Simple blood test spots early stage lung cancer

[Christine]

18 September 2007

NewScientist.com news service

Roxanne Khamsi

A simple blood test that identifies early lung cancer before it has had a chance to spread could save lives by alerting doctors to the need for treatment, researchers say.

The blood test looks for a telltale protein that is linked to tumour growth. In preliminary tests the process correctly identified 99% of patients with lung cancer at various stages of development.

Lung cancer claims the lives of 150,000 people each year in the US alone, making it the leading cause of cancer deaths. But doctors have lacked a means of accurately detecting lung tumours in the earliest stages.

Over the past decade, medical experts have explored the use of computed tomography (CT) body scans as a way to screen for lung cancer. But while patient advocacy groups say CT scans serve as a useful early detection tool, many chest physicians argue that they too often misidentify harmless scar tissue as cancer.

Mark Semenuk, a researcher at Panacea Pharmaceuticals in Gaithersburg, Maryland, US, says a simple blood test could provide a much simpler and more effective way to screen people at high risk of developing lung cancer, such as smokers.

Antibody Test

Semenuk and colleagues developed the test, which measures levels of a protein called human aspartyl beta-hydroxylase (HAAH) in the blood.

Scientists believe HAAH migrates to the surface of a cell to help make it receptive to chemical cues that promote growth. Laboratory findings also suggest that if the protein stays too long at the cell's surface, it may fail to mature properly, and can become cancerous.

The Panacea team suspected that too much HAAH may also get carried in the blood. So they measured HAAH levels in blood samples using antibodies that change colour when they bind to the protein.

In one experiment, they used this test to screen blood serum taken from 303 people, 160 of whom were known to have lung cancer at various stages of development. Their test accurately identified the presence of cancer in all but one of the patients with the disease.

Previous laboratory tests have suggested that more than 3 nanograms of HAAH per millilitre of blood to be abnormal. These people with lung cancer had an average HAAH count of 34 ng/ml of blood. Much lower levels of HAAH were found in the rest of the group, which included 93 non-smokers and 50 smokers. However, about 8% of those without the cancer had more than 3 ng/ml, triggering a handful of false positive results.

In a second experiment, the team screened blood from a further 60 patients with lung cancer at several known stages of development. This included 15 people with stage 1 lung cancer – the earliest stage of this illness and at which point the cancer has not yet spread. All 60 samples tested positive for cancer, indicating that the test can reliably detect the illness early on.

Improved Survival Rates

"We desperately need new methods for detecting lung cancer at the earliest stage possible," adds Regina Vidaver, executive director of the National Lung Cancer Partnership in Madison, Wisconsin, US. "Having a blood test that has high specificity with high sensitivity would greatly improve our abilities to diagnose lung cancer at earlier, potentially curable stages."

"Most people agree that you improve survival rates in cancer if you pick it up early," says Norman Edelman, chief medical officer for the American Lung Association in New York, US. But Edelman adds that further testing is necessary: "If this is really as good as they say, the next step is to look at a large population of smokers."

The test received approval for limited laboratory testing in July 2007, but the FDA has yet to approve a commercial version of the test.

Laurie Fenton, president of Lung Cancer Alliance in Washington, DC, US, says it will be a while before the true usefulness of the screening test becomes apparent. In the meantime, she says patients should consult their doctors about whether it makes sense for them.

Semenuk presented the lung cancer test at a meeting in Atlanta, Georgia, US, on molecular diagnostics in cancer therapeutic development run by the American Association for Cancer Research.