By Amanda Gardner
MONDAY, May 19 (HealthDay News) -- Lung cancer patients may be one step closer to the day when the disease can be detected early with a simple blood test.
Scientists slated to report their findings Tuesday at the American Thoracic Society's conference in Toronto say the test -- which tracks gene activity in immune-system cells -- was very good at distinguishing patients with lung cancer from those without the disease.
"The findings are important and represent progress," said Dr. Norman Edelman, chief medical officer of the American Lung Association. "They may not be good enough [yet] to change practice. I'm sure, as the researchers refine it, it'll get better and better."
Lung cancer remains the number one cancer killer of men and women. According to the National Cancer Institute, 215,020 new cases of the disease will be diagnosed in 2008, and 161,840 Americans will die of lung cancer.
Lung tumors are notoriously difficult to spot when they are still small enough to be treated effectively, leading to an astronomically high death rate from the disease.
A technology known as CT screening can detect lung cancer in 20 percent to 60 percent of people tested, but it also has a high false-positive rate, meaning that patients often have to endure repeat or follow-up testing.
"If you do a CT scan on a general population, you are going to find lots of little nodules, and the critical issue is, what's cancer and what's not," Edelman said. The CT scan method is also controversial, with one study finding that higher detection rates did not translate into lower death rates.
"If they had a minimally invasive blood test that doesn't involve a biopsy that would tell whether or not something is cancer, that would be a huge advantage," Edelman said.
Researchers have long been looking for a simple blood test to detect lung cancer, many of them trying to find proteins released into the bloodstream by the tumor. But lung cancer is so heterogeneous, involving many different cell types, that this goal has so far proved illusive.
The authors of this study followed a different strategy, measuring gene expression profiles in lymphocytes (immune system cells) to see if they correlated with the presence or absence of lung cancer. "The hypothesis is the immune system has some sort of interplay with the cancer and, from that interplay, you get changes in the genes that are expressed," said Dr. Anil Vachani, lead author of the study and assistant professor of medicine at the University of Pennsylvania School of Medicine in Philadelphia.
A 24-gene signature tested in 137 patients with early-stage lung cancer and 91 healthy controls had overall 87 percent accuracy in identifying who had cancer and who did not.
"I would say that 87 percent is very good, but it's not excellent," Vachani said. "For a test to be really useful clinically, it has to do a little bit better."
A second study, also involving genetics and also being presented at the American Thoracic Society meeting, assessed how well five different high-risk genetic signatures predicted the likelihood of a recurrence in patients who had been diagnosed early with non-small cell lung cancer and then undergone surgery.
According to a team from Columbia University, New York City, the gene signature profiles were 40 percent to 100 percent accurate in predicting a recurrence of the disease, depending on the type of tumor. This could help physicians determine who should get more aggressive therapy, the authors stated.
For more on lung cancer, visit the National Cancer Institute.