Allogeneic Stem Cell Transplantation Using In Vivo T-Cell Depletion in Myeloid Disorders

Introduction:

Alemtuzumab is used for in vivo T-cell depletion to reduce graft versus host disease in allogeneic Stem Cell Transplantation (SCT). Profound lymhotoxicity of this monocloncal antibody can potentially increase morbidity and mortality in SCT due to excessive viral infections and increased risk of graft rejection. We retrospectively analysed outcome of patients with myeloid disorders (acute myeloid leukaemia and myelodysplasia) who received in vivo T-cell depletion using Alemtuzumab based conditioning for allogeneic SCT over a period of 3 years in our centre.

Methods:

Patients were identified from department transplant data base. Data was collected for 73 consecutive patients over a period of three years using patient medical records, clinical work station and electronic patient records. The conditioning regimen included Fludarabine 30mg/m2 x5 (days -7 to -3), Alemtuzumab 10mgx5 (days -8 to -4) and Melphalan 140mg/m2 (day -2). Chimerism analysis was performed by polymerase chain reaction (PCR) to identify short tandem repeats within peripheral blood leucocytes and CD3 fraction. The quantification of donor chimerism was done by using gel photography system and LabWroks software. Viral testing was performed by PCR analysis.

Results:

Median age for the patients was 59 years (range 41-71). Median duration of follow up was 19 months (4-49 months). The majority of patients (67%) received SCT from a voluntary unrelated donor. Sixty four patients (88%) had AML whilst 9 had myelodysplasia. Sixty five (89%) patients were in morphological complete remission (<5% blasts) at the time of SCT. Median HCT-Comorbidity index was 2 (range 1-5). Median time to neutrophil engraftment was 13 days (range 9-23) and platelet engraftment 14 days (median 8-48). During the course of transplantation, 50 patients were treated for neutropenic fever with broad spectrum antibiotics and 16 for presumed fungal infection. Forty three patients (59%) reactivated cytomegalovirus (CMV), 10 (13%) had Ebstein Barr Virus (EBV) viremia and 4 (5%) were found to have adenovirus on peripheral blood PCR analysis after SCT. Denovo acute graft versus host disease (grade 2-4) required treatment in 12 patients (16%) whilst chronic GVHD was seen in 14% (n=10). 20 patients required donor lymphocyte infusion due to mixed chimerism after SCT. Total incidence of acute GVHD (grade 2-4) was 23% (n=17) and that of chronic GVHD was 15%. Median donor chimerism in peripheral blood leucocyte fraction was 100% at day 30, 60, 90 and 180 after SCT. Chimerism analysis on CD3 compartment showed 100%, 96%, 95.5% and 95% donor fraction respectively at these time points. Predicted overall survival at 2 years was 53% and Event Free Survival 49%. Non relapsed mortality in this cohort was 18% at one year. One patient had primary graft rejection with no secondary graft rejections. Overall survival was not statistically different between those who were treated for viremia (CMV, EBV, adenovirus) when compared to those who did not have viremia (p=0.31). No deaths were attributed to either CMV or EBV.

Conclusion:

Our retrospective data show that Alemtuzumab based conditioning regimen in myeloid disorders have low incidence of GVHD, very low risk of graft rejection and comparable overall survival to those conditioning regimens which utilize in vivo T-cell depletion strategies other than Alemtuzumab. Moreover, a high incidence of viremia, in our cohort, did not translate into worse overall survival.