A spiral CT scan provides a better quality image and is four to ten times more accurate than a conventional chest x-ray in diagnosing lung cancer. With a chest x-ray, lesions as small as a few millimetres may go unnoticed because the rib cage or spine may hide them.
Lesions can also be difficult to differentiate from blood vessels on a x-ray.
Scientists are optimistic that the three-pronged approach will help identify precancerous and cancerous lesions when they're small enough to be treated successfully. Because early lung cancer shows no symptoms, the disease often goes undiagnosed until a late stage when the five-year survival rate is less than 15 per cent. If physicians can locate the disease earlier, however, the odds for survival could jump from 15 per cent to more than 80 per cent. The three tests being used by researchers are complementary, according to Dr. Stephen Lam, the principal investigator of the study. The sputum test provides an indication of any cancerous or precancerous changes.