Lung Cancer Blood Test in the Works
Test Looks for Clues From Immune System in People With Lung Cancer
May 19, 2008 -- A new blood test for lung cancer is 87% accurate in early studies.
Unlike most other cancer blood tests, the new lung cancer test doesn't look for particles thrown off by cancer cells as they grow wildly. Instead, it looks for the genetic signature of immune-system cells activated by encounters with tiny lung tumors.
In a way, the test doesn't find lung cancer. It just tells your doctor what your body already knows -- in time to do something about it. Anil Vachani, MD, and colleagues are developing the test at the University of Pennsylvania.
"We have been able to show, in a preliminary fashion, that there are real differences in gene expression in people with lung cancer," Vachani tells WebMD. "Using some of those differences, you can predict which people had cancer and which did not, with about 87% accuracy."
None of these genetic differences appears before a person has lung cancer. What happens, Vachani explains, is that white blood cells patrol the body. When they encounter lung cancer cells, a specific set of genes becomes active.
"We believe white blood cells interact with the lung tumor and are changed due to the interaction," Vachani says. "And we can detect these changes by looking at gene expression in the blood cells."
In its most recent version, the blood test looks for 24 different genes. Vachani says that when the technique is optimized, the number of genes in the analysis will range from the teens up to 100.
"Once we feel we have optimized as well as we can, by testing lung cancer patients and noncancer patients and comparing the results, we have to do a prospective study and see if it works in a true clinical fashion," Vachani says. "That is something we hope to do in the next few years."
Vachani says the early tests now involve 130 lung cancer patients and 90 control patients. He presented his findings at the International Conference of the American Thoracic Society.
New Lung Cancer Tests Needed
Why a blood test for lung cancer? Current screening involves CT scans, which are not only expensive but highly inaccurate. This results in a lot of false-positive lung biopsies and even surgeries, says lung disease specialist Edward Hirschowitz, MD, assistant professor of medicine at the University of Kentucky.
"We want ultimately to have a test that tells us who is most likely to get lung cancer, and in which patients CT scans are most warranted," Hirschowitz tells WebMD.
Hirschowitz praises the Vachani team's work. He says that their genetic screen for white blood cells is unlikely to miss cases of cancer, but he worries that the test will not be able to tell true cancer patients from those with other conditions.
"My concern is that if somebody has pneumonia or black lung, they will have a similar profile to cancer patients," he says.
Hirschowitz and colleagues are also working on a lung cancer blood test that looks at the immune system. Their test, however, focuses on another arm of the immune system -- antibodies; it looks for antibodies that recognize lung cancer cells.
Using blood samples drawn from patients who underwent CT scans, Hirschowitz and colleagues were able to predict -- with about 80% accuracy -- which patients would develop lung cancer in one to five years.