The National Lung Screening Trial (NLST) is a randomized multicenter study comparing low-dose helical computed tomography (CT) with chest radiography in the screening of older current and former heavy smokers for early detection of lung cancer, which is the leading cause of cancer-related death in the United States. Five-year survival rates approach 70% with surgical resection of stage IA disease; however, more than 75% of individuals have incurable locally advanced or metastatic disease, the latter having a 5-year survival of less than 5%. It is plausible that treatment should be more effective and the likelihood of death decreased if asymptomatic lung cancer is detected through screening early enough in its preclinical phase. For these reasons, there is intense interest and intuitive appeal in lung cancer screening with low-dose CT. The use of survival as the determinant of screening effectiveness is, however, confounded by the well-described biases of lead time, length, and overdiagnosis. Despite previous attempts, no test has been shown to reduce lung cancer mortality, an endpoint that circumvents screening biases and provides a definitive measure of benefit when assessed in a randomized controlled trial that enables comparison of mortality rates between screened individuals and a control group that does not undergo the screening intervention of interest. The NLST is such a trial. The rationale for and design of the NLST are presented.
The editorial cited by Dr Eddy was provoked by the February 1980 ACS report on "The Cancer-Related Health Checkup."1That report, prepared for the ACS by Dr Eddy, emphasized that its recommendations pertained only to early detection of cancer on an individual basis and not to "mass screening programs at public expense."1 Our editorial comment was likewise confined to individual case-finding initiated by patients.2We are on record as being opposed to noncontrolled large-scale screening programs initiated by any organization. Our concern is that Dr Eddy seems to use "screening" and "early detection" interchangeably. In his letter he writes: the ACS is aware that x-ray films can detect cancers in asymptomatic persons and that the cancers often appear to be detected in early stages. The Society is also aware, however, of the many biases that can cause an interpretation of staging information and case-survival rates
RESULTS of treatment of lung cancer today leave much to be desired. A recent study indicated that the five-year survival rate in all patients with bronchogenic carcinoma was still less than 15%.1There is evidence, however, that this gloomy prognosis can be improved, provided that the tumor can be discovered while it is still resectable.2 At present, cytologic examination of sputum (or bronchial secretion) constitutes the most accurate diagnostic test for lung cancer of any procedure short of thoracotomy with lung biopsy. Roentgenographic procedures may be more sensitive, but they are primarily screening devices and cannot confirm the diagnosis of malignancy as cytology studies can. Published reports3indicate that cancer cells can be detected in sputum or bronchial secretions of about two thirds of patients with primary bronchogenic carcinoma and one third of those with metastatic cancer to the lung. As might be expected, figures in different
In a necropsy study of 50 cases of ventricular septal defects, the anatomic position and relations of ventricular septal defects, the causes of and ages at death, and association of ventricular septal defects with other cardiovascular malformations were determined. The present availability of surgical closure of ventricular septal defects makes this information of practical significance.
Several important aspects of the Mayo Lung Project demand evaluation. These are: 1. Acceptance. Will people accept such a screening program? 2. Case finding. Does the screen pick out the people most likely to have or develop bronchogenic carcinoma? 3. Effectiveness. If an early case of bronchogenic carcinoma is found, will prompt treatment extend life beyond the time at which death from this disease would have occurred if treatment had been delayed? Direct measurement of effectiveness is not possible, and indirect methods must be used. A group of patients, all of whom are considered suitable for the screening program, are being divided randomly into two subgroups, one to be screened and the other to be kept as an unscreened control. Mortality in the two groups is to be compared for 5 years, and hopefully for 10 years. We also consider here sample size requirements and reports on some of the characteristics of the first 500 patients.
