What are the guidelines for low dose lung computed tomography (low dose lung CT) screening for lung cancer?

Low-Dose CT Screening Guidelines for Lung Cancer

Annual low-dose CT screening for lung cancer should be offered to asymptomatic individuals aged 55-77 years with a 30+ pack-year smoking history who currently smoke or have quit within the past 15 years, and should also be considered for those aged 50-80 years with a 20+ pack-year smoking history. 1, 2

Primary Eligibility Criteria

• Strong recommendation for annual LDCT screening for individuals aged 55-77 years with ≥30 pack-years smoking history who currently smoke or have quit within past 15 years 1, 2
• Weak recommendation for annual LDCT screening for individuals aged 50-80 years with ≥20 pack-years smoking history who currently smoke or have quit within past 15 years (aligns with 2021 USPSTF update) 1, 3
• Screening should be discontinued once a person has not smoked for 15 years 2, 3
• Screening should be discontinued if the person develops health problems that substantially limit life expectancy or ability/willingness to undergo curative lung surgery 2, 3

Risk-Based Eligibility Criteria

• Individuals who don't meet standard age/smoking criteria but have high risk based on validated clinical risk prediction calculators may be considered for screening 1, 2
• Examples of risk thresholds that identify high-benefit individuals include:
  • ≥1.51% 6-year risk on PLCOm2012 calculator 1, 2, 4
  • ≥1.33% 5-year risk on LCDRAT calculator with ≥10 years life expectancy 1
  • ≥16.2 days life-gained on LYFS-CT calculator 1
• Risk-based approaches may improve screening efficiency and reduce disparities across race and sex 1, 4, 5

Contraindications for Screening

• Symptomatic individuals should not enter screening programs but instead receive appropriate diagnostic testing 1, 2
• Individuals with significant comorbidities limiting life expectancy or ability to tolerate treatment should not be screened 2, 3
• Screening is not recommended for individuals younger than 50 years or with less than 20 pack-years smoking history without additional risk factors 1, 3

Implementation of Screening Programs

• Screening programs should develop strategies to identify symptomatic patients who need diagnostic testing rather than screening 1
• Programs should define what constitutes a positive test based on nodule size (threshold of 4mm, 5mm, or 6mm in diameter) 1
• LungRADS structured reporting system uses 6mm threshold at baseline and 4mm for new nodules on annual scans 1
• Screening programs should develop strategies to maximize compliance with annual screening exams 1, 2
• A comprehensive approach to nodule management should include multi-disciplinary expertise (Pulmonary, Radiology, Thoracic Surgery, Medical and Radiation Oncology) 1, 2

Benefits and Harms of Screening

• Benefits: LDCT screening reduces lung cancer mortality and increases early-stage detection 6, 7
• In the SUMMIT study, 79.3% of screen-detected lung cancers were diagnosed at stage I or II, and surgical resection was the primary treatment in 77.0% of cases 7
• Potential harms include:
  • False positives (4.8% in the SUMMIT study) 7
  • Radiation exposure from repeated annual scans 2
  • Overdiagnosis of indolent cancers 2, 5
  • Complications from invasive diagnostic procedures 2

Important Caveats

• Smoking cessation counseling should be provided alongside screening; screening is not a substitute for smoking cessation 2
• Shared decision-making discussion with a qualified health professional should occur before initiating screening 6
• Recent evidence suggests that years since quitting may not need to be an eligibility criterion to begin or stop screening for former smokers 6
• Modeling studies suggest that screening individuals starting at age 50 or 55 through age 80 with 20+ pack-years smoking history results in more benefits than the 2013 USPSTF criteria 5, 3