Mass screening for lung cancer with mobile spiral computed tomography scanner

Summary

Background

The incidence of and mortality from lung cancer have increased steadily. Most lung cancers are not localised when first detected, but early detection is mandatory to improve prognosis. Since curable early cases are hard to visualise with conventional chest radiography, a new diagnostic means must be found. We assessed whether population-based mass screening with a spiral computed tomography scanner could contribute substantially to detection of smaller cancers, and decrease mortality.

Methods

In 1996, we screened in a mobile unit 5483 individuals from the general population of Matsumoto, Japan, aged between 40 years and 74 years who had undergone annual chest radiography (miniature fluorophotography) and cytological assessment of sputum. All participants had a low-dose X-ray spiral computed tomography (CT) scan of the thorax; 3967 also underwent miniature fluorophotography. We compared smokers and non-smokers. Further assessments were done for probably benign but suspicious lesions; suspicion of cancer; and indeterminate small nodules by chest radiography and conventional CT, with additional transbronchial biopsy when possible. Thoracotomy was recommended when it was strongly suspected that the patients had lung cancer.

Findings

19 patients were diagnosed as having lung cancer-14 with suspicion of lung cancer, three with benign but suspicious lesions, and two with indeterminate small nodules. 18 cases were surgically confirmed, and one was clinically diagnosed. The mean size of lesions was 17 mm (range 6–47). In four of 19 patients, lung abnormality was seen on CT and miniature fluorophotography. The lung-cancer detection rate with CT was 0·48%, significantly higher than the 0·03–0·05% for standard mass assessments done previously in the same area. CT missed one case that was found solely on a sputum cytology examination.

Interpretation

Our results show that miniature fluorophotography or conventional chest radiography, which have been the main diagnostic techniques for lung cancer, showed few small cancers. CT was more accurate in mass screening for lung cancer and led to early detection and an accurate diagnosis of lung cancer, and should be considered in future health plans.

Introduction

Lung cancer has the highest mortality rate of cancers in Japan. Early detection is necessary to improve its prognosis. Although chest radiography has been widely used for screening, small peripheral lung cancers are not seen clearly.1, 2, 3, 4, 5, 6, 7, 8, 9, 10 Therefore, a diagnostic technique that detects cancers in an early stage is needed to decrease the mortality of lung cancer.9, 10, 11 A low-dose X-ray spiral computed-tomography (CT) scanner has been used to screen for lung cancer.¹² We did a population-based study that involved mass screening for lung cancer with such a spiral CT system to assess how this method contributes to the detection of smaller cancers and to find out whether spiral CT and conventional chest radiography differ in detection of lung cancer.

This trial is expected to continue for 2 more years at the Matsumoto Research Center (an agency established in 1995 to investigate the application of advanced digital network systems in telemedicine). We report mortality from lung cancer with a 1-year follow-up after the first 3 years of CT screening.