Intensity-Modulated Radiation Therapy, Etoposide, and Cyclophosphamide Followed By Donor Stem Cell Transplant in Treating Patients With Relapsed or Refractory Acute Lymphoblastic Leukemia or Acute Myeloid Leukemia

Inclusion Criteria:

* Patients with acute lymphocytic leukemia or acute myelogenous leukemia who are not in first or second remission (i.e., after failing remission induction therapy or in relapse or beyond second remission)
* All candidates for this study must have a human leukocyte antigen (HLA) (A, B, C, DR) identical sibling who is willing to donate bone marrow or primed blood stem cells or a 10/10 allele matched unrelated donor; a single allele mismatch at A, B, C, DR, or DQ and a KIR mismatch at C will be allowed; all ABO blood group combinations of the donor/recipient are acceptable since even major ABO compatibilities can be dealt with by various techniques
* Prior therapy with VP-16, Busulfan, and Cytoxan is allowed
* A cardiac evaluation with an electrocardiogram showing no ischemic changes or abnormal rhythm and an ejection fraction of \>= 50% established by multi gated acquisition scan (MUGA) or echocardiogram
* Patients must have a serum creatinine of less than or equal to 1.2 or creatinine clearance \> 80 ml/min
* A bilirubin of less than or equal to 1.5
* Serum glutamic oxaloacetic transaminase (SGOT) less than 5 times the upper limit of normal
* Serum glutamate pyruvate transaminase (SGPT) less than 5 times the upper limit of normal
* Pulmonary functioning tests including diffusing capacity of carbon monoxide (DLCO) will be performed; forced expiratory volume in one second (FEV1) and DLCO should be greater than 50% of the predicted normal value
* The time from the end last induction or reinduction attempt should be \>= 14 days
* Signed informed consent form approved by the Institutional Review Board (IRB) is required

DONOR: Any sibling donors who are histocompatible with the prospective recipient will be considered a suitable donor

* Donors will be excluded if for psychological or medical reasons they are unable to tolerate the procedure
* Donor should be able to donate peripheral blood stem cells or bone marrow

Exclusion Criteria:

* Prior radiation therapy that would exclude the use of total-body irradiation
* Patients who have undergone bone marrow transplantation previously and who have relapsed
* Patients with psychological or medical condition that patients physician deems unacceptable to proceed to allogeneic bone marrow transplant
* Pregnancy
* Electrocardiogram (EKG) showing ischemic changes or abnormal rhythm and/or an echocardiogram or MUGA scan showing abnormal wall motion or ejection fraction \< 50%