No Difference in Relapse Free Survival When Comparing Reduced Intensity Conditioning Regimens in Transplant for Myeloid Malignancies

Introduction Hematopoietic cell transplantation (HCT) remains a curative therapy for many patients with myeloid disorders. Conditioning regimens to reduce disease burden and decrease the risk of graft rejection are implemented prior to HCT through the form of conditioning regimens. While many of these regimens are available, there is no consensus and regimens are oftentimes institution-dependent [1]. We present a retrospective analysis of several reduced intensity conditioning (RIC) regimens. Methods This was a retrospective study with an aim of comparing survival outcomes in patients with myeloid disorders [acute myeloid leukemia (AML), chronic myeloid leukemia (CML), myelodysplastic disorders (MDS), and myeloproliferative neoplasms (MPN)] who underwent HCT at our institution between the years 2008-2017. RIC regimens included carmustine + fludarabine + melphalan (BCNU/Flu/Mel), fludarabine + melphalan (Flu/Mel), and busulfan + fludarabine (RIC Bu/Flu). Baseline disease and patient-related characteristics were obtained by systematic review of the electronic medical record. Overall survival and relapse-free survival were estimated according to the Kaplan Meier method. Cox proportional hazards regression models were estimated with conditioning regimen and ASBMT risk levels as predictors of relapse-free survival. Linear Model ANOVA and Pearson's Chi-squared test were utilized to examine differences in patient characteristics by regimen group. Results There were 154 patients included. Of these, 120 (44.4%) were women, and the median patient age at transplant was 64 years. Patients were diagnosed with AML (48.7%), MDS/MPN (42.9%), CML (1.3%) or other variants (7.1%). A majority of patients (81.2%) received matched unrelated donor (MUD) transplants with others receiving allogenic (18.8%) transplants. Most patients were classified as low risk (49.3%), 40.8% were classified as high risk, and 9.9% were classified as intermediate risk using ASBMT guidelines. Median length of follow-up post treatment across all patients was 651 days. The three year rate of relapse-free survival was 74% (95% CI 0.64-0.84) for patients who received a RIC. Statistically significant differences by regimen group at p