Volume doubling time of lung cancers detected in a chest radiograph mass screening program: Comparison with CT screening.

The aim of this study was to evaluate the volume doubling time (VDT) of lung cancer detected in our annual chest radiograph screening program and to compare it with those previously reported for computed tomography (CT) screening. In total, 209 patients who had a measurable tumor shadow and a history of participating in our chest radiograph mass screening program between 2006 and 2009 were included in this study. Indirect roentgenograms for patients with lung cancer were converted into digital images, and the section showing the tumor was enlarged on the monitor to a size of 0.01 mm. The mean VDT for all the patients was 158 days. Only 3.8% of the patients had a VDT of more than 400 days. In 140 patients with adenocarcinoma, the mean VDT was 177 days, and 5.0% of these patients had a VDT of more than 400 days. In the 44 patients with squamous cell carcinoma, the mean VDT was 133 days, and only 2.3% of these patients had a VDT of more than 400 days. These results were different from those previously reported for CT screening. In several reports on CT screening, more than 20% of the lung cancers had VDTs of more than 400 days. Since it is common knowledge that there are 'indolent' lung cancers with a VDT of more than 400 days, screening by annual chest radiography with rare overdiagnosis may need to be reconsidered.