A Pilot Phase 2 Study Evaluating Dose De-escalation in Whole Brain Radiation Therapy With Simultaneous Integrated Boost for Patients With Brain Metastases

This trial is a pilot, Phase 2, sequential two-cohort study designed to test two de-escalated whole brain radiation therapy (WBRT) dose levels and assess their ability to maintain acceptable in-brain distant control. The WBRT dose would decrease as the study moves forward, both in terms of absolute value and equivalent dose in 2 Gray fractions (EQD2) (as determined by the linear quadratic radiobiological model). The absolute value of the simultaneous integrated boost (SIB) dose will change with each dose level because the number of fractions delivered will depend on the WBRT dose. As such, the SIB dose will be manipulated such that the EQD2 will remain essentially equivalent despite the difference in the number of fractions delivered. This design will ensure that the only variable is the change in WBRT dose.

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.