The implementation of population-based lung cancer screening (LCS) in the United States has been delayed for more than four decades, even though radiographic studies in the 1970s and 1980s had already demonstrated improvements in survival. Several factors have contributed to this prolonged lag, including apprehensions about overdiagnosis and false positives, ongoing debates about the necessity of multiple randomized controlled trials (RCTs), initial restrictions limiting screening to only high-risk individuals, and widespread concerns regarding radiation exposure.
Despite substantial evidence by 2024 affirming that computerized tomographic (CT) screening can prevent lung cancer (LC) deaths by detecting tumors at an earlier, more treatable stage, a remarkably low percentage of eligible individuals partake in screening.
Early Observations and Smoking-Related Epidemic
By the 1960s, lung cancer had become a leading cause of cancer mortality, fueled by high rates of cigarette smoking. The government began warning the public about the harmful link between smoking and lung cancer in 1964, but therapeutic options for late-stage disease were extremely limited. During the 1970s, roentgenographic (chest radiograph) screening studies suggested that early detection could extend survival. Yet, it was not until 2015 that the Centers for Medicare and Medicaid Services (CMS) started offering coverage for CT lung cancer screening, which had already shown success in multiple trials.
Landmark Trials and Evolving Technology
After World War II, large-scale tuberculosis screening led to the incidental detection of early lung tumors, suggesting potential benefits for population-wide programs. However, major U.S. trials funded by the National Cancer Institute in the 1970s indicated that screening with chest X-rays did not significantly reduce lung cancer mortality.
By the early 1990s, rapidly advancing CT technology had enabled precise imaging of lung nodules and potential lung cancers under two centimeters and as small as 6 mm in diameter. The 1991 Early Lung Cancer Action Program (ELCAP) demonstrated that CT could identify up to 80% of cases at Stage 1, substantially boosting survival probabilities. Japan had also adopted this technology for broader screening, documenting high five-year survival rates among these screen-detected patients.
The International Early Lung Cancer Action Program (IELCAP) and the National Lung Screening Trial (NLST) launched around the same time confirmed meaningful reductions in both lung cancer mortality by 21% and overall mortality by 7%. IELCAP demonstrated markedly improved survival after screen detection of LC, but because it did not have a control group, it could not assess mortality reduction. Subsequent European trials echoed and amplified these findings, reporting even greater mortality reductions. In 2015, CMS approved coverage for high-risk individuals, albeit requiring “shared decision making” using official decision aids.
Some of the early decision aids were misleading because they relied on old data, leading to lots of false alarms and unnecessary invasive procedures for people who didn’t have cancer. Critics jumped on this, claiming most people flagged by screening would still die of lung cancer anyway. However, newer studies with longer follow-up have shown that survival rates are much better when stage I cancers are found through regular CT scans. Large-scale European trials employing stringent diagnostic algorithms also demonstrated much lower false-positive rates.
Radiation Fears, Eligibility Constraints, COVID-19, And The Allure of Biomarkers
Despite the growing body of evidence, only about 5% of eligible Americans undergo CT lung cancer screening. Uptake is substantially higher in some states. Critics have cited overdiagnosis bias, radiation risks, and complications from false positives in questioning the value of screening programs. Published guidelines and opinion pieces further entrench these views. Faced with conflicting viewpoints, primary care providers often hesitate to recommend screening, unsure about benefit-risk ratios.
Misinformation about radiation hazards has also stifled broader acceptance. Advocacy of the linear non-threshold (LNT) model led some experts to attribute an increased malignancy risk to even minimal CT doses. Further complicating matters, earlier guidelines restricted eligibility, excluding many at-risk individuals. Recent changes have widened the eligible population, but broad acceptance remains elusive. As with other cancer screening, the COVID-19 pandemic exacerbated these obstacles by delaying screening appointments and dissuading people from seeking preventive care.
A growing interest in blood-based diagnostics competes for attention, though many current assays lack the sensitivity or practicality to replace CT imaging, especially at scale. Critics also dispute the cost-effectiveness of widespread CT LCS. Consistent findings from multiple RCTs and real-world programs reveal that CT LCS can substantially reduce mortality, making it a cost-effective strategy for high-risk individuals.
Nonsmokers and Overdiagnosis Controversies
The prevalence of LC in never-smokers—particularly among women—has been rising. While certain researchers remain skeptical about extending screening to lower-risk groups, emerging evidence suggests early detection benefits these individuals. Ironically, those who once warned of overdiagnosis in heavy smokers now cite it for nonsmokers, despite data indicating that many screen-detected cancers are indeed life-threatening if left untreated.
Population-level CT LCS has been needlessly postponed for over 40 years, largely due to entrenched misconceptions: a belief in a substantial reservoir of harmless lung tumors and an overestimation of screening risks. Early research provided compelling data by the 1990s and was reinforced by subsequent work. Nevertheless, fear of overdiagnosis, excessive concern about radiation, and misapplied cost-effectiveness models continue to influence practice. Yet the facts remain clear: detecting lung cancer early through low-dose CT prevents a significant number of deaths, far exceeding any associated harms. If the medical community and policymakers can overcome the longstanding misinformation, many more lives may be saved, mitigating a grim legacy of avoidable mortality.
Sources: Why has there been such a long delay in the implementation of population lung cancer screening in the USA? Academia Medicine DOI: 10.20935/AcadMed7560
