Allogeneic stem cell transplantation after conditioning with treosulfan, etoposide and cyclophosphamide for patients with ALL: a phase II-study on behalf of the German Cooperative Transplant Study Group and ALL Study Group (GMALL).

TBI-based preparative regimens are considered as standard conditioning therapy for allogeneic stem cell transplantation (AHSC) in patients with ALL. We investigated toxicity and efficacy of a non-TBI-based regimen consisting of treosulfan, etoposide and cyclophosphamide for ALL within a prospective study. Major inclusion criteria were CR and non-eligibility for TBI. Fifty patients with a median age of 46.5 years (range, 18-64) were included. Donors were HLA-identical sibling (n=8), matched (n=42) or mismatched (n=10) unrelated. The toxicity was moderate, resulting in a cumulative incidence of non-relapse mortality (NRM) at 1 year of 8% (90% confidence interval: 2-15%). Acute GvHD grade II-IV and grade III/IV was noted in 53% and 14%, respectively. Chronic GvHD at one year was seen in 41%. After a median follow-up of 24 months the cumulative incidence of relapse was 36% (90% confidence interval: 24-48) and 51% (90% confidence interval: 37-65) at 1 and 2 years, respectively. The estimated 2-year disease-free and overall survivals were 36 and 48%, respectively. Treosulfan, etoposide and cyclophosphamide followed by AHSC has a favorable toxicity profile with low NRM and therefore represents a potential alternative regimen for ALL in 1. CR (NCT00682305).