What are the current national averages for Lung-RADS (Lung Computed Tomography Screening Reporting and Data System) distribution of findings on an annual basis for individuals being screened in lung cancer screening programs?

National Lung-RADS Distribution in Lung Cancer Screening Programs

Current Distribution Data

Based on the most recent real-world screening data, approximately 24% of baseline screening examinations are classified as Lung-RADS 1 (negative), 60% as Lung-RADS 2 (benign), 10% as Lung-RADS 3 (probably benign), and 5% as Lung-RADS 4 (suspicious). 1

Baseline (First) Screening Round

• Lung-RADS 1 (Negative): 24% of examinations 1
• Lung-RADS 2 (Benign): 60% of examinations 1
• Lung-RADS 3 (Probably benign): 10% of examinations 1
• Lung-RADS 4 (Suspicious): 5% of examinations 1

These findings from the PROSPR Consortium represent contemporary community-based screening across five healthcare systems from 2014-2017, involving 8,556 patients at their first screening examination. 1

Positive Screen Rates Across Studies

The overall positive screen rate (Lung-RADS 3 or 4 combined) ranges from 9.4% to 27% depending on the screening round and population characteristics. 2, 1

• In the NLST, 27% of individuals had an abnormal screen on their first screening CT examination 2
• In other screening trials, up to 50% of subjects had an abnormal first screening CT examination 2
• A more recent clinical practice study found 9.4% were assigned Lung-RADS 3 and 7.9% were assigned Lung-RADS 4 3

Annual (Incidence) Screening Rounds

For subsequent annual screening rounds after the baseline:

• Lung-RADS 1: Approximately 76-77% 2
• Lung-RADS 2: Approximately 13-17% 2
• Lung-RADS 3: Approximately 6-7% 2
• Lung-RADS 4: Approximately 6% 2

The positive screen rate decreases substantially after the baseline screening, with 6-7% positive screens at year 1 and 5-6% at year 2 and beyond. 2

Cancer Detection Rates

Malignancy Frequency by Lung-RADS Category

The actual cancer frequency within each Lung-RADS category from real-world clinical practice is:

• Lung-RADS 3: 3.9% malignancy rate 3
• Lung-RADS 4A: 15.5% malignancy rate 3
• Lung-RADS 4B: 36.3% malignancy rate 3
• Lung-RADS 4X: 76.8% malignancy rate 3

These rates are notably higher than originally estimated in the Lung-RADS recommendations, particularly for category 3 and 4A nodules. 3

Overall Cancer Detection

• Only 4% of patients with a positive screen (Lung-RADS 3 or 4) had lung cancer in the NLST, meaning 96% of abnormal findings were false-positives 2
• The false-positive rate was 96.4% for the CT screening group in the NLST 2
• The cumulative risk of a false-positive result was 33% for a person undergoing two sequential annual examinations 2

Factors Affecting Lung-RADS Distribution

Patient Characteristics

Several patient factors significantly influence the likelihood of higher Lung-RADS categories:

• Age: Each additional year increases odds of Lung-RADS 3 (OR 1.02) and Lung-RADS 4 (OR 1.03) 1
• COPD: Strongly associated with Lung-RADS 4 (OR 1.78,95% CI 1.45-2.20) 1
• Obesity: Inversely associated with Lung-RADS 3 (OR 0.70) and Lung-RADS 4 (OR 0.58) 1
• Sex, race, ethnicity, education, and smoking status: No significant association with Lung-RADS assignment 1

Radiologist Factors

Notably, radiologist characteristics do not significantly affect Lung-RADS distribution, including:

• Volume of screening LDCT interpretations 1
• Years in practice 1
• Thoracic subspecialty training 1

Clinical Implications

Resource Planning

Healthcare systems with older patient populations or higher COPD prevalence will have a greater proportion of Lung-RADS 3 or 4 findings and should plan for additional resources to support appropriate and timely management. 1

Surgical Resection Rates

Among patients undergoing surgical resection in screening programs:

• 85% have confirmed lung cancer 4
• 15% have benign lesions despite Lung-RADS classification and risk stratification 4
• Of benign resections, 68% were solid nodules, 26% part-solid, and 5% ground-glass 4

Adherence to Follow-up

A critical gap exists in adherence to recommended screening intervals:

• For negative screens (Lung-RADS 1-2): only 23.7% return for annual screening at 1 year and 2.8% at 2 years 5
• For positive screens without cancer: 100% adhered to follow-up at 1 year but only 35.4% at 2 years 5

This poor adherence to annual screening represents a significant challenge to the effectiveness of screening programs and requires systematic interventions to improve. 5