Spatial Glioma Distribution and Development of Post-Radiation Injury: The Left Temporal Region

Abstract

PURPOSE/OBJECTIVE(S): Post-radiation injury, such as early pseudoprogression or late-onset radionecrosis, is a relatively common finding after high-dose radiotherapy and occurs in 20%-30% of glioma patients treated with cranial radiotherapy. This side effect often leads to a treatment dilemma, as it can be difficult to distinguish from tumor progression on MRI. Associated risk factors are radiation dose and chemotherapeutic treatment. However, not much is known about the role of tumor location in development of these lesions. Therefore, we aimed to explore the spatial distribution, in location as well as volume, of glioma in relation to development of post-radiation injury. MATERIALS/METHODS: In a retrospective database of 144 adult cases of histologically confirmed WHO grade II-IV supratentorial gliomas, we identified 73 patients who received first surgery in 2012 till 2014 with postoperative MRI within 3 days, and subsequent radiotherapy with a follow-up of at least 6 months. Tumors were manually delineated on pre-operative T1 contrast-enhanced (T1-CE) MRI and location and volume were registered. Among the 73 patients, 15 had tumors which were not delineable on T1-CE, due to lack of clear contrast enhancement, and were thus excluded. Post-radiation injury lesions were defined as new enhancements on CE-T1 MRI which stabilized or decreased after at least 3 months follow-up. These lesions were investigated with regard to pre-operative tumor location and size. Tumor location was investigated after transformation to MNI space and determined with the neuroanatomical atlas by Neuromorphometrics Inc. and subsequently classified by frontal, insular, parietal, temporal and occipital involvement of either hemisphere. RESULTS: Incidence of tumors with and without post-radiation injury lesions did not differ between hemispheres. When considering tumor location, however, involvement of the left temporal region was significantly associated with development of post-radiation injury (P = 0.012). Pre-operative volumetric tumor size was not associated with development of post-radiation injury. CONCLUSION: Tumor location may predispose for post-radiation injury, either by local processes or factors involving prior surgical treatment. Our study showed a significantly increased occurrence of post-radiation injury in the left temporal region. Thorough examination of the spatial distribution of tumors and subsequent complications might be useful in further exploring etiology and eventually guiding treatment decisions.