E2073. Spectrum of Imaging Findings in Radiation Therapy for Lung Cancer
  1. Divya Yadav; Sinai Grace Hospital
  2. Kelly Trinh; Texas Tech University Health Sciences Center
  3. Andy Yu; University of Texas MD Anderson Cancer Center
  4. Chad Strange; University of Texas MD Anderson Cancer Center
  5. Jitesh Ahuja; University of Texas MD Anderson Cancer Center
  6. Mylene Truong; University of Texas MD Anderson Cancer Center
  7. Pauline Truong; British Columbia Cancer Agency
Radiologic manifestations of lung injury following radiation therapy (RT) generally have a typical appearance and temporal evolution that are in part dependent on the radiation delivery technique used. Radiologic manifestations following high precision radiation therapy such as 3D conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT), stereotactic body radiotherapy (SBRT), and proton therapy (PT) tend to be similar to those of conventional RT; although, there are important differences in appearance and temporal evolution. Knowledge of the spectrum of the manifestations of radiation-induced lung injury that occur with conventional RT and high-precision dose radiotherapy and an understanding of the differences in manifestations and temporal evolution between these different techniques facilitate appropriate interpretation of imaging studies. This exhibit discusses factors that affect the development and severity of radiation-induced lung injury and the radiologic manifestations of radiation-induced injury with an emphasis on the differences that occur when conventional RT and high-precision dose radiotherapy techniques are used to treat lung cancer.

Educational Goals / Teaching Points
Discuss how high-precision dose techniques such as 3D-CRT, IMRT, SBRT and PT enable delivery of a larger therapeutic dose to the tumor, decreased radiation dose to normal tissue and improved local tumor control rate without the need for protracted fractionation. The demonstrate how the radiation delivery system, volume of lung radiated, dose and fractionation of radiation affect the development and severity of radiation-induced lung injury. To discuss the spectrum of imaging findings of radiation-induced lung injury from the acute phase (radiation pneumonitis) to the chronic phase (radiation fibrosis).

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
With conventional RT, most of the fibrosis will develop within the first 12 months. The fibrotic changes commonly show slow progression in the 6 to 12 months after completion of RT and usually stabilize within 2 years. With SBRT, the severity of the fibrotic phase peaks at 1 - 2 years, and evolution of the radiologic findings can occur more than 2 years after RT completion. Radiation-induced fibrosis, due to high precision RT, can manifest as a modified conventional pattern (consolidation, volume loss, and bronchiectasis similar to but less extensive than radiation fibrosis seen with conventional RT), scar-like pattern (linear opacity in the region of the original tumor) and mass-like pattern (focal opacity confined to the site of the original tumor). Imaging of the complications of RT include radiation recall pneumonitis, in situ pulmonary artery thrombosis, tumor recurrence, and secondary malignancies.

Knowledge of the radiation technique, radiation treatment plan, expected temporal evolution of radiation-induced lung injury, and concurrent chemoradiotherapy and or immunotherapy, are important to correctly identify the expected radiologic manifestations of radiation-induced lung injury and differentiate them from tumor recurrence or infection.