315: Similar Survival after Sibling vs Unrelated Donor Allogeneic Stem Cell Transplantation with Reduced Intensity Conditioning

Abstract

Although recent studies have shown comparable survival outcomes between unrelated donor (URD) and sibling donor stem cell transplantation in the myeloablative transplant setting, little comparative data based on donor source is available in the setting of non-myeloablative/reduced intensity conditioning (RIC), where it is presumed that GvL effects must play a key role in long term survival. In this retrospective analysis, we compare the outcome of 111 patients receiving RIC followed by either matched sibling (n = 65) or unrelated donor (n = 46) peripheral blood stem cell (PBSC) transplantation for hematologic malignancies. All patients were deemed ineligible for myeloablative conditioning based on institutional standards for age, comorbid disease, and/or prior therapy. All sibling and 38 of 46 unrelated recipients received A, B, DR matched grafts. The median recipient age in both cohorts was identical; sibling 52 y (range 12–75 y) and unrelated 52 y (range 29–69 y). Conditioning regimens were primarily fludarabine/cytoxan-based in both cohorts, with URD recipients skewed toward the addition of Alemtuzumab pre-transplant (69% URD vs 25% sib), and the use of TBI 200 for 21/23 myeloma pts. The distribution of diagnoses was similar between both cohorts in patients with lymphoid malignancies (NHL, HD, CLL n = 66) 34 sib vs 32 URD, and leukemia/MDS (n = 22), 10 sib vs 12 URD; the diagnosis of myeloma (n = 23) was skewed toward sibling donors (21 vs 2 URD). Kaplan-Meier estimate of overall survival (OS) for all patients at 2 years was 31%. At a median f/u of 43 weeks in both cohorts, overall survival was nearly identical (57% sibs; 55% URD). Of note, there was no statistically significant difference in 2 year OS between sibling and URD recipients (p = 0.25), nor was there a difference in K-M estimates of OS between sibling and URD recipients when patients with lymphoid and myeloid disease were analyzed separately. Among expired patients, there was no difference in the incidence of disease-related (26/42 sibs vs 18/32 URD) or treatment-related [organ failure, infection and GvHD] (16/42 sibs vs 14/32 URD) causes of death. Furthermore, a statistically significant higher proportion of GvHD-related death among URD patients was not seen. These data support the pursuit of unrelated donors for RIC transplantation as an alternative to sibling donors without compromising overall survival.