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CA: A Cancer Journal for Clinicians, Vol 30, 199-207, Copyright © 1980 by American Cancer Society

Cancer of the Lung

It is important to review the evidence and rationale used by the Society in reaching its conclusion not to recommend the use of annual chest x-rays to screen asymptomatic people for lung cancer. Several studies, conducted mostly in the 1960s, have failed to demonstrate a benefit from screening for lung cancer with chest x-rays and/or sputum cytology, used in various combinations as frequently as every six months. The only randomized, controlled trial that evaluated the effectiveness of an annual chest x-ray was conducted by the Kaiser Permanente Health Plan, and in this study there was virtually no difference in overall mortality in the study and control groups.

Three more intensive studies are currently in progress. Two, being conducted at Memorial Sloan-Kettering Cancer Center and Johns Hopkins University, are not designed to evaluate the annual chest x-ray. If any difference in mortality in the study and control groups is found in these trials, it will be due to the sputum cytology offered every four months to the study group. At the Mayo Clinic the study group is offered an intensive screening program with both sputum cytology and chest x-rays offered every four months. The study group was advised to have yearly chest x-rays and sputum tests, but no reminders were sent. At present, none of the studies show a statistically significant improvement in overall mortality due to screening. Even with intensive screening—the use of two tests delivered three times a year—there is no statistically significant improvement in mortality after five years of evaluation.

Despite this, all three programs, as well as the programs conducted in the l960s, demonstrate that both tests can detect cancers in asymptomatic people, that they appear to result in a higher proportion of people having cancer detected in earlier stages, and that case-survival rates of those detected in earlier stages are good. These results suggest that someday it may be possible to demonstrate that screening for lung cancer is beneficial. However, the meaning of the stage of a cancer at the time of detection, and of case-survival rates, is extremely difficult to interpret because of the existence of lead time biases, length biases, patient selection biases, and the possibility of overdiagnosis. It is precisely to avoid these biases that randomized, controlled trials are designed and that overall mortality is used as the ultimate outcome in determining the value of screening.

Based on this information, on the possibility of some risks associated with the workup of patients with false-positive test results, and on the high cost of screening, the Society did not feel it would be responsible to advocate screening for a large group of people (e.g., approximately 20 million smokers over 40) without better evidence that they would derive some benefit. The Society recognizes, however, that every case is different, and that individual physicians and patients may decide that the evidence of benefit is sufficient to warrant the use of these screening tests on an individual basis. This is entirely appropriate provided the evidence of benefits and the costs and risks are clearly understood. Thus, the Society's recommendation is intended only as a guideline for asymptomatic people, and as with all the other recommendations, should be tailored to fit the needs of individual cases.

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