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.
Age ≥18 years at diagnosis of brain metastases.
Eastern Cooperative Oncology Group (ECOG) Performance Score of <2.
Participants must have a biopsy-proven solid malignancy (histologic proof or unequivocal cytologic proof solid tumor malignancy from either the primary or any metastatic site) with intracranial lesions radiographically consistent with or pathologically proven to be brain metastases.
Patients who have undergone prior systemic therapy are eligible.
Metastases from hematological malignancy, or central nervous system malignancy.
Patients whose malignancy is being treated with curative intent.
Leptomeningeal metastases.
Contraindication to MRI imaging with contrast.
Single group
Memantine -Twice Daily or Extended Release
DrugBoth extended release memantine and twice daily memantine dosing will be allowed. Twice daily dosing: The target dose for memantine is 20 mg (10 mg divided twice daily). Dose will be escalated by 5 mg each week to a target of 10 mg twice daily (i.e., 5 mg a day on week 1, then 5 mg twice daily (BID) on week 2, then 10 mg in AM plus 5 mg in PM on week 3, followed by 10 mg in AM plus 10 mg in PM by week 4). Extended Release Memantine: The target dose for extended release memantine is 28 mg. Dose will be escalated by 7 mg per week to a target of 28 mg daily (i.e., 7 mg a day on week 1, then 14 mg a day on week 2, then 21 mg a day on week 3, followed by 28 mg a day by week 4).
WBRT utilizing the PRDR technique
RadiationThe total dose of 3000 cGy (30 Gy) will be divided 10 fractions of 300 cGy (3 Gy); each fraction will be delivered as a series of 20 cGy (0.2Gy) pulses separated by 3 min time intervals. 20 cGy / 3 min = 6.67 cGy/min (or 0.0667 Gy/min). Total time is determined by the fractionated series and time intervals, meaning 300cGy/20cGy = 15 division x 3 minutes = 45 minutes. Including time to set up, approximate total time per treatment session will be 60 minutes.
Successful completion of PRDR WBRT treatment
The number of subjects successfully completing PRDR WBRT treatment within five days of intended treatment completion.
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