P11.11.A VOLUMETRIC AND SPATIAL ANALYSES OF TREATMENT-RELATED INJURY IN GLIOMA

Abstract

Abstract BACKGROUND As diffuse glioma cannot yet be cured, benefits of therapeutic strategies should be carefully balanced against their burden. Postoperative ischemia is a relatively common adverse event of surgery, which can lead to serious neurological deficits. Radiation therapy (RT) can cause post-RT lesions, which may cause clinical symptoms and can create a therapeutic impasse since they mimic tumor progression. We aimed to explore the spatial and volumetric tumor and treatment characteristics in relation to development of treatment-related effects in glioma. Materials and METHODS We retrospectively included 144 WHO grade II-IV supratentorial glioma cases, which were resected from 2012 till 2014 and had early postoperative MRI with diffusion-weighted imaging (DWI). Tumors were delineated on preoperative contrast-enhanced T1 MRI for high grade gliomas and FLAIR for low grade gliomas. Postoperative ischemia was defined as new, confluent diffusion restriction on postoperative DWI. Post-RT injury was investigated in patients who received RT after first surgery and had at least 6 months of follow-up (FU), and was defined as new or increasing contrast-enhancement that subsequently stabilized or decreased during FU. After manual delineation and non-linear registration to MNI stereotaxic space, all lesions were investigated with regard to size and location of pre-operative tumor, resection cavity, residual tumor and extent of resection (EOR). Voxel-based analysis (VBA) was performed with family-wise error correction for multiple comparisons. RESULTS Postoperative ischemia occurred in 93 of 144 cases and was associated with a larger EOR (P=0.02). Ischemic volume was correlated with a larger preoperative tumor volume (P=0.009) and resection volume (P=0.001). Post-RT injury was found in 25 of 67 analyzed cases and was associated with a larger residual tumor volume (P=0.021) and a smaller EOR (P=0.005). VBA showed an association of the occurrence of post-RT lesions with a cluster of preoperative tumor voxels in the left temporal lobe and clusters of residual tumor voxels in the left temporal and right frontal region. No association in volume or location was found between postoperative ischemia and post-RT lesions. CONCLUSION Adverse events of glioma treatment may be influenced by tumor and treatment volumes. In our population, a larger EOR was associated with the occurrence of postoperative ischemia, and larger tumor and resection volumes were correlated with the volume of ischemia. Additionally, the occurrence of post-RT injury was associated with a larger residual tumor and a smaller EOR, as well as a left temporal preoperative tumor location and a right frontal or left temporal residual tumor location. A thorough examination of spatial and volumetric characteristics of the tumor, treatment and subsequent complications can help elucidate the etiology and guide treatment decisions.