WASHINGTON (Reuters) -- A blood test that looks for the body's own immune response to tumors may provide an easy way to find lung cancer in patients long before an X-ray or CT scan could, U.S. researchers have reported.
The test correctly predicted non-small-cell lung cancer in blood samples taken from patients years before their lung cancer was actually diagnosed, the researchers reported.
If the test's reliability can be confirmed, it might become the first new blood screen for any cancer since the prostate specific antigen or PSA test. The test is licensed to privately held Rockville, Maryland-based 20/20 GeneSystems Inc.
"These data suggest antibody profiling could be a powerful tool for early detection when incorporated into a comprehensive screening strategy," the researchers wrote in their report, published in the Journal of Thoracic Oncology.
Non-small-cell lung cancer is the most common type of lung cancer, and has an average five-year survival rate of only 40 percent.
Lung cancer is by far the biggest cancer killer globally. Each year 10 million people learn they have it, according to the Global Lung Cancer Coalition, and half of all patients die within a year of diagnosis. It kills more than 160,000 people annually in the United States alone.
Special X-rays known as computed tomography or CT scans can find lung cancer tumors, but they have a high rate of false positives -- meaning many people have to undergo a painful biopsy to get a piece of a suspicious lump out of the lung, only to find out it was not cancerous after all.
By the time people have symptoms of lung cancer, it is usually too late to save them.
Li Zhong and colleagues at the University of Kentucky developed a test that looks for certain proteins the body makes in response to very early lung tumors.
When they tested it in people who were being treated for lung cancer, it correctly identified 90 percent of cases, and with very few false positives in samples taken from people who did not have lung cancer.
They went back and tested blood samples taken from some of the lung cancer patients years before their cancer was diagnosed. The test found cancer in four out of seven samples taken a year before diagnoses, and in all 18 samples taken two, three and four years earlier.
"Based on doubling times, a lung cancer can be present three to five years before reaching the conventional size limits of radiographic detection," Zhong's team wrote.