Last year we posted two blogs on the use of computerized tomography (CT) scans of the chest for lung cancer screening — Helical CT Scans and Lung Cancer Screening¹  and Low-dose CT Scans and Lung Cancer Screening in the Occupational Setting.²   Since the postings, various organizations have provided guidance with differing implications for early detection of lung cancer in workers who have been exposed to lung carcinogens in the occupational setting. This blog provides an update on scientific investigation and the various recommendations that have been made in this area.

Background

The National Cancer Institute (NCI) – sponsored National Lung Screening Trial (NLST) was the first randomized controlled trial to demonstrate a mortality benefit from CT screening for lung cancer. It studied a population at very high risk for lung cancer. Participants had to be current or former heavy smokers (30 pack-year or greater) who were 55 to 74 years old. They were screened with low dose CT (LDCT) once a year for 3 years³. The findings from the NLST were an exciting milestone in the effort to detect lung cancer at an early stage, when it can still be treated effectively. Some information from the NLST, such as cost-effectiveness of LDCT screening and its impact on quality of life, will be reported in the future.

Efforts are underway to determine how NLST’s findings should be applied to public health practice. Public health recommendations will need to balance the benefits of screening vs. harms such as diagnostic evaluations of false positive results or cancer from radiation. This balance might be different for groups different from those studied in NLST. Even in the high risk group studied in NLST, “false positive” non-malignant lung nodules were far more frequently detected than malignant lung nodules. NLST researchers are working with the Cancer Intervention and Surveillance Modeling Network, a branch of NCI, to use modeling techniques to estimate the potential benefits and harms of LDCT screening in other groups of smokers and other age groups. Modeling the balance between benefit and harm might be influenced by important aspects of public health recommendations such as the optimal frequency of screening, how long screening should be continued, and how indeterminate nodules should be followed up after identification. NLST investigators have advised policy makers to wait for more information before endorsing LDCT lung-cancer screening programs.

Guidelines Recommended by Professional Societies

In the wake of NLST, several professional societies have released guidelines for LDCT lung-cancer screening. The National Comprehensive Cancer Network (NCCN), a consortium of 21 U.S. cancer treatment centers, released their lung cancer screening guidelines in October 2011⁴. The NCCN recommended screening with LDCT for people aged 55 and greater with smoking histories of 30 or greater pack-years who still smoked, or quit smoking less than 15 years ago (NLST criteria). In addition to those who would have met NLST inclusion criteria, NCCN also recommended LDCT screening for people aged 50 and greater with smoking histories of 20 or greater pack-years and one additional risk factor other than second-hand smoke.  A variety of additional risk factors are described, including COPD,  pulmonary fibrosis, and various occupational exposures (asbestos, arsenic, chromium, silica, nickel, cadmium, beryllium and diesel fumes). Although the NCCN recommendation includes occupational exposure to lung carcinogens, it provides no guidance as to how much exposure is needed before LDCT screening for lung cancer should be considered.

In April 2012, the American Lung Association released a guidance statement⁵ to patients and physicians indicating that LDCT screening should be recommended only for people who meet NLST criteria because of the questions that remain about optimal methods and effectiveness in other populations. Soon after, in May 2012, the American College of Chest Physicians  and the American Society of Clinical Oncology , with collaboration from the American Cancer Society , released their clinical practice guidelines⁶, based on a systematic review of the evidence regarding the benefits and harms of lung cancer screening with LDCT. They recommend that only people who specifically meet NLST criteria should undergo LDCT screening, and not to screen individuals who have accumulated fewer than 30 pack-years of smoking; are either younger than 55 years or older than 74 years; individuals who quit smoking more than 15 years ago; or individuals with severe comorbidities that would preclude potentially curative treatment, limit life expectancy, or both.

Finally, in July 2012, screening guidelines were issued by the American Association for Thoracic Surgery. These recommended annual lung cancer screening with LDCT for smokers and former smokers with a 30 pack-year history of smoking; those with a 20 pack-year history of smoking and additional comorbidity that produces a cumulative risk of developing lung cancer of 5% or greater over the following 5 years; and long-term lung cancer survivors, aged 55 to 79 years. The  American Association for Thoracic Surgery guidelines differ from the others since they recommend that screening begin at age 50 years and end at age 79, instead of 74, arguing that there is little evidence to show that lung cancer risk drops after that age. They also differ in recommending the screening to patients who have survived lung cancer⁷.

