Memantine Hydrochloride and Whole-Brain Radiotherapy With or Without Hippocampal Avoidance in Reducing Neurocognitive Decline in Patients With Brain Metastases

Inclusion Criteria: * PRIOR TO STEP 1 REGISTRATION: * Brain metastases outside a 5-mm margin around either hippocampus must be visible on contrast-enhanced magnetic resonance imaging (MRI) performed =\< 21 days prior to Step 1 registration; an allowed exception, regarding ability to image brain metastases, would be that patients who had undergone radiosurgery or surgical resection and are planning adjuvant WBRT do not have to have visible disease but do need a pre-surgery MRI or computed tomography (CT) scan demonstrating brain metastases; however, the brain metastases could not have been within 5 mm of either hippocampus * Patients must have a gadolinium contrast-enhanced three-dimensional spoiled gradient (SPGR), magnetization-prepared rapid gradient echo (MP-RAGE), or turbo field echo (TFE) axial MRI scan with standard axial and coronal gadolinium contrast-enhanced T1-weighted sequence and axial T2/FLAIR sequence acquisitions; to yield acceptable image quality, the gadolinium contrast-enhanced three-dimensional SPGR, MP-RAGE, or TFE axial MRI scan should use the smallest possible axial slice thickness not exceeding 1.5 mm; the associated coronal and sagittal contrast-enhanced T1 sequences can be up to 2.5 mm in slice thickness; this MRI must be obtained =\< 21 days prior to step 1 registration; the vendor specific MRI protocols are available for download from the Alzheimer's Disease Neuroimaging Initiative (ADNI) * Patients must provide study-specific informed cons…