Evaluating Changes to Blood-Brain Barrier Integrity in Brain Metastasis over Time and after Radiation Treatment.
BACKGROUND
The incidence of brain metastasis due to breast cancer is increasing, and prognosis is poor. Treatment is challenging because the blood-brain barrier (BBB) limits efficacy of systemic therapies. In this work, we develop a clinically relevant whole brain radiotherapy (WBRT) plan to investigate the impact of radiation on brain metastasis development and BBB permeability in a murine model. We hypothesize that radiotherapy will decrease tumor burden and increase tumor permeability, which could offer a mechanism to increase drug uptake in brain metastases.


METHODS
Contrast-enhanced magnetic resonance imaging (MRI) and high-resolution anatomical MRI were used to evaluate BBB integrity associated with brain metastases due to breast cancer in the MDA-MB-231-BR-HER2 model during their natural development. Novel image-guided microirradiation technology was employed to develop WBRT treatment plans and to investigate if this altered brain metastatic growth or permeability. Histology and immunohistochemistry were performed on whole brain slices corresponding with MRI to validate and further investigate radiological findings.


RESULTS
Herein, we show successful implementation of microirradiation technology that can deliver WBRT to small animals. We further report that WBRT following diagnosis of brain metastasis can mitigate, but not eliminate, tumor growth in the MDA-MB-231-BR-HER2 model. Moreover, radiotherapy did not impact BBB permeability associated with metastases.


CONCLUSIONS
Clinically relevant WBRT is not curative when delivered after MRI-detectable tumors have developed in this model. A dose of 20 Gy in 2 fractions was not sufficient to increase tumor permeability such that it could be used as a method to increase systemic drug uptake in brain metastasis.
Imaging Research Laboratories, Robarts Research Institute, London, ON, Canada; Department of Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada. Electronic address: dmurrell@robarts.ca.
Donna H
DH
Murrell
Department of Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada. Electronic address: nzargham@uwo.ca.
Niloufar
N
Zarghami
Department of Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada. Electronic address: mjensen4@uwo.ca.
Michael D
MD
Jensen
Department of Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada; London Regional Cancer Program, London Health Sciences Centre, London, ON, Canada. Electronic address: Ann.Chambers@lhsc.on.ca.
Ann F
AF
Chambers
Department of Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada; London Regional Cancer Program, London Health Sciences Centre, London, ON, Canada. Electronic address: ewong4@uwo.ca.
Eugene
E
Wong
Imaging Research Laboratories, Robarts Research Institute, London, ON, Canada; Department of Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada. Electronic address: pfoster@robarts.ca.
Paula J
PJ
Foster