# Increased Blood Levels of NfL, GFAP, and Placental Growth Factor After Radiotherapy to the Brain

## TL;DR

This study found that brain radiotherapy increases blood levels of proteins linked to nerve and brain cell damage in lung cancer patients.

## Contribution

The study shows that radiotherapy independently increases blood levels of NfL and GFAP, regardless of blood-brain barrier function.

## Key findings

- Serum NfL and GFAP levels increased after brain radiotherapy.
- Serum NfL correlated with cerebrospinal fluid NfL, independent of blood-brain barrier function.
- Serum placental growth factor levels also increased and correlated with the albumin ratio.

## Abstract

In this study, we analyzed biomarkers of neuronal, glial, and vascular injury in longitudinal paired samples of blood and cerebrospinal fluid after prophylactic cranial irradiation in patients with small cell lung cancer. Neurofilament light chain protein (NfL) and glial fibrillary acidic protein (GFAP) increased in serum and cerebrospinal fluid after irradiation; serum NfL correlated with cerebrospinal fluid values, apparently independent of blood–brain barrier function, whereas GFAP correlations were weaker. Although several patients developed brain metastases, linear mixed model results were consistent with an independent effect of radiotherapy on serum NfL and GFAP. Serum placental growth factor also rose and correlated with the albumin ratio. Our results support a radiotherapy‐associated increase of NfL and GFAP in blood.