- Lung cancer screening criteria based on the duration of smoking appeared to be a better option for determining individuals at highest risk for lung cancer in an observational study.
- Compared with USPSTF recommendations, criteria based on the minimum number of years smoked (20, 30, or 40 years) identified more individuals most expected to benefit from screening.
- A threshold of at least 40 years of smoking was also more effective than the USPSTF in excluding people least expected to benefit from screening.
Lung cancer screening criteria based on smoking duration appeared to be a better method of evaluating lung cancer risk than current guidelines that use pack-years and years since cessation, according to results from a nationally representative cohort study.
Researchers found that years-smoked thresholds ranging from 20 to 40 years captured a greater proportion of individuals likely to benefit most from low-dose CT screening compared with U.S. Preventive Services Task Force (USPSTF) eligibility criteria, reported Lauren Kearney, MD, of Boston University School of Medicine, and colleagues.
There was a trade-off with the less stringent thresholds, however. For example, a minimum of 20 years of smoking captured almost all of the individuals who had the highest chance of benefit, but it greatly expanded the screen-eligible population compared with USPSTF criteria and included many of the lowest-benefit individuals.
“Smoke duration thresholds are simple to apply and identify more people who may benefit from [lung cancer screening] than USPSTF criteria,” wrote Kearney and colleagues in JAMA Internal Medicine. “However, they entail trade-offs between effectiveness and efficiency and population size. Decision-makers must weigh these trade-offs according to priorities such as resource availability and the imperative to avoid missing those who may gain the most.”
Uptake of low-dose CT screening for lung cancer has been pretty abysmal, with fewer than 20% of eligible individuals undergoing screening, according to some estimates. One recent study found that increasing lung cancer screening uptake to 100% of eligible individuals could more than quadruple the number of lung cancer deaths prevented over a 5-year period, researchers found.
The USPSTF in 2021 expanded eligibility for screening by lowering the pack-year threshold to 20 years as well as the age at screening initiation to 50 years, with the objective of making more high-risk individuals eligible for screening.
“Emerging evidence suggests total years smoked may better capture risk than current guidelines,” observed Kearney and colleagues. However, they added, “the optimal years-smoked threshold for screening remains uncertain.”
In fact, a growing body of evidence suggests “no single simplified eligibility rule can fully capture the heterogeneity of lung cancer risk among individuals who ever smoked,” according to an accompanying editorial by Iakovos Toumazis, PhD, of the University of Texas MD Anderson Cancer Center in Houston, and colleagues. The best way forward could be combining simplified eligibility rules with individualized risk prediction, they wrote.
“As screening programs continue to evolve, policies that balance simplicity, efficiency, and precision will be essential to maximizing the benefits of [lung cancer screening] while minimizing potential harms,” the editorial said.
Kearney and colleagues used 2024 National Health Interview Survey (NHIS) data to categorize individuals into three groups based on the Life-Years from Screening–CT model, which estimates a person’s projected life expectancy increase with screening: those who gained the greatest benefit in life-years gained from screening, those who gained an intermediate benefit, and those who got the least benefit.
The authors then compared the screening population impacts of the USPSTF criteria versus those based on numbers of years smoked (≥20, ≥30, or ≥40 years).
The NHIS data included 57 million individuals ages 40 to 80 years (mean 59.1 years, 55% men) who had ever smoked. The mean years smoked was 26.
USPSTF guidelines captured 77% of the highest-benefit individuals; the most stringent smoking duration threshold of ≥40 years captured 85% of them. The 40-year smoking duration criterion also did better than the USPSTF in excluding those expected to benefit the least (100% versus 98%).
The 30- and 20-years smoked thresholds captured most of the highest-benefit individuals (97% and 99%, respectively) but excluded fewer of the lowest-benefit individuals than did the USPSTF criteria (69% vs 96%).
Among those selected by the criterion of at least 40 years smoking, 68.8% were highest-benefit and 0.1% were lowest-benefit. A threshold of at least 30 years smoking added mostly intermediate-benefit individuals, and lowering the threshold to 20 years smoked added many patients with the lowest screening benefit.
According to Kearney and colleagues, the smaller screening population identified by the most stringent threshold of at least 40 years smoked might align with health systems that have limited screening capacity. As for the 15% of the highest-benefit individuals missed with that threshold, the authors said this could be addressed using individual risk assessments.
An intermediate threshold of at least 30 years’ smoking duration provides a middle ground that captures most of the highest-benefit individuals and excludes most lower-benefit individuals, the researchers noted.
“Given the trade-offs identified in this study, the choice of years-smoked criterion should reflect priorities including efficiency vs maximal capture of high-benefit individuals,” they concluded. “Criteria should be implemented with individualized risk assessment, decision support, and capacity planning to balance benefits, harms, and feasibility.”
