Posted: Monday, September 11, 2023
Stereotactic radiosurgery may be an effective treatment of brain metastasis. In addition, extracranial radiotherapy may induce antitumor immune responses. Given these findings, Joseph Sia MD, of the Peter MacCallum Cancer Centre, Melbourne, Australia, and colleagues sought to investigate the tumor microenvironment of brain metastasis in patients with HER2-positive breast cancer treated with this type of surgery. Presented at the 2023 joint Society for Neuro-Oncology (SNO)/American Society of Clinical Oncology (ASCO) CNS Cancer Conference (Abstract BSBM-15), their study suggested the presence of both systemic and local immunologic changes in these patients who received stereotactic radiosurgery.
Blood and bone marrow samples were examined from 10 patients with HER2-positive breast cancer who were enrolled in the TROG 16.02 translational substudy for immunologic effects of stereotactic radiosurgery (ACTRN12616001265460). Blood samples were taken before and 7 to 14 days after radiosurgery from intact HER2-positive brain metastasis or from resected cranial cavities. These samples were analyzed by flow cytometry to look for immune cell and cytokine modulation.
Monocytes, CD8-positive memory, and regulatory T cells were enriched in the blood after stereotactic radiosurgery, and conventional dendritic cells and CD4-positive T cells were diminished. Immunohistochemistry also corroborated the influx of CD68-positive macrophages and CD3-positive T cells into tumor and brain regions after radiosurgery. The authors postulated that a radiation-induced adaptive immune response (involving the monocyte-macrophage lineage as antigen-presenting cells) may have been initiated intracranially and suggest further study to confirm their findings.
Disclosure: The study authors reported no conflicts of interest.