This is a phase II, single-arm, multi-center study assessing the feasibility and tolerance of WBRT using upfront PRDR in the treatment of solid tumor brain metastases. This study will also examine the impact of substituting PRDR for standard whole-brain radiation therapy in the upfront treatment of brain metastases on neurocognitive decline as compared to historical controls. Additionally, clinical patient outcomes associated with radiation treatment of brain metastases will be collected. Using a group sequential design with one interim analysis to stop for futility, the investigators will recruit and enroll 53 adult patients (≥18 years) undergoing upfront treatment of brain metastases to determine feasibility and a preliminary analysis after the first 27 enrolled patients.~In order to be eligible for this study, patients must have a biopsy-proven solid malignancy with intracranial lesions radiographically consistent with or pathologically proven to be brain metastases. Patient who are confirmed to meet all eligibility criteria will be registered to the study and start PRDR WBRT within two weeks postregistration. Patients will receive PRDR WBRT as a dose of 30Gy in 10 fractions and start memantine orally two days prior to (or one day prior to) but no later than the fourth PRDR WBRT treatment session.
Study patients will receive Whole-brain radiation therapy (WBRT) - pulsed reduced dose rate (PRDR) within 14 days of registration. All patients will receive single daily fractions using 3D conformal radiotherapy. A dose of 30 Gy in 10 fractions will be delivered using the PRDR technique.