WE-E-BRA-03: MR Functional Imaging to Guide Radiotherapy: Opportunities and Challenges in the Clinic

Human tumors are characterized by an abnormal vascular network that develops because of unregulated angiogenesis. This contributes to abnormalities of the tumor microenvironment like hypoxia, acidosis and high interstitial fluid pressure that influence treatment response and patient survival. There is an important clinical need to develop new minimally invasive tools for characterizing the tumor microenvironment at diagnosis, and monitoring changes during treatment with radiotherapy, chemotherapy or new biologically targeted drugs. MR-based imaging approaches offer exciting possibilities that have yet to be fully exploited. Dynamic contrast enhanced (DCE) MR allows the functional characteristics of the tumor vasculature to be interrogated serially over time. Studies in human cancers have shown substantial differences in DCE MR parameters between tumor and normal muscle in keeping with higher blood flow and vascular permeability. DCE MR has been shown to correlate with response to radiotherapy or drugs that specifically target the tumor vasculature. However, despite important advances, MR functional imaging has not been adopted in routine clinical practice, in part because of a lack of consensus on optimal imaging techniques, analysis methods and reporting metrics. Further refinement and standardization is required founded on interdisciplinary collaboration among clinicians, medical imagers, biologists, physicists and mathematicians to make these techniques robust and clinically applicable.

1. Discuss the clinical use of MR functional imaging in patients receiving radiotherapy and the challenges to wide-spread clinical utilization. 2. Discuss the value of MR functional imaging as a predictor of clinical outcome in patients receiving radiotherapy, and a means of monitoring biologic response over a course of fractionated treatment. 3. Understand the role of MR functional imaging in the evaluation of new treatment strategies comprised of radiotherapy and drugs that specifically target the tumor vasculature.