Some cancers can spread, or metastasize, to the brain. When they do, treatment often involves surgery and/or radiation. Optimal treatment of brain metastases would maximize disease control and minimize toxicity (or side effects), and improve the quality of life of patients. A common type of radiation used for brain metastases is called whole brain radiation, which treats not just the cancer that can be seen on scans (i.e., gross disease), but the smaller sites of cancer that may not be visible (i.e. subclinical disease). Fractionation is used to describe repetitive treatments in which small doses (fractions) of a total planned dose are given at separate clinic visits. The most common dosing regimen is 30 Gray (Gy), using 3 Gy per fraction over 10 fractions. Previous studies have suggested that using intensity modulated radiation therapy (IMRT) may be a safer way to deliver higher doses to gross disease and lower doses to the rest of the brain that may contain subclinical disease. This approach may spare the rest of the brain from radiation complications and side effects.