The aims of this study are to pilot a study to measure local control after "rational dose" selected gamma knife radiosurgery for brain metastases and to measure treatment related toxicity for rational dose selected gamma knife radiosurgery for brain metastases. In addition, the quality of life and neurocognition of patients undergoing gamma knife radiosurgery will be measured using the validated European Organisation for Research and Treatment of Cancer QLQ-C30 and QLQ-BN20 survey instruments. "Rational dose selection" is a concept wherein doses used for stereotactic radiosurgery is selected based on tumor volume, prior irradiation with whole brain radiotherapy, and the relative radioresistance of the tumor (radioresistant = melanoma, renal cell carcinoma, sarcoma; radiosensitive = breast cancer, lung cancer, colorectal cancer, gastrointestinal cancers).