The Occupational Dimension of Lung Cancer Screening

Lung cancer continues to be a significant public health problem in the United States and worldwide. Ever since the increased use of cigarettes decades ago led to an epidemic of this disease, little has been available to alter the abysmal mortality rate, with fewer than one in five individuals surviving five years or more. The study by Markowitz et al. in this issue (p. 1296), which looks at low-dose computerized tomography (CT) screening for lung cancer, highlights this relatively new available technology and gives hope that improved outcomes may result.

DIMENSION OF OCCUPATIONAL EXPOSURE

This carefully done and thoughtfully reported study adds to earlier encouraging results from the expensive but successful National Lung Screening Trial (NLST) and extends the usefulness of this modality.¹ Whereas the NLST considered as a suitable population for testing only those exposed to cigarette smoke with certain criteria, this study, looking at more than 7000 nuclear weapons workers, considers occupational exposures and adds these considerations to the previous unidimensional aspect of smoking. Occupational physicians have known for some time that there are numerous types of exposures beyond cigarette smoking that lead to an excessive risk of lung cancer, ranging from arsenic and asbestos to radiation and silica. This study highlights that adding data on occupational exposure to asbestos and clinical nonmalignant manifestations of such exposure to a cigarette smoking history can be valuable. An added interesting aspect of this study is that it took place in predominantly nonmetropolitan areas where technology, which did not exist locally, was brought to the worker; by contrast, the NLST was almost exclusively done in urban centers. Locale should not be considered a barrier to an increased use of low-dose CT scanning.

The NLST showed that screening based on age and smoking history alone could lower lung cancer mortality by finding lesions at an earlier clinical stage that were much more likely to be cured.¹ In an appropriate set of individuals, some 1% were found to have previously undiagnosed lung cancers, many at stages I or II. This study adds the dimension of occupational exposure using lower smoking levels, but it added the issue of asbestos exposure. The thoughtfulness of the researchers can be found in many ways. All smokers were counseled regarding smoking cessation, something that every physician dealing with a smoking patient should do. Most CT scans were read by the same individual, giving great consistency to the readings. They also considered clinical pulmonary function status, and did not screen individuals whose altered lung function would not allow them to be considered for surgery, even if a lesion was found. On the basis of the NLST study, the US Preventive Services Task Force and insurance companies have recommended testing for appropriate individuals, but to date this testing is based only on cigarette smoking histories.²

This study highlights that there is great value in considering occupational exposures as well, and the finding in this study of roughly the same significant percentage of screened individuals with lung cancer, running about 1% of all comers, points to the legitimacy of their approach.

EXPAND THE USE OF LOW-DOSE CT SCANNING?

Given this expanded positive approach to screening for lung cancer and the reduced mortality that it engenders, it might be tempting to greatly expand the use of low-dose CT scanning for almost anyone with a smoking history or occupational exposures to carcinogens. However, this is not something to be recommended; rather, there is a need to determine the optimal point at which testing should be undertaken to maximize the usefulness of testing and the saving of lives. False positives can occur, which might lead some individuals to decide in hindsight that they have undergone significant but unnecessary surgical procedures. There are also the issues of cost, radiation exposure, and anxiety that might be engendered by unclear results. Another issue deserving of further study and refinement is the maximum age for testing. Current guidelines do not call for such testing among those aged 80 years or older, but this study found a significant number of lung cancers in this age group: individuals who still have, actuarially, nine or more years of expected life. Asbestos-related cancers turn up even in nonagenarians.

NUCLEAR WORKERS

It should also be noted that the funding source for this investigation was relatively nontraditional: the Department of Energy, which has a legal and moral requirement to look after the nuclear workers at many sites around the country. Occupational considerations are grossly underevaluated and underappreciated by the medical community at large. There are some 140 million working Americans, however, and the medical community needs to be better educated about exposures at work and in the environment more generally. Excellent studies such as this one highlight the importance of workplace exposure considerations.