ARRS 2022 Abstracts

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E1305. I Danced Through Radiation Changes: Post-Radiation Changes Treatment of Lung Cancer - What to Except and Not to Except
Authors
  1. Anitha Kini; The Ottawa Hospital
  2. Elena Pena; The Ottawa Hospital
  3. Carole Dennie; The Ottawa Hospital
  4. Carolina Souza; The Ottawa Hospital
Background
Substantial changes in the lung tissue occur following 3D conformal radiation therapy (3D CRT) and stereotactic body radiation therapy (SBRT) for treatment of lung cancer. The purpose of this educational exhibit is to describe expected radiation-induced changes on CT of the chest and review the appearances that should raise suspicion for recurrence.

Educational Goals / Teaching Points
This exhibit aims to describe basic principles of radiation therapy in lung cancer that explain imaging appearances on CT of the chest following 3D CRT and SBRT, including expected temporal evolution of radiation-induced changes; review the spectrum of CT appearances of radiation-induced changes on CT in patients treated for lung cancer; and describe potential imaging pitfalls for local recurrence post-radiation as well as CT findings that should be considered suspicious for recurrence in this setting.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
The imaging appearance of radiation-induced changes in the lungs varies and evolves with the time elapsed after completion of therapy. Early changes of radiation pneumonitis manifest with consolidation and/or ground glass opacities with no substantial architectural distortion. Over time, radiation fibrosis occurs, manifesting with volume loss, distortion of the lung architecture and traction bronchiectasis along with chronic consolidation at times with mass- like appearance. Described CT features suspicious for local recurrence post-radiation include enlarging opacity with bulging margins and loss of pre-existing air bronchograms. FDG PET-CT may be helpful in the differentiation of metabolically active tumour and fibrosis.

Conclusion
Substantial changes occur in the lung tissue following radiation treatment for lung cancer. Recognition of expected CT appearances and abnormalities suspicious for local recurrence are essential to ensure appropriate care.