The concept is that WBRT with SIB would be expected to maximize both local and in-brain distant control as has already been shown in studies exploring WBRT with SRS boost. However, by itself WBRT with SIB does not address the concern over neurocognitive outcomes. Therefore, investigators hypothesize that there is a lower WBRT dose threshold that will maintain acceptable in-brain distant control, particularly in the setting of a SIB to gross lesions to maintain treated lesion control. In addition, lower overall brain dose (including lower hippocampal dose without specific hippocampal avoidance) may potentially improve neurocognitive function. Investigators are also interested in evaluating treated lesion control, overall survival, neurocognitive sequelae of therapy, quality of life, performance status, and adverse effects of therapy. Biomarker identification for potential correlative circulating tumor DNA and microRNA is an exploratory endpoint to generate data for future prospective evaluation.