Panel rejects screening for thyroid cancer

Wednesday, Sept. 2, 1998 | 10:55 a.m.

Although some 160 million Americans exposed to nuclear bomb fallout from the Nevada Test Site are at higher risk for developing thyroid cancer, a federal panel said Tuesday the government should not sponsor a screening program.

There is no evidence to suggest that early detection of thyroid cancer caused from radioactive iodine-131 through routine screening would lengthen lives or lead to other health benefits, the panel's report said.

Instead, the government should involve the public and medical experts in designing information programs about fallout exposure from 100 atom bomb experiments triggered above ground, risks of developing thyroid cancer and potential benefits and drawbacks of testing for the disease.

The iodine-131 report was released by committees of the Institute of Medicine (IOM) and National Research Council.

"A national or regional screening effort could result in needless worry and unnecessary surgeries because the tests used to detect the disease are so often inconclusive," IOM Committee Chair Robert Lawrence said.

"Fortunately, the kind of thyroid cancer linked to radiation exposure is rarely fatal," said Lawrence, associate dean for professional education and programs at the Johns Hopkins School of Public Health in Baltimore.

People across the country were exposed to iodine-131 for about two months following each test in the 1950s and 1960s. The U.S. banned nuclear weapons tests in the air in 1963. The radioactive iodine has a half-life of eight days, meaning half of its radioactivity remains after eight days.

While some people inhaled the radioactive iodine carried in fallout, many received doses in their milk, especially children living on family farms and drinking milk from cows or goats. Individual doses ranged widely, the report said.

Nine out of 10 people diagnosed with thyroid cancer linked to radiation live longer than 30 years after the cancer is found, the report said. All forms of thyroid cancer account for less than 1 percent of total cancer deaths each year.

The report estimates about 1.2 million thyroid cancers will develop in a 70-year span. The National Cancer Institute estimates 11,300 to 212,000 additional thyroid cancers could develop as a result of exposure to radioactive iodine.

But the panel found no data indicating a screening program would improve these survival rates.

To screen for thyroid cancer, doctors first search for lumps on the gland. If cancer is suspected, a tissue sample is necessary. About 25 percent of such samples are false-positive or cannot be determined. Even some malignant growths will not grow or cause health problems.

A national or regional screening program could result in physicians referring people to unnecessary surgery. Once the thyroid is removed, a lifetime of hormone replacement therapy is usually necessary.