Integration of immuno-oncology with stereotactic radiosurgery in the management of brain metastases.

Abstract

Brain metastases traditionally carried a poor prognosis with treatment being a combination of surgery, whole-brain radiation therapy, and glucocorticoids; however, this treatment paradigm carried a significant amount of morbidity. In recent years, stereotactic radiosurgery (SRS), which involves the delivery of a highly conformal dose of radiation over a single session, has been shown to be an effective alternative to WBRT with excellent rates of local control and improved quality of life; however, a survival benefit has not been demonstrated. Recent developments have challenged the traditional view of the central nervous system being "immunologically privileged" which has led to a greater focus on treating these patients with systemic therapies. Immune checkpoint inhibitors (ICI) have been shown to improve survival in multiple malignancies. As a result, there has been increased utilization in combining these therapies in this setting. We conducted a literature search of medical databases (e.g. PubMed) for articles involving the use of immune checkpoint inhibitors and stereotactic radiosurgery in managing brain metastases. Published evidence utilizing SRS and ICI is largely limited to single institution and retrospective in nature with the most common histology being melanoma. Combination therapy with SRS and ICI appears to improve survival in patients with brain metastases. The available data are largely retrospective; therefore, ongoing and planned prospective studies are needed to further validate these findings.