Pia C. Sundgren
Advanced MR imaging for monitoring response to treatment of brain tumors
Glioblastoma is the most common primary brain tumor. Due to ineffective therapy the prognosis of gliomblastoma is poor, and has driven research to find new therapeutic agencies. New treatment strategies for glioblastoma multiforme (GBM) have prolonged survival. For example the combination of temozolomide and radiation significantly prolongs survival compared with radiation alone and has become standard treatment for GBM. In addition, a new treatment strategy with Bevacizumab (Avastin), a humanized monoclonal antibody against VEGF, has been suggested. However despite advanced neuroimaging techniques it remains difficult to predict tumor response to anti-angiogenic therapy in individual patients. For example there is diminished contrast enhancement of the tumor and reduced surrounding edema most likely due to inhibition in vessel permeability early in the treatment with bevacizumab. This finding is named ”pseudoresponse” since the decreased enhancement can be secondary to an anti-permeability effect rather than the result of reduction in tumor size. The opposite is seen in the treatment with termozolamide and radiation where an increase in area of enhancement is seen that resolves over time - so called pseudoprogression. While pseudoprogression and pseudoresponse occur early during ongoing treatment, radiation injury or necrosis might be seen much later during follow up scanning and remains a diagnostic dilemma. Different MR imaging methods are used such as MR spectroscopy, Dynamic susceptibility contrast enhanced MRI imaging; new imaging analyzing methods like functional parametric response maps are also used in an attempt to separate these entities and improve the monitoring of patients undergoing treatment. The present lecture will focus on present knowledge and research in the use of advanced imaging to support response or progression during ongoing therapy, and to differentiate late treatment effects such as radiation injury from recurrent tumor. New analyzing methods, so-called parametric response maps used to predict clinical outcome parameters for treatment response will also be presented. About the speaker Sundgren uses advanced MRI techniques such as diffusion, MR spectroscopy and MR perfusion to study and monitor various diseases, especially brain tumors, autoimmune diseases such as SLE and various pain conditions.