The goal of this clinical research study is to learn if your thinking ability (cognitive function) will be better preserved by delivering whole brain radiation therapy immediately after radiosurgical treatment of 1-3 brain metastases or to carefully observe patients after radiosurgery and hold back whole brain radiation therapy until the disease comes back.

Before treatment starts, patients will have a complete history (including details of previous chemotherapy, radiotherapy, and surgery for systemic disease). Patients will have a complete neuropsychological exam and will have their Karnofsky Performance Score (KPS) figured out. Seven cognitive function tests and a quality of life (QOL) questionnaire will be given to the patients as well. It will take about 40 minutes to complete the QOL questionnaire.

Patients in this study will be randomly picked (as in the toss of a coin) to be in one of two treatment groups. Patients in one group will receive immediate whole brain radiation therapy. Patients in the other group will hold off on radiation and just be closely observed. There is an equal chance of being in either group.

All patients will receive radiosurgery treatment to the known metastases (1-3 lesions) at the beginning. All participants will be followed with serial diagnostic and functional MRI. Experimental functional imaging will be used to evaluate short-term memory and picture recognition as well as blood flow within the brain.

Formal neuropsychological testing will also be performed at each follow-up interval. Patients must come back at 4 months for neuropsychological testing. Patients will be seen for follow-up with neuropsychological evaluation, as well as diagnostic/function MRI at 1 , 2 , 4 , 6 , 9 , 12 , 15 , and 18 months and then every six months from then on. Each visit will require about 40 minutes of time.

Cost information related to protocol treatment and subsequent therapies will be tracked and collected for cost analysis between the two treatment groups.

Patients who did not receive whole brain radiation and develop recurrent disease shall receive treatment based on the number of lesions. If there are greater than 2 lesions, whole brain radiation will be given. If there are 1-2 lesions, patients will be randomly assigned to a local treatment (surgery or radiosurgery) or whole brain radiation therapy. Further recurrences in patients having not yet received whole brain radiation will be given this treatment at the time of recurrence.

The expected length of the study is 3.8 years with 6 months follow-up following the end of the study. Thus, the length of participation can range from 6 months for patients enrolling at the end of the study to over 4 years for patients enrolling at the beginning.

This is an investigational study. A total of 152 patients will take part in the study. All will be enrolled at MD Anderson.

Inclusion Criteria:

1)age 18 and older at time of registration. 2) recursive partitioning class (RPA) I or II. 3) 1 to 3 newly diagnosed brain metastases 4) must be eligible to have all lesions treated by SRS as determined by the radiation oncologist on the basis of location and size. 5)MRI with contrast must be performed with 1 month of registration. 6)Signed informed consent form approved by the IRB agreeing to randomization .

Exclusion Criteria:

1) prior WBRT 2) prior resection of brain metastasis, SRS or Gamma knife. 3) > 3 brain metastases present on MRI 4) lymphoma, small cell lung cancer, leukemia, germ cell tumors. 5) leptomeningeal disease. 6) unknown primary.7) RPA Class III (i.e. KPS < 70) 8) pregnancy.

Post-entry exclusion: No post-entry exclusions will be allowed after registration has occurred. All randomized patients will be included in the analysis and those lost to follow-up will be assigned the least favorable outcome (recurrence, death).