Stereotactic Radiosurgery (SRS) Dose-Escalation Study for Brain Metastasis

Recently, several large randomized studies have shown that in patients with limited brain metastases, whole brain radiation can be safely deferred when treated with SRS and close surveillance. In light of this, most of such patients are now treated with SRS alone without WBRT. However, the SRS doses set by Radiation Therapy Oncology Group (RTOG) 90-05 continue to be applied to patients without previous cranial irradiation. The potential insufficiency of current SRS dose for long-term tumor control is of pressing concern. The advances chemotherapy has led to an improvement in overall survival in many patients with metastatic cancer, including malignancies often associated with brain metastases, such as lung (40-50%) and breast (15%). As these patients survive longer, more patients may develop brain metastases and the current dose of SRS may not be adequate to control the brain metastases for the duration of their survival. In fact, there is evidence that the control rate declines with time after SRS, and after 3 years, the local control rate may be only about 60%. In the case of brain metastases from relatively radio-resistant melanoma, the reported 12-months local control rates for SRS range from 52% to 75%. More potent SRS doses could lead to improved long-term control of brain metastases.