RADT-28. RADIATION DOSE-DEPENDENT LONG-TERM NEUROCOGNITIVE DECLINE IN LOW GRADE GLIOMA PATIENTS: RESULTS OF A CROSS-SECTIONAL STUDY

Abstract BACKGROUND Radiotherapy is a well-known risk factor for neurocognitive decline in glioma patients. Advanced radiotherapy techniques enable more selective brain irradiation. However, limited data exists on which brain regions are most relevant to avoid. The aim of this study was to explore the dose-effect relationship between brain subvolumes and neurocognitive performance. METHODS In this cross-sectional study, patients with grade II or III glioma treated with radiotherapy who were free of progression for at least one year were eligible. Patients underwent a neurocognitive test battery, including Rey Auditory Verbal Learning Test; (RAVLT), Trail Making Test (TMT), Copy of Rey’s Complex Figure Test (RCFT), Single Digit Modalities Test (SDMT) and Verbal Fluency tests (letters and categories). Test scores were correlated to radiation dose distributions in brain subvolumes using non-parametric tests. RESULTS The study was composed of 17 right-handed patients with grade II (n= 14) and grade III (n= 3) gliomas. The mean follow up after radiotherapy was 42 months, and the mean age 47 years. Performance on all tests was significantly worse for patients compared to healthy matched controls. Correlations were found between: 1) dose to the left hippocampus and performance on the RAVLT (Delayed Recall) (r= -0.60; p= 0.011); 2) dose to the supratentorial brain and performance on the TMT-A (r= 0.54; p= 0.025) and 3) dose to the left hemisphere and SDMT (r= -0.64; p= 0.006) and verbal fluency tests (for letters score: r= -0.73; p= 0.001). CONCLUSIONS We found significant correlations between radiation dose to the left hippocampus and hemisphere and neurocognitive performance. In this small sample we could not account for the effect of tumor location as a confounder. Reducing radiation dose to the left hippocampus and hemisphere by using advanced radiotherapy techniques may give superior neurocognitive outcomes.