Cytarabine Alternating with Decitabine

The goal of this clinical research study is to learn if cladribine given in combination with low-dose cytarabine (LDAC) and decitabine can help control the disease in patients with AML or MDS. The safety of this drug combination will also be studied. Cladribine is designed to interfere with the cell's ability to process DNA (the genetic material of cells). It can also insert itself into the DNA of cancer cells to stop them from growing and repairing themselves. Cytarabine is designed to insert itself into DNA of cancer cells to stop them from growing and repairing themselves. Decitabine is designed to damage the DNA of cells, which may cause cancer cells to die. This is an investigational study. Cladribine is FDA approved and commercially available for use in patients with hairy cell leukemia. Its use in patients with AML is investigational. Cytarabine is FDA approved and commercially available for use in patients with AML. Decitabine is FDA approved and commercially available for use in patients with MDS. Its use for patients with AML is investigational. Up to 160 patients will take part in this study. All will be enrolled at MD Anderson.