David Palma MD, FRCPC, Presenter: Nothing to Disclose

Seth Jay Kligerman MD, Presenter: Author, Reed Elsevier

1) To review the differences between modern radiotherapy techniques vs. older radiation delivery methods, and the potential impact of these differences on post-treatment imaging. 2) To discuss the expected benign radiographic changes after stereotactic ablative radiotherapy for lung cancer. 3) To review recent data regarding the sensitivity and specificity of various imaging characteristics for distinguishing recurrence vs. fibrosis after stereotactic radiation.

Radiation therapy for lung cancer has undergone major changes over the past decade, with the use of four-dimensional CT scans for treatment planning, the introduction of intensity modulated radiation therapy, and the rapid adoption of stereotactic ablative radiatiotherapy. The changes in treatment designs and the use of have very large daily doses can result in patterns of radiation-induced lung injury (RILI) that may be difficult to distinguish from tumor recurrence. In some cases, patients have undergone 'salvage' surgical resection only to find fibrotic tissue, and conversely the opportunity for early detection of recurrence and possible salvage can be missed if recurrent tumor is not identified early in the post-treatment period. Classification systems exist for describing acute- and late-developing patterns of RILI on CT imaging after stereotactic radiotherapy. The identification of 'high risk features' (HRF) on CT for may allow for better discrimination of recurrence vs. fibrosis; these features will be reviewed. The use of PET/CT has demonstrated mixed results in identifying recurrence, but may plan a role when CT findings remain equiovcal.

Palma, D, Kligerman, S, Post-radiation Therapy Chest Imaging.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14002106.html