Lung-RADS

Lung-RADS^TM (or lung imaging reporting and data system) is a classification proposed to aid with findings in low-dose CT screening exams for lung cancer. The goal of the classification system is to standardize follow-up and management decisions. The system is similar to the Fleischner criteria but designed for the subset of patients intended for low-dose screening studies.

Classification system

Category 0 (incomplete)

• prior CT studies were performed, but are not available for comparison
• lungs are incompletely imaged

Category 1 (negative, <1% chance of malignancy)

• no lung nodules
• lung nodule(s) with specific findings favoring benign nodule(s)
  • complete calcification
  • central calcification
  • popcorn calcification
  • calcification in concentric rings
  • fat-containing nodules

Category 2 (benign appearance, <1% chance of malignancy)

• solid nodule(s)
  • <6 mm at baseline
  • new nodule <4 mm
• subsolid nodule(s)
  • <6 mm on baseline screening
• ground glass nodule(s)
  • <20 mm
  • ≥20 mm and unchanged or slowly growing
• category 3 or 4 nodules that are unchanged for ≥3 months

Category 3 (probably benign, 1-2% chance of malignancy)

• solid nodule(s)
  • ≥6 mm to <8 mm at baseline
  • new nodule 4 mm to <6 mm
• subsolid nodule(s)
  • ≥6 mm total diameter with solid component <6 mm
  • new <6 mm total diameter
• ground glass nodule(s)
  • ≥20 mm on baseline CT or new

Category 4A (suspicious, 5-15% chance of malignancy)

• solid nodule(s)
  • ≥8 mm to <15 mm at baseline
  • growing nodule(s) <8 mm
  • new nodule 6 mm to <8 mm
• subsolid nodule(s)
  • ≥6 mm total diameter with solid component >=6 mm to <8 mm
  • new or growing <4 mm solid component
• endobronchial nodule

Category 4B (suspicious, >15% chance of malignancy)

• solid nodule(s)
  • ≥15 mm at baseline
  • new or growing, and ≥8 mm
• subsolid nodule(s)
  • solid component ≥8 mm
  • new or growing ≥4 mm solid component

Category 4X (suspicious, >15% chance of malignancy)

• category 3 or 4 nodules with additional features or imaging findings that increase the suspicion of malignancy
• includes:
  • spiculation
  • ground glass nodule(s) that double in size in 1 year
  • enlarged regional lymph nodes

Modified categories

• [X]S (e.g. "3S") if there is a clinically significant or potentially significant non-lung cancer finding
• [X]C (e.g. "3C") for a patient with a prior diagnosis of lung cancer who returns to screening

Recommended follow-up

Category 0:

• comparison with prior studies before assignment of Lung-RADS classification

Category 1: 

• continue annual screening with LDCT

Category 2: 

• continue annual screening with LDCT

Category 3: 

• 6-month follow-up with LDCT

Category 4A: 

• 3-month follow-up with LDCT
• PET/CT may be used if there is a ≥8 mm solid component

Category 4B and 4X: 

• chest CT with or without contrast, as appropriate
• PET/CT and/or tissue sampling depending on the probability of malignancy and comorbidities (PET/CT if solid component ≥8 mm)

Practical points

• nodule measurement should be in lung windows
• nodule average diameter is rounded to the nearest whole number
• only a single measurement is necessary for round nodules
• "growth" is an increase in size of ≥1.5 mm
• assignment of a Lung-RADS status is based on the most suspicious nodule
• category 4B management is based on multiple factors including overall patient status and patient preference