Patients with >=4 brain metastases will undergo Gamma Knife radiosurgery to a dose of 15-20 Gy, depending on the maximum tumour diameter and number of metastases. A number of neurocognitive, quality of life, and toxicity assessments will be performed at baseline and at 6 weeks post-radiosurgery, then at months 4, 6, 12, 18, and every 6 months thereafter.