Utility of low-dose helical CT as a second step after plain chest radiography for mass screening for lung cancer.

We evaluated the usefulness of low-dose helical computed tomography (CT) as a routine second step in patients screened for lung cancer with plain chest radiography (PCR). Of 5,437 people who underwent mass screening for lung cancer by PCR, further work-up was required for 230 because of abnormal findings. Of 221 subjects who had CT as a second step, abnormal shadows were detected in 110 and no abnormal shadows were seen in 111. Screening CT (helical scan; beam collination, 10 mm; pitch of 2:20 mm/s; and tube current, 50 mA) detected 17 lung cancers, 87 benign lesions, and 6 extrapulmonary lesions, with an average diameter of 10 mm (range, 2-35 mm). All lung cancers were peripheral (12 stage I, 4 stage IIIA, and 1 stage IV). In 40% of screened subjects, 37 with benign lesions and 7 with lung cancer (6 stage I), lesions were delineated only by screening CT. In conclusion, low-dose helical CT was found to be useful as a second step in patients who have been screened for lung cancer by PCR and can delineate the early stage of lung cancer.