Monoclonal Antibody Plus Chemotherapy in Treating Young Patients With Relapsed or Refractory Acute Myeloid Leukemia or Myelodysplastic Syndromes

RATIONALE: Drugs used in chemotherapy work in different ways to stop cancer cells from dividing so they stop growing or die. Monoclonal antibodies such as gemtuzumab ozogamicin can locate cancer cells and either kill them or deliver cancer-killing substances to them without harming normal cells. Combining monoclonal antibody therapy with combination chemotherapy may kill more cancer cells. PURPOSE: Phase I trial to study the effectiveness of combining gemtuzumab ozogamicin with combination chemotherapy in treating children who have relapsed or refractory acute myeloid leukemia or myelodysplastic syndrome.