Toxicological effects of fludarabine and treosulfan conditioning before allogeneic stem-cell transplantation

We studied early potential treosulfan-related toxicity in 118 patients treated with treosulfan-based conditioning before allogeneic hematopoietic stem-cell transplantation. Most patients (n = 93) had a hematological malignancy. In 80 cases, a HLA-A, -B and -DR matched unrelated donor was used, while 33 patients had a HLA-identical sibling donor, and five received an HLA-A, -B or -DR allele mismatched, unrelated donor. Levels of AST, ALT, and bilirubin were significantly increased 1 week after HSCT compared to before HSCT. However, only a few patients had transaminase levels >2 to 3 × the upper normal level. All patients became neutropenic; 61% were already so at the time of graft infusion. Nearly all patients engrafted, except for three who died very early. Non-relapse mortality was 7.5% at 100 days and 11.9% at 1 year after HSCT. Veno-occlusive disease of the liver occurred in one patient and hemorrhagic cystitis in two patients. This study shows that early regimen-related toxicity after HSCT was low despite similar marrow toxicities compared to myeloablative regimens.