Definitions:
A case was defined as primary refractory, if the patient had not responded to at least one previous standard of care chemotherapy.
A case was defined as relapsed, if the patient had initially achieved a morphologic complete remission after a standard of care chemotherapy and then had experienced a relapse of the leukemia (morphologic complete remission defined as <5% leukemic cells in bone marrow). The event free survival (EFS) was defined as the time period from the first day of the first cycle of melphalan / cytarabine to the date of relapse, death or last follow-up.
The overall survival (OS) was defined as the time period from the first day of the first cycle of melphalan / cytarabine to the date of death or last follow-up. In case of death during the observation period the cause of death was subdivided into disease-related mortality and therapy-related mortality.
Treatment failure was defined as absence of complete remission without the possibility to proceed to an allogeneic hematopoietic stem cell transplantation.