Total Marrow and Lymphoid Irradiation and Chemotherapy for Myelodysplastic Syndrome or Acute Leukemia

Inclusion Criteria:

1. Myelodysplastic syndrome with excess blasts: Cytopenias, Unilineage or multilineage dysplasia, 5-19% blasts in bone marrow.
2. Acute lymphocytic leukemia or acute myelogenous leukemia who are in first remission or second remission.
3. Karnofsky performance status (KPS) \>= 70%
4. Women of child-bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control or abstinence) prior to study entry and for six months following duration of study participation; should a woman become pregnant or suspect that she is pregnant while participating on the trial, she should inform her treating physician immediately
5. All candidates for this study must have a human leukocyte antigen (HLA) (A, B, C, DR) identical siblings who is willing to donate 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 killer immunoglobulin-like receptor (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 (red cell exchange or plasma exchange)
6. 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
7. Patients must have a serum creatinine of less than or equal to 1.3 mg/dL or creatinine clearance \> 80 ml/min
8. Hepatic: bilirubin, aspartate aminotransferase (AST), alanine aminotransferase (ALT), Alkaline phosphatase (ALP) \< 5 x upper limit of normal (ULN)
9. Pulmonary function: Carbon Monoxide Diffusing Capacity corrected (DLCOcorr) \> 50% of normal, (oxygen saturation \[\>92%\] can be used in child where pulmonary function tests (PFT's) cannot be obtained)
10. The time from the end last induction or re-induction attempt should be greater than or equal to 14 days
11. All subjects must have the ability to understand and the willingness to sign a written informed consent

Exclusion Criteria:

1. Diagnosed extramedullary leukemia
2. Active uncontrolled infection at time of enrollment or documented fungal infection within 3 months.
3. Evidence of Human immunodeficiency virus (HIV) infection
4. Prior myeloablative transplant within the last 6 months
5. Prior radiation therapy that would exclude the use of TMLI
6. Relapsed patients who have undergone autologous or allogeneic hematopoietic stem cell transplantation previously