askthedoctor Thyroid Cancer T Identify Thyroid
Cancer Early Ask your health care provider to screen you for thyroid cancer by palpating (feeling) for an enlarged thyroid.
48 MILITARY OFFICER JULY 2012
Though radiation exposure can increase the risk of thyroid cancer, routine diagnostic X-rays play an important role in preventive medicine. By Rear Adm. Joyce Johnson, D.O.
The thyroid is a small gland in the front of the neck. It is susceptible to abnor- mal growth, or nodules. Most nodules are benign and cause relatively few problems. However, about 5 to 10 percent of thy- roid nodules are malignant. A half million people in the U.S. have, or have had, thyroid cancer. Each year, about 60,000 new cases are diagnosed. If found early, the prognosis for thyroid cancer is excellent. The fi ve- year survival rate of patients with localized disease is greater than 99 percent. Risk factors for thyroid cancer include gender and age; about three times more women than men have thyroid cancer, and people over 45 are at greater risk as well, with most cases occurring between ages 35 and 65. A history of goiter or thy- roid nodule or a family history of thyroid cancer, goiters, or familial polyposis of the colorectal area also are risk factors. Radiation exposure is another known risk factor for some types of thyroid can- cer. People exposed to fallout from atomic weapons testing in the U.S. during the 1950s and ’60s are at increased risk. Radiation from nuclear power plant accidents, such as at Chernobyl in 1986 or in Japan after the March 2011 earthquake and tsunami, also increases the risk of thyroid cancer. Some medical treatments increase the
risk of thyroid cancer. For example, dur- ing the 1950s and ’60s, high-dose X-rays were used to treat acne, enlarged tonsils, and some skin disorders, often in chil- dren and adolescents. Children and ado-
lescents are more sensitive than adults to the eff ects of thyroid radiation. Though most people exposed to exces-
sive doses of radiation never develop thy- roid cancer, for those who do, the latency period (time from exposure to cancer di- agnosis) can be 10, 20, or more years. More recently, concern has risen about
the radiation exposure from routine diag- nostic X-rays. Though the doses are very low and modern equipment focuses the X-ray beam on the target areas, for some procedures — including dental X-rays — many people advocate the use of shields (sometimes attached to lead aprons) to protect the thyroid. Recently some have suggested thyroid shields should be used during mammo- grams. The American College of Radiology and the Society for Breast Imaging recom- mend against the use of a thyroid shield during mammography. The shield inter- feres with the picture and can result in ad- ditional fi lms being needed. Also, modern mammogram equipment focuses the beam on breast tissue, so the thyroid receives only minimal scatter radiation (equivalent to about 30 minutes of natural background radiation). Mammograms are an impor- tant part of preventive medicine.
MO
— Rear Adm. Joyce Johnson, USPHS-Ret., D.O., M.A., is vice president, Health Sciences, Battelle Memorial Institute, Arlington, Va. Find more health and wellness resources at www
.moaa.org/wellness. For submission information, see page 6.
PHOTO: STEVE BARRETT
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