Cyclophosphamide Followed By Busulphan in Place of Standard BuCy Regimen for Patients Undergoing Allogeneic Stem Cell Transplantation: A Preliminary Experience from a Single Centre in India

Introduction: Conditioning regimens are an important issue determining the outcome of hematopoietic stem cell transplantation (HSCT). Altering the administration order of Busulphan (Bu) and Cyclophosphamide (Cy) during conditioning from conventional method of administering Bu followed by Cy had resulted in an improved toxicity profile in few animal and subsequent human studies. However the data substantiating this approach is limited.

Methods:We retrospectively analyzed all consecutive patients receiving allogeneic stem cell transplant (Allo SCT) with myeloablative conditioning from 2009 to 2013. A total of 40 patient received Allo SCT of which 18 patient received Bu-Cy and 22 patients received Cy-Bu conditioning regimen. The Bu–Cy conditioning regimen consisted of i.v. Bu 0.8 mg/kg administered every 6 h (16 doses) on days −7 to −4, followed by i.v. Cy 60 mg/kg on days −3 and −2. Patients with the Cy–Bu regimen received i.v. Cy 60 mg/kg on days −7 and −6; followed by i.v. Bu 0.8 mg/kg administered every 6 hr (16 doses) on days −5 to −2. GVHD prophylaxis was given with Cyclosporine A and methotrexate. Common Terminology Criteria for Adverse Events version 3.0 (CTCAE) was used for assessment of toxicity. The diagnosis of sinusoidal obstruction syndrome (SOS) was based on modified Seattle criteria.

Results: Pre-transplant characteristics were comparable in the two cohorts (Table 1a and 1b). Time to platelet engraftment was earlier in the Cy-Bu cohort (21 days vs. 16 days; P=0.008) (Table 2).Treatment related side effects were similar in both the groups except hepatotoxicity (grade3-4) and nephrotoxicity (grade2-4)which was higher in Bu-Cy as compared to Cy-Bu group (10 (55.16%) vs. 3 (13.64%); p=0.03) and (8 (44.44%) vs 2 (9.09%);p=0.010) respectively. There was no significant difference in treatment related mortality (TRM) at day 100; however there was trend towards higher TRM at day 30 in Bu-Cy group (3 vs. none; p=0.083).There was no difference in aGVHD incidence, grade or stage of organ involved between the 2 groups.

Conclusion: As in previous studies hepatotoxicity in the present analysis was found to be less in patients who received Cy-Bu as the conditioning regimen and there was earlier platelet engraftment in this group. These findings suggest Cy-Bu has better toxicity profile than conventional Bu-Cy regimen. However further prospective studies are required to confirm these findings.