Allogenic Stem Cell Transplantation for Children, Adolescents and Young Adults With Relapsed or Refractory AML

1. To evaluate whether stem cell transplantation from a matched sibling donor is equivalent to a matched unrelated donor in in a second complete remission of acute myeloid leukemia (AML). 2. To evaluate whether stem cell transplantation (SCT) after chemotherapy (FLAMSA-schema) increases survival compared to a threshold derived from historical data 3. To evaluate whether SCT from haploidentical donors for children having no matched donor will result in better survival with acceptable toxicity.