The U.S. Preventive Services Task Force, a government-appointed panel that issues guidelines for clinical prevention, is at the first stage of research plan development to issue new recommendations on this topic. Their last recommendation for lung cancer screening was made in 2004. At the time, they concluded that there was insufficient evidence to recommend for or against screening asymptomatic persons for lung cancer with LDCT, chest x ray (CXR), sputum cytology, or a combination of these tests⁸. However, it is likely that the task force will reconsider its recommendation in light of NLST.

Screening in the Occupational Setting – The Department of Energy Experience

There has been no randomized controlled trial of LDCT for lung cancer screening of working populations exposed to lung carcinogens. An example of LDCT screening of an occupational group that was not done as part of a randomized controlled trial is the voluntary Early Lung Cancer Detection Program offered to former and current Department of Energy workers. Former and current nuclear weapons workers aged 45 years or older, including smokers and never-smokers with variable exposure to occupational lung carcinogens, are offered annual LDCT screening if they meet determined risk criteria. The follow-up of indeterminate nodules is part of the screening program and based on the I-ELCAP protocol⁹. This is aimed at keeping invasive procedures and radiation exposure to a minimum. Since the program started in 2000, over 10,500 Department of Energy workers have received LDCT scans through the program and 71 lung cancers have been detected. The majority (72%) were found in early stages¹⁰. Participants also benefited from the screening by early detection of diseases in other organs (e.g., cancer of the kidney, cancer of the thyroid, and aortic aneurysm) and lung diseases other than cancer (e.g., emphysema, asbestosis, pulmonary fibrosis) that were unknown to the subject at the time of screening.

Anticipated Future Developments

We anticipate that this area will continue to evolve rapidly as new data from NLST is published and the findings are translated into public health recommendations from groups such as the U.S. Preventative Services Task Force. NIOSH will continue to monitor these developments and work to assure that recommendations address the needs of those at risk for lung cancer from occupationally-related exposures.

Simone Tramma, MD, MS; Eileen Storey, MD, MPH; David Weissman, MD

Dr. Tramma is a Medical Officer in the Surveillance Branch of the NIOSH Division of Respiratory Disease Studies.

Dr. Storey is Chief of the Surveillance Branch in the NIOSH Division of Respiratory Disease Studies.

Dr. Weissman is Director of the NIOSH Division of Respiratory Disease Studies.

References

1. Tramma S, Storey E, Trout D, Sweeney M. Helical CT Scans and Lung Cancer Screening. NIOSH Science Blog. Available at https://blogs.cdc.gov/niosh-science-blog/2011/01/helical/
2. Tramma S, Storey E, Trout D, Sweeney M. Low-dose CT Scans and Lung Cancer Screening in the Occupational Setting. NIOSH Science Blog. Available at https://blogs.cdc.gov/niosh-science-blog/2011/08/ct-scan/
3. National Lung Screening Trial Research Team. Reduced Lung-Cancer Mortality with Low-Dose Computed Tomographic Screening. N Engl J Med 2011; 365:395-409.
4. Wood DE, Eapen GA, Ettinger DS, et al. Lung Cancer Screening. J Natl Compr Canc Netw 2012; 10:240-265.
5. American Lung Association. Providing Guidance on Lung Cancer Screening To Patients and Physicians, April 2012. Available at http://www.lung.org/finding-cures/research-news/new-screening-guidelines/lung-cancer-screening.pdf
6. Bach PB, Mirkin JN, Oliver TK, et al. Benefits and harms of CT screening for lung cancer: a systematic review. JAMA; published online May 20, 2012. Available at http://jama.jamanetwork.com/article.aspx?articleID=1163892
7. Jacobson FL, Austin JH, Field JK, et al. Development of The American Association for Thoracic Surgery guidelines for low-dose computed tomography scans to screen for lung cancer in North America: Recommendations of The American Association for Thoracic Surgery Task Force for Lung Cancer Screening and Surveillance. J Thorac Cardiovasc Surg 2012; 144(1):25-32.
8. U.S. Preventive Services Task Force (USPSTF). Lung Cancer Screening Recommendation Statement 2004. Available at http://www.uspreventiveservicestaskforce.org/3rduspstf/lungcancer/lungcanrs.htm
9. Henschke PI. International Early Lung Cancer Action Program: Enrollment and Screening Protocol. Available at www.ielcap.org/professionals/docs/ielcap.pdf
10. Worker Health Protection Program (WHPP) Early Lung Cancer Detection (ELCD) Program. Available at http://www.cbns-environmentalhealth.org/WHPP-ELCD.html