Blood Test May Spot Asbestos-Linked Cancer

Test May Help Screen High-Risk People, Researchers Say

From the WebMD Archives

Oct. 12, 2005 -- A blood test could help screen for pleural mesothelioma, an asbestos-related cancer, a new study shows.

The test checks blood levels of a protein called osteopontin.

Blood osteopontin levels "rise dramatically" in the early stages of pleural mesothelioma, says researcher Harvey Pass, MD, in a news release.

"A rise in the level of this biomarker in workers with past asbestos exposure may indicate to physicians that these people need to be followed even more closely for the development of cancer," he says.

Pass is the chief of the division of thoracic surgery and thoracic oncology in the cardiothoracic surgery department at New York University's medical school. He is also a professor of surgery there.

About Asbestos

Asbestos is a naturally occurring mineral fiber. Its uses have included insulation, fire protection, and construction materials.

Asbestos is not always an immediate hazard, according to the Environmental Protection Agency.

"In fact, if asbestos can be maintained in good condition, it is recommended that it be left alone and periodic surveillance performed to monitor its condition," states the EPA's web site.

"It is only when asbestos-containing materials are disturbed or the materials become damaged that it becomes a hazard. When the materials become damaged, the fibers separate and then may become airborne," the web site states.

Rare Disease

Pleural mesothelioma is a rare disease of the lining of the lung and chest cavity that is usually cancerous. Its only known cause is asbestos exposure, says the EPA, noting that it can take 15-30 years for the disease to emerge.

Pleural mesothelioma has been hard to detect in its early, more treatable stages. As a result, many patients die within months of diagnosis, write Pass and colleagues.

There are 2,500 to 3,000 new mesothelioma cases in the U.S. per year. Over the years, millions of workers have been exposed to asbestos, mainly in industrial, construction, and maintenance jobs, note the researchers.

They cite estimates that as many as 7.5 million American construction workers have used construction materials containing asbestos. Asbestos is "still a hazard" for an estimated 1.3 million U.S. workers in construction and building/equipment maintenance, the researchers add.

Not all people with asbestos exposure get cancer; however, exposure to asbestos and other substances such as coal, fuels, and arsenic can increase your risk of lung cancer. Smoking further increases the risk for cancer in those with asbestos exposure.

"Researchers still have not determined a 'safe level' of exposure, but we know the greater and longer the exposure, the greater the risk of contracting an asbestos-related disease," says the EPA.


New Blood Test

Pass and colleagues did osteopontin blood tests on 190 people, 76 of whom had pleural mesothelioma. Sixty-nine patients had asbestos-linked lung disease that wasn't cancerous.

For comparison, the study also included 45 current or former smokers with no asbestos exposure.

Most participants who had been exposed to asbestos had worked in an asbestos-related trade for at least five years.

Study's Findings

Higher osteopontin blood levels were linked to pleural mesothelioma but not to noncancerous asbestos-related lung diseases, the study shows. There also was little difference in the osteopontin levels between the 69 noncancerous asbestos-related lung disease participants and the 45 people without asbestos exposure. Osteopontin levels were similar for men and women.

It's not yet clear if high blood osteopontin levels indicate other kinds of asbestos-related cancer.

Osteopontin and Cancer

Osteopontin has been studied as a possible marker for other cancers before. For instance, it's one of four proteins being tried as a potential blood test for ovarian cancer.

The researchers write that "asbestos workers with high osteopontin levels who do not appear to have mesothelioma should be evaluated to rule out the presence of other cancers."

Larger studies confirming the test's usefulness and evaluating its role for other cancers need to be done.

The new blood test isn't justified for the general public, write the researchers.

WebMD Health News Reviewed by Louise Chang, MD on October 12, 2005


SOURCES: Pass, H. The New England Journal of Medicine, Oct. 13, 2005; vol 353: pp 1564-1573. News release, New York University Medical Center and School of Medicine. U.S. Environmental Protection Agency: "Asbestos -- What Is It?" U.S. Environmental Protection Agency: "Asbestos -- What Are Its Uses?" WebMD Medical News: "Progress in Blood Test to Detect Ovarian Cancer."

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