Computed tomography screening for lung carcinoma in Japan

In Japan, lung carcinoma is the leading cause of cancer-related deaths. Adenocarcinoma accounts for roughly half of all lung carcinomas. Earlier detection of lung carcinoma is expected to reduce mortality rates. Computed tomography (CT) provides higher contrast resolution and greater visualization of chest compartments that are difficult to view with chest radiography, such as the mediastinum. CT further permits the detection of minute peripheral nodules. At present, several institutions and research groups are evaluating the utility of low dose spiral CT for lung carcinoma screening.

From September 1993 to December 1998, 1669 individuals underwent a biannual screening program for lung carcinoma. The program included posteroanterior radiograph, sputum cytology, and low dose spiral CT at a for-profit organization: The Anti-Lung Cancer Association (ALCA). A total of 9993 examinations were carried out. The low dose spiral CT parameters used were 120 kvP, 50 mA, 10-mm collimation, and 2:1 pitch.

Peripheral lung carcinoma was detected in 31 of 9993 examinations (0.3%). Of the 31 cases, 24 tumors (77%) were detected by low dose spiral CT but were not visible on standard chest radiography. Twenty-two of the 24 tumors were Stage IA (T1N0M0, according to staging system revised in 1997).

Low dose spiral CT shows promise for lung carcinoma screening. The effectiveness of the technique for the detection of minute lung lesions remains to be established. Routine use of the technique will require resolution of several issues. These issues include the establishment of CT diagnostic criteria, the development of a diagnostic support system, the establishment of methods for definite diagnosis, and assessments of efficacy.