Outcomes for Allogeneic Hematopoietic Cell Transplantation for AML and High-Grade MDS in Older Adults in the Era of T-Replete Haploidentical Donor Grafts. a Single Center Multivariate Analysis
Authors: Bashey Zain , Solomon Scott R. , Morris Lawrence E. , Holland H. Kent , Zhang Xu , Solh Melhem 
Published: October 2019

Abstract
Introduction: Outcomes for non-transplant therapy in older adults (age> 60 years) with AML or high-grade MDS have historically been poor. Allogeneic hematopoietic cell transplantation (allo-HCT) may improve these outcomes. However, many older patients will lack suitably HLA-matched sibling donors (MRD). Furthermore, many patients from ethnic minorities will lack an optimally matched unrelated donors (MUD). Additionally, the greater incidence and severity of chronic GVHD typically seen following MUD transplants may be particularly difficult to tolerate in older patients. T-replete haploidentical donor transplants (HAPLO) using post-transplant cyclophosphamide to mitigate alloreactivity may provide a suitable donor option for some older patients. However, no detailed comparison of outcomes after HAPLO to MRD and MUD donors in elderly patients with AML and high-grade MDS have been reported in the modern era..
Methods: We analyzed outcomes of patients aged > 60 years with AML or high-grade MDS who received an allo-HCT at our center between 2005 and 2015. Ex-vivo T-cell depleted transplants and cord blood transplants were excluded. Supportive care measures were identical between the three donor groups. Patient characteristics and outcome parameters were extracted from our institutional database where they had been prospectively entered. Kaplan-Meier estimates of overall survival (OS) and disease-free survival (DFS) were calculated and the cumulative incidence method with competing risks was used to calculate rates of non-relapse mortality (NRM) and relapse. Cumulative incidences of acute and chronic GVHD were estimated with death being treated as the competing risk. Cox proportional hazards models, stratified on the three transplant donor groups, were developed using OS, DFS, NRM and relapse as endpoints and other parameters as covariates. GVHD was prospectively documented by a single dedicated nurse using established criteria including NIH consensus criteria for chronic GVHD and rates calculated using the cumulative incidence method.
Results: Patient characteristics (n=127, 33 HAPLO, 37 MRD, 57 MUD) were as follows: median age 64 (60-77); male 57%; regimen- myeloablative (24%) non-myeloablative (76%); graft- PBSC (80%) BM (20%); Diagnoses- AML 59%, MDS 41%; DRI- low (2%), intermediate (58%), high (39%), very high (1%); Sorror HCT-comorbidity index 0-2 (46%), >3 (54%); Median HLA mismatches were 5/10 (range 2/10 to 5/10) for HAPLO patients. Estimated rates of OS, DFS, NRM and relapse for the entire group at 2 years were 60%, 49%, 18%, and 33%. When compared to MRD and MUD, HAPLO patients had similar characteristics but were less likely to have myeloablative conditioning (6% vs. 32% and 30% respectively for MRD and MUD, p=0.016) and were more likely to have a BM graft (52% vs. 0% and 21%, p<0.001). Median follow-up of surviving patients following MRD, MUDT and HAPLO transplants were 34m, 26m and 17m. For MRD, MUD, and HAPLO transplants respectively, estimated outcomes are as follows: TRM at 1year: 14%, 14% and 9% and 2yrs 17%, 23%, 9%, Relapse at 1year - 25%, 34%, 22% and 2 yrs -32%, 34%, 33%; OS at 1 yr 72%, 72%, 77% and 2 yrs - 62%, 55% , 67%. DFS at 1 yr - 61%, 52%, 69% and 2 yrs - 51%, 43%, 58% (Fig 1.) (p=NS for all endpoints on pointwise and global comparison). The cumulative incidences of acute GVHD at 180 days were: grade 2-4 - 27%, 37% and 39%; grade 3-4 - 8%, 18% and 15% (p=NS for all) and chronic GVHD at 2 yrs were: moderate to severe - 38%, 35%, 15% (p=0.028 MUD vs HAPLO, p=0.026 MRD vs HAPLO); severe - 12%, 11%, 0% (p=0.030 MUD vs HAPLO, p=0.009 MRD vs HAPLO). On multivariable Cox analysis, donor type was not a significant predictor of OS, DFS, NRM or relapse (Table 1).
Conclusions: The results show that in the current era, using predominantly non-myeloablative conditioning regimens, 2 year OS and DFS rates of 60% and 49% with a NRM <20% can be achieved in patients aged >60 years who undergo allo-HCT for AML and high-grade MDS. Outcomes of patients transplanted from HAPLO donors are comparable to those from matched donors although the rate of clinically significant chronic GVHD appears significantly less following HAPLO transplants, which may translate to an improved quality of life.
Figure 1 Figure 1. Figure 2 Figure 2. Table 1 Multivariate Analysis on Overall Survival, Disease Free Survival, Transplant Related Mortality and Relapse Table 1. Multivariate Analysis on Overall Survival, Disease Free Survival, Transplant Related Mortality and Relapse

Disclosures
No relevant conflicts of interest to declare.