In August 2011, results of the National Lung Screening Trial (NLST) were published in the New England Journal of Medicine. The study found that low-dose CT (LDCT) screening correlated with a reduction in lung cancer-specific mortality of 20% when compared with radiography. In September 2011, the American Association of Thoracic Surgeons (AATS) launched a task force to interpret NLST and several similar European trials in order to establish guidelines on lung cancer screening. The resulting recommendations were recently published in the Journal of Thoracic and Cardiovascular Surgery.
The AATS recommendations for use of LDCT in lung cancer screening were most heavily influenced by NLST. The study was specifically designed to answer whether LDCT could positively affect mortality risk for 30 pack-year smokers aged 55 to 74 with a baseline 10-year risk of 2% for developing lung cancer. The NLST also heavily influenced guidelines from other professional societies on LDCT screening.
A Tiered Approach for Lung Screening
The AATS guidelines use a three-tiered approach. In tier one, it recommends annual LDCT screening from age 55 to 79 for those with a 30 pack-year smoking history. The AATS recommends continuing screening to age 79 because:
• The peak incidence of lung cancer in the
United States is age 70.
• The average life expectancy in the U.S. is
78.6 years.
• Age alone is a risk factor for lung cancer.
The AATS recommends that screening cease at age 79 because the advantages of early detection are unclear among those aged 80 or older.
Tier two includes yearly LDCT screening for patients as young as 50 with a 20 pack-year history of smoking and an additional risk factor that raises their 5-year risk of developing lung cancer to 5%. These risk factors include COPD with forced expiratory volume in 1 second of 70% or less than predicted, environmental and occupational exposures to radon and other carcinogens, and a genetic or family history.
“The 2012 AATS recommendations for use of LDCT in lung cancer screening were most heavily influenced by NLST.”
The third tier involves screening of patients who’ve had a previous lung tumor removed. These individuals are at the highest risk of developing lung cancer. Although these patients have been cured of the disease, the carcinogens that were inhaled that created the lung cancer were also absorbed throughout all of their lung tissue, allowing for other areas of the lung to also become cancerous. For this tier, the AATS guidelines recommend yearly high-resolution CT scans for 4 years following surgical resection of stages 1A to IIIA, followed by LDCT screening beginning in the fifth year. LDCT screening should be repeated every year indefinitely until patients no longer have functional status and the pulmonary reserve needed for treatment of a new lung cancer.
The Future of Lung Cancer Screening
Research in lung cancer screening is progressing rapidly, and breath or blood tests are under development. These advances may be achievable within 10 years. Either would be less expensive than CT screenings and could avoid false positive results.
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