Based on evidence that radiation-induced damage to the hippocampus plays a considerable role in neurocognitive decline after cranial irradiation, hippocampal-sparing whole brain radiation therapy (HS-WBRT) has been proposed. This study will investigate the neurocognitive function and prognosis between HS-WBRT and conventional WBRT for the treatment of 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.