The Mayo Lung Project followed over 9000 male smokers over 45 years of age who smoked one or more packs a day from 1971 to 1986 and compared intensive CXR and sputum screening every three times per year compared to less frequent annual screening. The results showed that more frequent screening resulted in higher resectability rate (more early-stage detection), but made no difference in mortality from lung cancer. CXR screening were found to detect 6 times as many new cancers as sputum tests.