Once Daily Intravenous Busulphan Plus Fludarabine As New Reduced Toxicity Myeloablative Conditioning for Acute Myeloid Leukemia and MDS Allogeneic Transplantation

Background.

Allogeneic hemopoietic stem cell transplantation is the treatment of choice for high and intermediate risk acute myeloid leukemia (AML) and for higher risk myelodysplastic syndrome (MDS). Standards preparative regimens TBI-CY and BU-CY have been widely used and extra hematologic toxicity remains a concern. Even if the combination of intravenous formulation Busulphan-CY has shown lower toxicity and suggested favorable safety and efficacy profile new drugs associations are continuously explored.

Recently the association Busulphan-Fludarabine has replaced the Bu-Cy regimen with the aim to further reduce toxicity. In our Institution we started to use this regimen as preparation for allogeneic transplantation in patients with AML and MDS in October 2008 using Busulphan in a single daily infusion with the primary objective of evaluating safety and efficacy.

Methods.

Since October 2008 to May 2014, 23 consecutive patients (19 males, 4 females) entered this study. Median age was 56 years (range 35-63). Thirteen patients presented with first remission AML, five with first or more advanced relapse or resistant disease and five with intermediate II or high risk MDS.

Conditioning consisted of intravenous Busulphan (Busilvex® 9,6 -12,8 mg/kg) given once daily in a 4 hours infusion in association with Fludarabine 160 mg /m² for 4 consecutive days.

Fifteen patients received HSCs from HLA identical siblings, 1 from a family mismatched donor, 7 from matched unrelated donors. Source of stem cells was bone marrow in 13 patients, peripheral blood stem cells in 9 patients, and both in 1 patient. CSA + short MTX was used as GVHD prophylaxis and anti-Lymphocyte globulins (Thymoglobulin® or ATG Fresenius®) was added in case of unrelated donor transplants

Toxicity was evaluated by WHO toxicity scale Common Terminology Criteria for Adverse Events (CTCAE) version 3. Acute Graft versus Host Disease was evaluated in patients with engraftment and graded according to the revised Glucksberg scale. Internal review board approved study. All patients gave written informed consent to procedure.

Results.

All patients regularly engrafted (mean time to neutrophils >500/microliter was 13 days (range 11-15).

Seven patients experienced gastro-intestinal toxicity (1 grade III mucositis, 2 grade II mucositis, 4 grade I mucositis); 3 patients had grade II cystitis. Overall grade >II toxicity occurred in a single patient (4%). Acute grade IV gastro-intestinal- GvHD occurred in 1 patient, while 12 patients presented grade I skin GvHD. Cr. GVHD occurred in 4/18 evaluable patients (moderate in 1). CMV reactivation occurred in 15/23 patients (65%), no patient developed life-threatening bacterial or fungal infection.

Eight out of 23 patients have died (35%) all but one by recurrent disease and 1 by grade IV acute GvHD. Fifteen patients are alive (65%), 14 in complete remission, with a median follow-up of 8 months (range 2-37 months).

Conclusion.

This single Centre report, even if with limited number of patients, underlines that the association of intravenous single dose infusion Busulphan plus Fludarabine is a safe and effective conditioning regimen in AML/MDS patients. Intravenous Busulphan administered once daily is convenient, well tolerated and effective. Further prospective studies are warranted.