medwireNews: The US Preventive Services Task Force (USPSTF) has updated its recommendations for lung cancer screening with low-dose computed tomography (LDCT) among current and former smokers.
Writing in an editorial accompanying the recommendation statement in JAMA, Ethan Basch (University of North Carolina at Chapel Hill, USA) and co-authors note that the update has two “significant changes” compared with the 2013 version.
“The first change reduces the age at which to initiate annual screening from 55 to 50 years. The second change reduces the smoking intensity from 30 to 20 pack-year history,” they write.
The editorialists say that “[t]he 2021 USPSTF recommendation statement represents a leap forward in evidence and offers promise to prevent more cancer deaths and address screening disparities,” but they believe “the greatest work lies ahead to ensure this promise is actualized.”
Basch and colleagues continue: “While expanded eligibility criteria are an important step toward equity, barriers to screening, including lack of insurance coverage and physical access to high-quality screening programs, highlight the complex implementation issues to be addressed.”
To inform the recommendation, the USPSTF commissioned a systematic review and a modeling study, both of which are also published in JAMA and were conducted, respectively, by Daniel Jonas (The Ohio State University, Columbus, USA) and colleagues and Rafael Meza (University of Michigan, Ann Arbor, USA) and co-workers.
Screening reduces mortality but also causes harms
The systematic review drew on 223 publications, including 26 articles reporting on seven randomized controlled trials, and addressed key questions regarding the benefits, accuracy, and harms of LDCT screening.
Jonas et al note that the National Lung Screening Trial (NLST) and Nederlands-Leuvens Longkanker Screenings Onderzoek (NELSON) study – comprising 53,454 and 15,792 participants, respectively – were the only trials adequately powered to assess the effect of screening on mortality.
Screening involved three rounds of annual LDCT in NLST and four rounds at increasing intervals in NELSON and both led to a reduction in lung cancer mortality. NLST also demonstrated a decrease in all-cause mortality with LDCT screening versus chest radiography.
Other studies also pointed to the benefits of screening, with, for instance, increases in the detection of early-stage cancers and corresponding decreases in late-stage disease in the five trials that reported on this outcome.
However, screening was also associated with harms. For instance, data from 12 studies showed that the rates of overdiagnosis ranged from 0.0% to 67.2%, while false-positive rates, which could be ascertained from 27 publications, were in the range of 7.9–49.3% for the baseline screen and 0.6–28.6% for subsequent screening rounds.
Jonas and co-workers also highlight “short-term increases in distress because of indeterminate results,” but note that radiation-induced cancers were rare.
Modeling data identify optimal parameters for screening
The modeling study used four Cancer Intervention and Surveillance Modeling Network (CISNET) simulation models to assess 1092 LDCT screening strategies that estimated the lung cancer risk either based on risk factors (age, cumulative pack–years, and years since quitting) or using simplified versions of risk prediction models.
Meza and colleagues report that “[c]ompared with no screening, risk factor–based screening strategies were estimated to result in lung cancer deaths averted and life-years gained, with variations according to the level of screening (number of LDCT screenings) and specific eligibility criteria for each scenario.”
They also identified 57 “consensus-efficient scenarios,” which were estimated to provide the greatest benefit for a given level of screening. Of these, 25 were associated with a 9% or greater reduction in lung cancer mortality, with estimated numbers of deaths averted ranging from 348 to 578 per 100,000 people and life–years gained ranging from 4490 to 8186 per 100,000 people. The number of patients needed to screen to avert one lung cancer death ranged from 34 to 63.
The estimates for the six strategies that used 20 pack–years as a risk factor and involved annual screening were 469–558 per 100,000 people for deaths averted, 6018–7596 per 100,000 people for life–years gained, and 42–45 for number needed to screen. By contrast, the 2013 USPSTF criteria were estimated to lead to 381 deaths averted per 100,000 people, 4882 life–years gained, and a number needed to screen of 37.
The selected 20 pack–year scenarios were also calculated to increase the proportion of the population ever eligible for screening to 20.6–23.6% from 14.1% with the 2013 USPSTF criteria.
But compared with the 2013 criteria, these strategies were also estimated to lead to more false-positive results (1.9–2.5 vs 1.9 per screened individual), biopsies (526–849 vs 518 per 100,000 people), overdiagnosed cases (83–94 vs 69 per 100,000 people), and radiation-related lung cancer deaths (29.0–42.5 vs 20.6 per 100,000 people).
The study authors additionally report that “[r]isk model–based strategies were estimated to result in considerably more lung cancer deaths averted for a given number of LDCT screenings than risk factor–based strategies,” but “the differences in life-years gained were less pronounced.”
USPSTF recommendation statement
On the basis of these data, “[t]he USPSTF concludes with moderate certainty that annual screening for lung cancer with LDCT has a moderate net benefit in persons at high risk of lung cancer based on age, total cumulative exposure to tobacco smoke, and years since quitting smoking,” say Alex Krist (Virginia Commonwealth University, Richmond, USA) and fellow authors of the recommendation statement.
They therefore write: “The USPSTF recommends annual screening for lung cancer with LDCT in adults aged 50 to 80 years who have a 20 pack-year smoking history and currently smoke or have quit within the past 15 years.
“Screening should be discontinued once a person has not smoked for 15 years or develops a health problem that substantially limits life expectancy or the ability or willingness to have curative lung surgery.”
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