screening for lung cancer

Epidemiology

• among 3400 people who received CT scans for lung cancer screening
  • only 21% met all 3 USPSTF eligibility criteria
  • 20% met none of the criteria
  • the rest met only one or two criteria.
• among 5800 people who met all 3 USPSTF criteria, only 13% received CT screening

Indications

• USPSTF & ACA recommend annual screening with low-dose CT (LDLCT) for current or past smokers age 50-80 with a 20-pack-year smoking history
  • formerly 30 pack-year age 55-74 years who currently smoke or have quit within the past 15 years
  • formerly insufficient evidence to recommend routine screening
  • high-risk adults with negative CT screen for lung cancer might not require subsequent annual screening (not standard of care)
• screening those at highest risk yields highest benefit/harm ratio
  • low-dose spiral CT anually for screening high-risk patients
  • screen smokers & former smokers age 55-74 with >=30 pack-years of smoking
• some controvery still exsits, especially in < highest risk patients
  • no reduction in mortality in 20 year follow-up analysis
  • overdiagnosis & potentially harmful workup of benign lesions is a concern
• screening with low-dose CT reduces risk in older smokers
  • American Lung Association & American Association for Thoracic Surgery, & American Cancer Society (ACA) now recommend screening for high-risk patients
    • current or former smoker with >= 20 pack-year history of smoking
    • age 55-79 years (contrast with CMS proposal)
    • age 55-77 years (American College of Chest Physicians)
    • age 50-80 years (USPSTF & ACA)
    • long-term lung cancer survivors until age 79
  • number needed to screen to prevent 1 lung cancer related death ~ 320
  • substantial uncertainty
    • harm from overdiagnosis & radiation remain unresolved
    • positive predictive value of abnormal CT = 4%
• annual chest X-ray does not diminish mortality from lung cancer

* a 55 year old current smoker with a 30 pack-year history of smoking has a higher risk of false positives than a 74 year old current smoker with a 60 pack-year history of smoking, therefore would benefit less from screening

Contraindications

• significant medical problems affecting life expectancy
• non smokers or former smoked who quit > 15 years ago
• asymptomatic smokers & former smokers who do not meet the smoking & age criteria
• patients with symptoms suggestive of lung cancer should receive appropriate diagnostic testing not screening

Benefit/risk

• sensitivity 93%, specificity 84%
• positive predictive value 10%, negative predictive value 99.8%
• number needed to treat (screen) to prevent 1 death
  • 217, 142, 194 (USPSTF guidelines)
  • models based on risk 162
  • 100
• number needed to harm
  • 4 for false positive CT scan
  • 2 for false positive CT scan with repeat scanning
  • 30 for unnecessary surgery
  • 50 for unnecessary invasive procedures (bronchoscopy, thoracotomy)
  • 161 for surgical complication
• lower quit rates among smokers who have been screened
• no statistically significant effects of CT screening on lung cancer mortality
  • high-risk subgroup analyses showed nonsignificant trends
• after 10 years of screening, one radiation-induced cancer for every 108 lung cancers detected
• 67% of the screen-detected cancers were overdiagnosis in Danish Lung Cancer Screening Trial vs 19% in U.S.-based National Lung Cancer Screening Trial
• indeterminate scans requiring additional imaging 20% [53}
• no reduction in overall mortality
  • early-stage diagnoses & all-cause survival have increased since 2014, after CT screening was recommended for high-risk patients
    • advances in treatment & lead-time bias may contribute to the increase in survival

Adverse effects

• radiation exposure
  • lifetime risk of radiation-induced cancer from screening is 2.6-8.1 per 10,000

Procedure

• 4 protein biomarkers for lung cancer screening may identify patients who would benefit from low-dose chest CT
• low-dose chest CT

* threshold for a positive test is a nodule 4-6 mm in diameter

Radiology

• low-dose chest CT (LDLCT)
  • respiratory bronchiolitis-associated interstitial lung disease found in active smokers with centrilobular micronodules
  • aortic valve calcification may represent aortic valvular stenosis

Complications

• 1/3 of patients undergo further imaging
• 1/35 patients undergo invasive procedures (biopsy, bronchoscopy, mediastinoscopy ...)
  • procedural complications
    • intestinal obstruction
    • cardiac arrest
    • acute respiratory failure

Management

• see solitary pulmonary nodule

Comparative biology

• polymer nanoparticles coated in DNA targeted by protease enzymes linked to stage I lung adenocarcinoma are administered by nebulizer or inhaler
• proteases cleave off the DNA which enter the bloodstream & are secreted in the urine
• a test strip can detect the DNA, with results ~20 minutes
• tested in mice with specificity of 100%, sensitivity 85%

Notes

• CMS announces Medicare coverage for lung cancer screening in high-risk patients
  • age 55-77 years
  • >=30 pack-year history of smoking
  • current smoker or has quit within last 15 years
  • a written order from a clinician obtained during a lung cancer screening counseling & shared decision-making visit, which includes information on the procedure's risks & benefits
• screening reduces risk of death from lung cancer by 20% in proposed Medicare-covered population
• cost per quality-adjusted life-year gained is $81,000 for CT screening in high-risk patients
• no mortality benefit of annual low-dose spiral CT in high-risk patients in a community setting
• discourse on significance of threshold for positive CT
• risk of overdiagnosis
• Medicare advisers previously voted against paying for lung cancer screening in high-risk patients
• higher rate of false positive (27% vs 22%) for patients > 65 vs < 65 years of age
• Lung-RADS criteria for classifying lung nodules detected during low-dose computed tomography screening increased specificity at the cost of decreased sensitivty for detecting lung cancer
• decline in cases with a 30-pack-year smoking history who had quit within 15 years
• contents of lung cancer screening medical websites emphasize potential benefits while downplaying potential harms

More general terms

• screening for cancer

Additional terms

• biomarkers for lung cancer screening
• lung cancer

Patient information

screening for lung cancer patient information