Complete implementation of the CT screening protocol used in the National Lung Screening Trial (NLST) could avert 12,250 deaths annually in the U.S., according to a study published online Feb. 25 in CANCER. An accompanying editorial questioneed some implications of nationwide screening in the U.S.

Although the NLST demonstrated a 20 percent mortality reduction with annual CT screening among high-risk adults, the impact of a national screening implementation is unknown. Jiemin Ma, PhD, MHS, from the surveillance research program at the American Cancer Society, and colleagues estimated the number of deaths avertable by screening.

The researchers used 2010 U.S. Census data, the prevalence of screening eligibility and lung cancer mortality rates to derive their estimates.

In 2010, a total of 8.6 million U.S. adults, 5.2 million men and 3.4 million women, met NLST screening criteria (ages 55 to 74 years with a 30 pack-year history). If all eligible adults participated in screening, 12,250 deaths could be delayed or prevented annually according to Ma et al.

However, the estimate is subject to variables. The NLST report acknowledged the 20 percent mortality reduction may be an underestimate, while universal screening compliance may be overly optimistic.

The researchers modeled various simulations which estimated avoidance of 18,375 deaths at a 100 percent screening uptake rate and 30 percent mortality reduction, and 6,125 deaths averted at a 50 percent uptake rate and 20 percent mortality reduction.

In an accompanying editorial, Larry Kessler, ScD, chair of the department of health services at the University of Washington, Seattle, explored the balancing act of screening and other ongoing prevention efforts, specifically smoking cessation. “In many ways, these efforts must go hand-in-hand because the population who has accumulated many pack-years of smoking will indeed benefit from a well-implemented program of secondary prevention.”

Kessler posed the question: Does the 20 percent mortality reduction and 12,000 lives saved justify a national screening policy?

He referred to the high rate of false-positive findings  and the unknown risk-benefit balance of CT screening. Kessler also cautioned against screening outside of organized screening programs, which may be prone to additional potential harms, and reiterated the International Association for the Study of Lung Cancer’s call for CT screening demonstration projects, quality metrics and task forces to address areas of uncertainty.

Despite the unknowns, Kessler affirmed the value of screening.

“The message of the estimates given in the study by Ma et al, as well as the overall context of smoking and lung cancer (and other smoking-related diseases and deaths), compels us to use all of our technologies, primary prevention methods, screening methods and treatment to the best of our ability as a nation,” he concluded.