Status of Minimal Residual Disease Determines Outcome of Autologous HSCT in Adults with High-Risk Acute Lymphoblastic Leukemia.

Abstract 2321

Poster Board II-298

The role of autologous hematopoietic stem cell transplantation (autoHSCT) in the treatment of adult acute lymphoblastic leukemia (ALL) is a subject of controversies as several prospective studies failed to prove its advantage over maintenance chemotherapy. Those studies, however, did not take into account the status of minimal residual disease (MRD), which is now recognized a potent predictor for relapse among patients treated with conventional-dose chemotherapy. The goal of this analysis was to determine the impact of MRD on outcome of autoHSCT.

Data on 123 autoHSCT recipients collected from 6 study groups cooperating in the European Leukemia Net were analyzed. Median age of 77 B-lineage and 46 T-lineage high-risk ALL patients was 31 (16-59) years. Ph+ ALL was recognized in 20 cases. All patients were in first complete remission (CR) lasting 6 (1.5-22) months. Peripheral blood was used as a source of stem cells in 67 patients whereas bone marrow, in 56 cases. Conditioning was based on chemotherapy alone (n=76) or total body irradiation (n=47). MRD was evaluated in bone marrow with the use of either multiparametric flow cytometry (n=79) or molecular techniques (n=44). MRD level of 0.1% bone marrow cells was used as a cut-off point for the purpose of this study. At the time of autoHSCT MRD was &0.1% in 93 patients and ≧0.1% in 30 cases.

With the median follow up of 5 years, the probability of leukemia-free survival (LFS) at 5 years for the whole group equaled 48% (+/-5). Three patients died of transplantation-related complications. The LFS rate was significantly higher for patients with the MRD level at transplantation &0.1% compared to those with MRD ≧0.1% (57% vs. 19%, p=0.0002). The difference was particularly pronounced for peripheral blood HSCT (66% vs. 20%, p=0.0006) and for T-lineage ALL (62% vs. 8%, p=0.001). In a multivariate analysis adjusted for other potential prognostic factors (age, CR duration, Ph+ ALL, immunophenotype, source of stem cells, type of conditioning), the MRD status &0.1% remained the only independent factor associated with increased LFS (HR=2.5, p=0.0009).

CONCLUSIONS: MRD status is the most important predictor for LFS after autoHSCT in adults with ALL. More than half of patients with high risk disease and low MRD level at the time of transplantation may be cured. This observation may contribute to re-evaluation of the role of autoHSCT in the therapy of adult ALL.