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

Aim: 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. Methods: 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. Results: Published evidence utilizing SRS and ICI is largely limited to single institution and retrospective in nature with the most common histology being melanoma. Conclusion: 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.