Radiation Pneumonitis

• Damage to lungs after radiation therapy
• Usually requires at least 4500 rads
  • Especially common if >6000 R given in 5-6 weeks
• Occurs more often if there is concurrent or later chemotherapy
  
  
• Pathologic phases
  
  
  • Exudative phase = edema fluid + hyaline membranes
  • Organizing phase
  • Fibrotic phase = interstitial fibrosis
    
    
• Time of onset
  
  
  • Usually at least 6 weeks up to 6 months after treatment
    
    
• Location
  
  
  • Confined to radiation portal

Radiation portal (right) with subsequent radiation pneumonitis (left image).

·       Acute Radiation Pneumonitis

o       Occurs within 1-8 weeks after radiation therapy

o       Pathology

§         Depletion of surfactant (1 week to 1 month later), plasma exudation, desquamation of alveolar + bronchial cells

o       Usually asymptomatic

o       When symptomatic

§         Nonproductive cough, shortness of breath, weakness, fever (insidious onset)

§         Acute respiratory failure (rare)

o       Changes usually confined to radiation portal

o       Patchy / confluent consolidation, may persist up to 1 month (exudative reaction)

§         Atelectasis + air bronchogram

§    Spontaneous pneumothorax (rare)
 

• CT findings of acute radiation pneumonitis
  
  
  • Homogeneous slight increase in attenuation (2-4 months after therapy)
  • Patchy consolidation (1-12 months after therapy)
  • Non-uniform discrete consolidation (most common; 3 months to 10 years after therapy)

Sequential transverse images through lung showing radiation pneumonitis in right lung 

• Prognosis
  
  
  • Recovery or progression to death from fibrosis
    
    
• Rx
  
  
  • Steroids

·       Chronic Radiation Damage

o       9-12 months after radiation therapy

o       Histology

§         Permanent damage of endothelial + type I alveolar cells

o       May be associated with:

§         Thymic cyst

§         Calcified lymph nodes (in Hodgkin disease)

§         Pericarditis + effusion (within 3 years)

§         Severe loss of volume

§         Dense fibrous strands from hilum to periphery

§         Thickening of pleura

o       CT findings

§         Solid consolidation (radiation fibrosis) + bronchiectasis (stabilized by 1 year after therapy) 

Radiation Fibrosis. There is a zone of increased density in the right paratracheal region with an almost straight edge (white arrows) suggestive of scarring from a radiation portal. The tr4achea is deviated to the right from volume loss (red arrow).

Radiation Fibrosis. The chest radiograph shows bilateral and almost symmetrical densities in a paramediastinal location with unusually well-demarcated edges, suggesting a radiation portal(white arrows). The CT scan demonstrates the same findings with fibrotic stranding seen on both sides of the mediastinum along the path of prior radiation (red arrows).