How can we detect curable early lung cancer?
Lung cancer is the leading cause of cancer mortality worldwide. In 2006, 45941 men and 17314 women died from lung cancer in Japan. Despite modest improvements in the treatments for lung cancer during the last few decades, the over-all 5-year survival rate still remains approximately 15%. Therefore, to reduce the number of deaths from this lethal disease, the early detection followed by definitive treatment is essential. Annual chest X-ray has been the usual screening procedure for the early detection for lung cancer. However, several randomized controlled trials (RCTs) during the 1970s failed to demonstrate a reduction in lung cancer mortality by means of screening with chest radiography1). The Mayo Lung Project2) was the largest RCT among them. In this study, 9212 participants were randomized to a screening group, which underwent annual chest X-ray and sputum cytology every 4 months, and to a non-screening control group. After 9 years, the number of detected lung cancer was significantly higher in the screening group than that in a control group (p=0.013), whereas there were no significant differences in lung cancer mortality between the 2 groups (p=0.62). On the basis of these results, screening for lung cancer has been considered to have no effect on the reduction of cancer mortality in the United States. However, with the recent advances in radiology, the efficacy of lung cancer screening is still under intense investigation. In this article, I review some recent trials for the early detection of lung cancer and discuss the interpretation of the results.