Differential Diagnosis Relapse/radiation Necrosis after M3 Brainlab-radiosurgery Using Iplan Stereotaxy Software

Brain metastases are the most common intracranial tumors, with an incidence of about 150 000 new cases per year in the US. Radiosurgery is increasingly used as the first line treatment of these lesions because it achieves a high local control rate (95%) with relatively little side effects, such as radiation necrosis (5-15%) 2, . Differential diagnosis between tumor relapse and radiation necrosis might be difficult to realize because, in both cases, MRI pattern is characterized by an increased gadolinium contrast-enhancement 5, 11, . Nevertheless, one must aim to make an accurate and precise diagnosis because it might highly influence the treatment strategy. This can range from a „wait and see‟ approach with corticosteroids in case of radiation necrosis as opposed to surgery. Or, in case of a tumor relapse, a second radiosurgery might be necessary . Tyrosine-PET examination might be a non-invasive alternative valuable for this diagnosis because of its high specificity for tumoral tissue 4, 6, 9-10, 12-14, . The goal of this protocol is to compare results of a non-invasive strategy, including MRI with multiple modalities and Tyrosine-PET with the “gold standard” histopathology study. This correlation is performed using a stereotactic biopsy realized with the Brainlab iPlan Stereotaxy software.