Screening of Eligible Former Workers for Early Lung Cancer with Low-Dose Helical Computed Tomographic (CT) Scans
The Department of Energy (DOE) CT Scan Pilot Program
Lung cancer results in approximately 160,000 deaths in the U.S. every year. The most common causes of lung cancer are long-term exposures to tobacco smoke and residential radon emissions, but occupational hazards such as asbestos and ionizing radiation also cause or contribute to the burden of disease.
Credit: Teresa Winslow(artist), for NCI
Nevertheless, the evidence according to the National Institutes of Health (NIH) Trial has been inadequate to determine whether screening by low-dose helical computed tomography (LDCT) reduces mortality from lung cancer sufficiently to outweigh the solid evidence that harms result from false-positive test results and unnecessary invasive diagnostic procedures and treatments. As a result, DOE and others have examined the potential for early detection of lung cancer with LDCT scans over the past 10 years.
Since 2000, DOE has made screening for occupational lung cancer with LDCT scans available to workers at high-risk for lung cancer through the Former Worker Medical Screening Program (FWP). This LDCT pilot program initially consisted of at-risk current and former workers associated with the three gaseous diffusion plants (Oak Ridge K-25, Paducah, and Portsmouth), but was subsequently expanded to include former workers associated with the Y-12, Oak Ridge National Laboratory, Mound, and Fernald sites.
Figure 1 depicts DOE sites where LDCT is being provided by DOE's pilot program. Over 10,000 former workers have participated, a number of cases of lung cancer have been identified in the earliest stages with potential for cure or increased survival, and a small body of scientific literature has been generated. However, the conduct of a randomized, large-scale trial assessing the impact of LDCT upon mortality and providing a comprehensive analysis of benefits and harms was never possible without the leadership and resources of an agency such as the NIH.
The National Institutes of Health (NIH) Trial
In August 2002, the NIH National Lung Screening Trial (NLST) began a landmark randomized, national trial involving more than 53,000 current and former heavy smokers at risk of lung cancer. The NLST compared the effects of two screening procedures for lung cancer - LDCT and chest X-rays. The participants were randomly assigned to one of two groups: a study group who received annual LDCT for 3 years and a control group who received annual chest x-ray for 3 years.
By October 2010, a total of 354 deaths from lung cancer had occurred among participants in the LDCT arm of the study, as compared with 442 lung cancer deaths among those in the chest X-ray group. The NLST Data and Safety Monitoring Board (DSMB) recommended that NIH end the study, because the accumulated data which demonstrated a 20.3 percent reduction in lung cancer mortality had met the standard for statistical significance. These initial findings were released by NIH in November 2010, and the publication of the complete NLST study and its peer review (i.e., the open exchange of supporting and opposing views in a journal) are eagerly anticipated in the Spring of 2011. According to NIH:
"The possible disadvantages of screening for lung cancer with CT scans include the cumulative effects of radiation from multiple scans; surgical and medical complications in patients who prove not to have lung cancer but who need additional testing to make that determination; and risks from additional diagnostic work-up for findings unrelated to potential lung cancer, such as liver or kidney disease. In addition, the screening process itself can generate suspicious findings that turn out not to be cancer in the vast majority of cases, producing significant anxiety and expense. These problems must, of course, be weighed against the advantage of a significant reduction in lung cancer mortality."
The National Institute for Occupational Safety and Health (NIOSH) Investigation
In January 2011, NIOSH posted on the NIOSH Science Blog an article entitled "Helical CT Scans and Lung Cancer Screening" which communicated the high level of interest of NIOSH in reviewing the data generated by the NLST with the objective of determining its applicability to screening individuals at risk of lung cancer due to occupational exposures. NIOSH has begun working with the NIH investigators who conducted the NLST and will consider carefully the complete, published NLST findings which are anticipated in the Spring of 2011. According to the Blog:
"The NLST investigators are conducting more comprehensive analyses to assess adverse events related to the screening, as well as healthcare utilization for all reasons related to the acquisition of the images, and quality-of-life and cost-effectiveness endpoints. They will be publishing their peer-reviewed findings in the early spring of 2011. NIOSH will consider these findings carefully, consult further with the NIH investigators, and work with stakeholders in labor, industry, and the occupational medicine clinical community to consider the meaning of these findings for workers potentially at risk for lung cancer because of occupational exposures."
Taken together, the knowledge and data generated by DOE, NIH, and others relating to screening for lung cancer with LDCT strongly suggests that the early detection of lung cancer will at long last become a key component of both public and occupational health programs where the risk of lung cancer is significantly increased as a result of risk factors such as tobacco smoke or occupational exposures.
The DOE FWP's strengths center on the use of the best available, evidence-based approaches to determine possible causality of disease, and screening for lung cancer is an area that could potentially make a huge difference. While national medical authorities begin their discussions on how to apply these findings throughout the country, DOE FWP will continue to provide this type of screening at selected DOE sites for participants who meet eligibility requirements, including a history of at-risk occupational exposures.