Clofarabine Plus Cytarabine in Patients With Previously Untreated Acute Myeloid Leukemia and High-risk Myelodysplastic Syndrome

Inclusion Criteria:

* Previously untreated acute myeloid leukemia (AML) or high-risk myelodysplastic syndrome (MDS) (\> 10% blasts). Prior therapy with hydroxyurea, single agent chemotherapy (e.g. decitabine), hematopoietic growth factors, biological or "targeted" therapies are allowed.
* Age \> 50 years to \< 74 years (diploid cytogenetics) and \< 69 years (abnormal cytogenetics).
* ECOG performance status \</= 2.
* Sign a written informed consent form.
* Adequate liver function (total bilirubin \< 2mg/dL, SGPT or SGOT \< x 4 ULN) and renal function (serum creatinine \< 2mg/dL).
* Male and female patients who are fertile agree to use an effective barrier method of birth control (ie, latex condom, diaphragm, cervical cap, etc) to avoid pregnancy. Female patients need a negative serum or urine pregnancy test within 7 days of study enrollment (applies only if patient is of childbearing potential. Non-childbearing is defined as \>= 1 year postmenopausal or surgically sterilized).
* Patients who are considered to require immediate induction (rapidly rising WBC \>/= 50,000 and/or organ involvement as per the assessment of the treating physician) can be treated without final cytogenetic results and pretreatment assessment of cardiac ejection fraction (MUGA or echocardiogram) if by history and physical examination patients have \</= NYHA class II disease.

Exclusion Criteria:

* AML with the following cytogenetic abnormalities: t(15;17), t(8;21), inv(16). Cytogenetic results do not need to be available if immediate induction is required (see inclusion #7).
* Cardiac ejection fraction \< 30%. Pretreatment assessment of ejection fraction is not necessary if immediate induction is required as long as by history and physical examination patients have \</= NYHA class II disease (see inclusion #7).
* Active and uncontrolled infection or any other severe concurrent disease considered life-threatening, or which, in the judgement of the investigator and after discussion with the Principal Investigator, would make the patient inappropriate for entry into the study.