Feasibility study of autologous peripheral blood stem cell transplantationfor the treatment of childhood acute myelogenous leukemia

Background: The primary object of this study was to identify treatment-rela ted variables that may predict relapse of acute myelogenous leukemia (AML) after autologous peripheral blood stem cell transplantation (PBSCT), which will be critical for the development of a suitable protocol for wider appli cation. Methods: A total of 28 children (age 0-18 years) with AML underwent PBSCT a nd have had a minimum follow-up of 25 months; including 24 patients in thei r first complete remission (CR) and four in their second CR. The patients w ere divided into two cohorts according to the study phase: 16 patients were treated in an early phase pilot study and 12 patients in their first CR we re treated in a prospective trial. Fifteen of the first-CR patients had any of the cited high-risk features of high WBC count (>100 x 10(9)/1; n = 5), FAB MO/M4/M5/M7 subtypes (n = 11) or delayed achievement of CR (n = 9). Ex cept in one patient, cytoreductive regimens did not include total body irra diation (TBI). Results: After PBSCT, one patient died of veno-occulsive disease (VOD) and another patient relapsed early on day 43, but the remaining patients showed engraftment. Leukemic relapse was observed 1-29 months after PBSCT (median , 8 months); in all of the 4 children treated in their second CR and in 11 of the 24 patients (46%) treated in their first CR. The remaining patients have been disease-free for 24 to 97 months (median, 53 months). Using a mul tivariate analysis, the timing of apheresis was the most significant progno stic factor for those treated in their first CR (p = 0.03); 12 of the 16 pa tients whose PBSC were collected beyond 2.5 months of CR continue to remain in CR, while seven of the eight patients whose PBSC were harvested within 2.5 months of CR relapsed. Conclusion: Although the small number of patients studied does not allow fi rm conclusions to be drawn regarding the relative effectiveness of this the rapy, the results do suggest the feasibility of further studies of PBSCT fo r the treatment of childhood AML with high-risk features including the asse ssment of minimum residual disease.