There is a considerable literature on the use of chest radiography as a screening tool for early lung cancer. These trials have been of all varieties, including randomised controlled trials (RCTs). Some have been undertaken in conjunction with sputum cytology. Two early important trials were performed in Japan. Although designed differently and coming to slightly different conclusions in large numbers of patients, these mass screening programmes concluded there was a benefit associated with chest X-ray screening and sputum cytology compared to non-screening. These studies were both case-controlled studies.
The next landmark study was the Mayo Lung Project performed between 1971 and 1983, a randomised controlled trial on nearly 11,000 patients. Rather than a case-control study, this RCT also set out to determine whether chest X-ray and sputum cytology provided an effective means of screening for lung cancer. Perhaps unusually, patients were randomised into two different screening regimes, screened annually or every 4 months for 6 years, with further follow-up. This study demonstrated a clear stage shift in the more frequently screened patients, resulting in a better 5-year survival but at 20-year follow-up there was no overall survival benefit. Further large studies from the Memorial Sloane Kettering Hospital, the Johns Hopkins lung project and a Czechoslovakian study all had insufficient statistical power to demonstrate a reduction in mortality between screened and non-screened patients. Since the question remained open to doubt, the prostate, lung, colorectal and ovarian cancer screening trial, recruiting between 1993 and 2001 at screening centres across the United States, attempted to resolve whether chest X-ray could be used as an effective screening technique for lung cancer and result in subsequent reduction in mortality.
Unlike previous studies, many of the enrolees were never smokers (45%), or non-smokers (42%) and only about 10% were current smokers. Of the total 154,000 men and women enrolled, only 24,000 were considered to be of high risk for lung cancer. In this study, despite a slight stage shift in the screening group, there is no difference in lung cancer deaths between the screen group and the usual care group. From these various trials, providing some contradictory data, it can be reasonably concluded that chest X-ray alone has no useful role in lung cancer screening. Although lung cancers may be detected, often at a slightly earlier stage, the eventual outcome between screened and non-screened groups is almost identical.
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