Radiosurgery for small-cell lung cancer brain metastases: a review

First-line stereotactic radiosurgery (SRS) is now considered the preferred treatment over whole brain radiation therapy (WBRT) for limited brain metastases arising from most tumor histologies. This standard was reached following the consistent results of multiple phase III studies which demonstrated that, despite improved CNS control, the addition of WBRT to SRS does not improve overall survival (OS) and is associated with a reduction in cognitive function. Thus, it may be reasonable to consider the benchmark necessary to favor a paradigm of SRS alone over strategies incorporating WBRT as the demonstration of comparable OS in the context of decreased treatment-related side effects. However, patients with small-cell lung cancer (SCLC) brain metastases were excluded from the landmark trials that established SRS alone for limited brain metastases, largely due to concerns for short-interval CNS progression in SCLC as well the historic role of prophylactic cranial irradiation (PCI) in SCLC in the absence of known brain metastases. As a result, WBRT has remained the standard for SCLC for limited and even solitary brain lesions. With shifting SCLC care patterns including increased MRI surveillance, decreased PCI delivery, and emerging systemic agents, interest in first-line SRS for SCLC is likely to continue to increase over time. Herein we will review the emerging data for first-line SRS in the management of SCLC brain metastases and the potential for its increasing role in the setting of a greater utilization of MRI surveillance and improving systemic therapies.