From the Guidelines
The typical radiological pattern of radiation pneumonitis is characterized by airspace and interstitial edema, proceeding to poorly defined consolidation, and evolutional changes to radiation fibrosis, as described in the 2021 position paper from the Fleischner Society 1.
Key Radiological Features
- Airspace and interstitial edema
- Poorly defined consolidation
- Evolutional changes to radiation fibrosis
- These changes typically appear 3-12 weeks after irradiation, as noted in the study 1
Distribution and Progression
- The pattern is often confined to the radiation field, with changes corresponding to the geometric shape of the radiation portal
- The distribution is typically non-segmental and does not follow anatomical boundaries
- As the condition evolves into fibrosis, traction bronchiectasis, architectural distortion, and volume loss become more prominent, as described in the study 1
Diagnostic Considerations
- High-resolution CT is more sensitive than chest radiography for detecting these changes
- Understanding this pattern is crucial for differentiating radiation pneumonitis from other conditions such as infection, recurrent malignancy, or drug-induced pneumonitis, as discussed in the 2021 position paper from the Fleischner Society 1
From the Research
Radiological Patterns of Radiation Pneumonitis
The typical radiological pattern of radiation pneumonitis can be characterized by several features, including:
- Ground-glass opacities
- Consolidation
- Septal thickening
- Traction bronchiectasis
- Pulmonary nodules
- Mosaic attenuation on inspiratory images and air trapping on expiratory CT images 2
- Reticulation due to fibrosis superimposed on findings of subacute hypersensitivity pneumonitis 3
Classification of Radiation Pneumonitis Patterns
Radiation pneumonitis can be classified into three patterns:
- Localized pneumonia (LP)
- Cryptogenic organizing pneumonia (COP)
- Acute interstitial pneumonia (AIP) 4 These patterns exhibit different severities in clinical outcomes, with AIP patterns associated with higher CTCAE grade and fewer days between the start of RT and the onset of RP 4
CT Findings and Clinical Outcomes
CT findings of radiation pneumonitis are related to clinical outcomes, with underlying pulmonary fibrosis, AIP pattern, and higher CT extent scores associated with higher CTCAE grade 4 Age, bilateral distribution, RT-RP days, and CT extent score ≥3 are independent predicting factors for higher CTCAE grade 4