Which population should be screened with Low-Dose Computed Tomography (LDCT) scan?

Lung Cancer Screening with LDCT: Target Population

Screen adults aged 50-80 years with ≥20 pack-year smoking history who currently smoke or quit within the past 15 years, as this represents the most current evidence-based recommendation that maximizes mortality reduction. 1, 2

Primary Screening Criteria (USPSTF 2021 - Current Standard)

The 2021 USPSTF guidelines expanded eligibility compared to older recommendations, and this is now the standard of care:

• Age: 50-80 years (expanded from the previous 55-80 threshold) 1, 2
• Smoking history: ≥20 pack-years (reduced from the previous 30 pack-year requirement) 1, 2
• Current smoker OR quit within past 15 years 1, 2
• Asymptomatic individuals only - symptomatic patients need diagnostic workup, not screening 3

Pack-Year Calculation

• 1 pack per day × 30 years = 30 pack-years 1
• 1.5 packs per day × 20 years = 30 pack-years 1

Alternative Criteria from Other Organizations

While USPSTF provides the most current recommendation, other major organizations maintain slightly different thresholds:

• NCCN, ACS, IASLC: Age 55-74 years with ≥30 pack-years (Category 1 recommendation) 4, 1
• ACCP: Age 55-80 years with ≥30 pack-years 4, 3

The USPSTF 2021 criteria should be prioritized as they are most recent and capture more at-risk individuals who benefit from screening. 2

Absolute Contraindications to Screening

Do not screen individuals with:

• Health problems that substantially limit life expectancy or ability to undergo curative lung surgery 1, 3
• Requirement for home oxygen supplementation 1
• Chest CT performed within past 18 months 1
• Active symptoms suggestive of lung cancer - these patients need diagnostic evaluation, not screening 3

When to Stop Screening

Discontinue screening when:

• Patient has not smoked for 15 years 3, 2
• Development of health problems limiting life expectancy or surgical candidacy 3, 2
• Patient reaches age 80 years 1, 2

Critical Implementation Requirements

Screening must only be performed in high-quality centers with specific capabilities - this is not optional:

• Multidisciplinary teams including thoracic surgeons, radiologists, pulmonologists, and oncologists 4, 1
• Expertise in LDCT interpretation and lung nodule management 1, 3
• Access to comprehensive diagnostic and treatment services 1, 5
• Smoking cessation counseling programs 1, 3

Mandatory Patient Counseling

Before screening, patients must receive shared decision-making discussion about:

• Benefits: 20% relative reduction in lung cancer mortality 2
• Harms: High false-positive rates, potential for invasive procedures, radiation exposure, overdiagnosis 4, 3
• Smoking cessation: Screening is NOT a substitute for quitting 1, 3

Common Pitfalls to Avoid

• Do not screen patients under age 50, even with strong family history or other risk factors - there is insufficient evidence and this violates all established guidelines 1
• Do not use chest radiography for screening - it does not reduce mortality and should never be used 1
• Do not screen without access to multidisciplinary follow-up - this increases harms without maximizing benefits 4, 1
• Do not forget smoking cessation counseling - this remains the single most effective intervention to reduce lung cancer risk 1, 3

Technical Screening Parameters

When performing LDCT:

• 120-140 kVp, 20-60 mAs 3, 5
• Average effective dose ≤1.5 mSv 3, 5
• Collimation ≤2.5 mm 3
• Annual screening interval 3, 5