Hippocampal-sparing Whole Brain Radiotherapy for Brain Metastases From Breast Cancer

Inclusion Criteria: * Female patients with advanced breast cancer who is confirmed historically. * New developing brain metastases (BM) is confirmed by gadolinium contrast-enhanced magnetic resonance imaging (MRI), with or without clinical symptoms and pathology, and without a history of BM treatment. * At least 2 BM lesions with the diameter of the largest lesion \< 40 mm is eligible. And the distance from the border of a mass to the hippocampal margin should be more than 15 mm. * The Eastern Cooperative Oncology Group (ECOG) is from 0 to 2, and the expected life expectancy is ≥3 months. Exclusion Criteria: * Concurrent chemoradiation. * Patient who had received cranial irradiation previously. * Patient who are enrolled in other clinical trial at the same time. * Patient who has severe co-morbidity or infection.