Graft clonogenicity and intensity of pre-treatment: factors affecting outcome of autologous peripheral hematopoietic cell transplantation in patients with acute myeloid leukemia in first remission.

A total of 22 patients with acute myeloid leukemia (AML) in first complete remission receiving autologous blood stem cell transplantation (ABSCT) were investigated in order to determine factors affecting outcome. All but two patients had a normal karyotype and received the same high-dose chemotherapy followed by G-CSF-mobilized peripheral blood stem cells after the second (n=5) or third (n=17) course of induction and post-remission chemotherapy, respectively. With a median follow-up of 30 months, the median disease-free survival is 24.1 months. Univariate analysis showed that three chemotherapy cycles before ABSCT were associated with a significant better disease-free survival (P=0.0018) and overall survival (P=0.0033), whereas the presence of an FLT3-mutation (n=6) showed no impact. The number of megakaryocytic progenitors (CFU-MK) infused tended to correlate with primary platelet engraftment (P=0.07) and were predictive for neutrophil (P=0.011) and platelet counts (P=0.009) 180 days after transplantation. Patients receiving a higher amount of CFU-MK had a better event-free survival (P=0.02). Our data suggest that the content of CFU-MK within the graft predicts the quality of hematological recovery and long-term disease control. Additionally, a minimum of three chemotherapy cycles before ABSCT seems to be associated with an improved outcome.