DISCUSSION
tumor, tumors, SRS
TUMOR, TUMORS, METASTASES
In recent years, SRS has been administered to patients to treat an increasing number of BM and minimize the negative impacts on quality of life and neurocognition often associated with WBRT. However, guidelines regarding the number of metastases that can be safely treated are lacking, and practice patterns vary widely across the globe.The dose of radiation delivered to normal brain tissue during SRS increases as the volume of the treated tumor increases (Table One limitation of our Gamma Knife‐based analysis is that our estimates may not be extrapolatable to other radiotherapy modalities such as linac‐based techniques (e.g., cones, volumetric‐modulated arc therapy [VMAT], tomotherapy, robotic methods, single isocenter multiple targets [SIMT]). Future studies might involve similar analyses based on alternative treatment approaches. Another study limitation is the creation of a simulation model from a single institution's SRS Treatment Database. Although the model includes 250 lesions, the dataset may not be representative of tumor locations and doses administered at other institutions. Finally, while the analyses performed in our study do not explicitly account for hippocampal avoidance techniques, the prescription dose to the treated brain is the same for both hippocampal‐sparing and standard WBRT.In sum, our results suggest that treating 12–13 tumors per day over 10 days would deliver the dose of radiation to healthy brain tissue typically associated with a standard course of WBRT. Clinical exploration of our findings is required in order to address logistical concerns (e.g., time required to treat several dozen lesions with SRS) and potential risks of avoiding WBRT (often administered to treat tumors that are not yet visible on imaging) in favor of short‐term follow‐up imaging and repeat SRS. As techniques designed to minimize the negative impacts on quality of life and neurocognition often associated with WBRT evolve, the differences in morbidity between these new approaches and SRS may narrow.