as enlarged tonsils, enlarged thymus gland, and possibly acne and ringworm of the scalp have a higher-than-average risk of developing thyroid cancer many years later. Children exposed to radioactive fallout from nuclear explosions in the 1950s may also be at risk; however, scientists do not yet have a reliable way to estimate the risk of thyroid cancer from radioactive fallout. Thus far, studies of exposure to radioactive iodine (I-131) for medical purposes or from fallout in areas close to the site of atomic bomb tests during the 1950s have produced no conclusive evidence that such exposure to I-131 is linked to cancer . However, the possibility that I-131 may be related to thyroid cancer continues to be studied. Of particular importance will be information obtained from studies of children and adults exposed to varying levels of fallout from the Chernobyl accident, where an increase in thyroid cancer is apparently related to exposure to high doses of I-131. How common is thyroid cancer? Thyroid cancer is uncommon, accounting for just one percent of all cancers in this country. Each year about 16,000 cases of thyroid cancer are diagnosed in the United States, with an estimated 1,230 deaths (about two tenths of one percent) from this disease. This type of cancer occurs more often in women than in men and is most often found in young adults and teenagers. What is the thyroid? The thyroid is a gland located in the neck, below the Adam's apple. It makes and stores hormones that help regulate heart rate, blood pressure, body temperature, and the rate at which food is converted into energy. Thyroid hormones also help children grow and develop. The thyroid uses iodine, a mineral found in some foods and iodized salt, to make its hormones. What are the symptoms of thyroid cancer? The most common symptom of thyroid cancer is a lump, or nodule, that can be felt in the neck. Other symptoms are rare. Pain is seldom an early warning sign of thyroid cancer. However, a few patients have a tight or full feeling in the neck, difficulty breathing or swallowing, hoarseness, or swollen lymph nodes. These symptoms can be caused by thyroid cancer or by other, less serious problems. How is thyroid cancer detected? During a physical checkup, the doctor examines the neck, feeling for lumps in the thyroid and enlargement of nearby lymph nodes. How is thyroid cancer treated? Surgery is the major form of treatment, usually followed by treatment doses of I-131. For further information, call the Cancer Information Service at 1-800-4-CANCER.
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