Simple Saliva Test Could Improve Lung Cancer Detection
April 9, 2001 -- The elusive goal of developing a diagnostic tool to detect lung cancer in its very early stages -- when it's curable -- may be one step closer to reality. Japanese researchers have identified a specific protein that appears to be overproduced in lung cancer tissue and in precancerous lesions. If further research confirms this finding, a simple saliva test may one day be all that is needed to detect early-stage lung cancer, one of the researchers tells WebMD.
"Our findings strongly suggest that ... overexpression [of the protein] occurs very early in lung cancer and may be an early marker for detecting premalignant lesions of the lungs," says Hirota Fujiki, MD, of the Saga Medical School in Japan.
More Americans die of lung cancer each year than of colon, breast, and prostate cancers combined -- in part because the disease is rarely diagnosed at a time when it can be treated successfully. The American Cancer Society estimates that just under 170,000 new cases will be diagnosed this year, with almost 90% identified after the disease has spread beyond the lungs.
Earlier detection could save thousands of lives each year. The survival rate for all stages of lung cancer combined is around 15%, but it jumps to 42% for patients with early-stage disease who are treated with surgery.
But simply finding a way to detect lung cancer cells early would not necessarily have a dramatic impact on survival rates, Norman H. Edelman, MD, tells WebMD. Standard treatment for early lung cancer -- that has not spread outside the lung -- is surgery to remove the tumor, but if there is no observable tumor, there is nothing to cut out, he says. Edelman is dean of the school of medicine at State University of New York at Stony Brook and a consultant for the American Lung Association.
"There is some evidence that looking for cancer cells in [saliva] might work for early detection, but if there is nothing apparent on an X-ray, there is no clear way to treat lung cancer at this stage," Edelman says. "Knowing that these cells are present may help clinicians locate a tumor by X-ray or CT scan, but that is conjecture at this point."
New and improved scanning devices may help detect lung cancers while they are curable, he says. Studies now under way are evaluating the usefulness of two of these devices -- spiral CT and PET scans. These screening methods have been shown to be more sensitive than X-ray in detecting suspicious lesions in the lungs.
Fujiki and colleagues' findings may also aid lung cancer prevention trials. The Japanese researchers have studied the cancer prevention properties of green tea for several years, and in this study they found that green tea extract prevented overproduction of the protein in lung cancer cells.