Neurofilament light and glial fibrillary acidic protein do not reflect neuronal or glial damage during different intracranial radiotherapy regimes: a pilot study

Introduction: Neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP) have been shown to be non-specific markers of central nervous system damage and have been associated with the occurrence of primary or secondary brain tumours. However, the response of these markers to cerebral radiotherapy has not been explored to date. Methods: In this pilot study, we measured NfL and GFAP levels before, during, and after radiotherapy, as well as during follow-up, in a representative clinical cohort of patients treated with percutaneous radiotherapy either for single or multiple brain metastases, for glioblastoma, or with whole-brain irradiation. Results: We confirmed elevated NfL and GFAP levels in all patients before the start of radiotherapy. A significant increase after the onset of radiotherapy was not observed. During long-term follow-up, most cases of decreasing NfL and GFAP values correlated with treatment response, whereas the most pronounced increases in serum NfL levels were followed by the detection of several new cerebral lesions. Conclusion: Cerebral radiation injury does not appear to correlate with increased NfL and GFAP levels during radiotherapy. After treatment, NfL and GFAP remain suitable candidates for follow-up and possibly for the early detection of new lesions.