NCOG-14. HIPPOCAMPAL N-ACETYLASPARTATE CONCENTRATION CORRELATES TO VERBAL MEMORY BEFORE RADIOTHERAPY FOR BRAIN METASTASES

Changes of quality of life and cognitive function, especially verbal memory, after brain radiotherapy is currently widely discussed in neurooncology with substantial change in the paradigm of treatment of brain metastases. In our previous study, we described the decrease in the hippocampal concentration of N-acetylaspartate (NAA, marker of neuronal density and viability) in response to whole brain radiotherapy (WBRT). The aim of presented analysis is to evaluate the NAA concentration before radiotherapy and to describe the relation to the verbal memory baseline. MATERIAL AND

Patients with brain metastases indicated to WBRT underwent hippocampal MR spectroscopy (MRS) along with neuropsychological examinations focused among others to verbal memory. Absolute NAA concentrations for right and left hippocampus and the sum of absolute NAA concentrations in both hippocampi were compared with results of AVLT_TR.

The examination was performed in 26 patients. Patients were divided into two groups based on median NAA concentration (8.56 mM). The median AVLT_TR was 37 points in the group with hippocampal NAA concentration ˂ 8.56 mM. In the group of patients with baseline NAA concentration ≤ 8.56 mM, the median AVLT_TR was higher with 43 points (Mann-Whitney U Test, p = 0.02).

Non-invasive examination by hippocampal MRS can predict the baseline pre-radiotherapy cognitive functions, which are normally tested by time-consuming psychological tests. Patients who had lower baseline NAA hippocampal concentrations had a significantly lower baseline verbal memory. NAA hippocampal concentrations may be a useful biomarker for selecting patients who would benefit most from the hippocampal sparing radiotherapy techniques reducing the risk of iatrogenic deterioration of QoL in patients treated with a palliative intent, especially in cases where local brain stereotactic radiotherapy is not applicable or available.

Supported by the Ministry of Health of the Czech Republic, grants NV18-03-00469, NV18-03-00398.