Introduction Survival following allogeneic hematopoietic cell transplantation (allo-HCT) has improved over the last several decades. Implementation of reduced-intensity conditioning and improvement in graft selection, graft vs. host disease (GVHD) prophylaxis and treatment, and infection disease management, among others, have contributed to reducing non-relapse mortality (NRM). The use of post-transplant cyclophosphamide (PTCy) for GVHD prophylaxis, in particular, has been associated with reduced incidence of acute and chronic GVHD in both HLA-matched related and matched unrelated donor allografts. In this study, we aim to determine prognostic factors for NRM (including early NRM defined as within 100 days post-transplantation), disease-related mortality (DRM), and overall survival (OS) in a large cohort of patients following allo-HCT.

Methods Patients who received consecutive allo-HCT at our institution from 2009-2023 were included. Clinical data were collected from retrospective reviews of the electronic medical records. Patient- and transplant-related variables were compared between patients who died and those who were alive at 100 days post allo-HCT. Univariate and multivariate Cox proportional hazard models were used to identify prognostic associations between risk factors and OS. Kaplan-Meier method was used to evaluate OS. Log-rank test was used to compare OS between groups. Statistical significance was set to < 0.05.

Results A total of 536 patients (male=285, 53%) were included. Median age at time of allo-HCT was 59 (range, 19-75) years. Most patients were White/Caucasian (n=232, 86%). The most common diagnoses included acute myeloid leukemia (AML) (n=110, 41%), myelodysplastic syndrome (n=52, 19.2%), myelofibrosis (n=23, 9%), B-cell acute lymphoblastic leukemia (B-ALL) (n=22, 8.1%), non-Hodgkin lymphoma (n=21, 8%), and chronic myeloid leukemia (n=10, 4%). The median follow-up for survivors was 4.2 (range, 1.1-14.4) years.

A total of 80 (14.9%) patients died within 100 days with most deaths attributed to NRM (n=61, 76%). Specific causes of death included infection/sepsis in 22 (27.5%) patients, GVHD in 10 (12.5%), respiratory failure in 9 (11.2%), multiorgan failure in 5 (6.3%), graft failure in 5 (6.3%), and other causes in 10 (12.5%). Progressive disease was the cause of death in 19 (23.8%) patients.

Male gender (HR=1.92; p= 0.006), remission status other than CR1 or CR2 for acute leukemia patients (HR=8.44; p<0.0001), non- PTCy strategies (HR=2.4; p= 0.0006), and earlier year of transplantation (HR=1.12; p=< 0.001) were associated with increased risk of mortality at 100 days on univariate analysis. Only use of TBI (HR=2.56, p=0.048) and earlier year of transplantation (HR=1.2; p=0.001) were associated with increased risk of DRM at 100 days post-allografting on univariate analysis. Pertaining to risk of NRM at 100 days, male gender (HR=1.89; p=0.02), diagnosis other than acute leukemia (HR=2.27; p=0.004), non-PTCy strategies (HR=2.44; p=0.003), and earlier year of transplantation (HR=1.1; p=0.004) were adversely associated with NRM. On multivariate analysis, only earlier year of transplantation was found to be associated with increased risk of DRM at 100 days (HR 1.15; p=0.049). Male gender (HR=1.78; p=0.035), diagnosis other than acute leukemia (HR=2.38; p=0.003), and non-PTCy strategies (HR=2.2; p=0.032), were associated with increased risk of NRM at 100 days.

Conclusion Non-relapse mortality (NRM) accounted for most deaths within the first 100 days of allo-HCT, primarily due to infection/sepsis and GVHD. Factors associated with increased NRM included male gender and diagnoses other than acute leukemia. Significantly, post-transplantation cyclophosphamide (PTCy) was the only treatment strategy modification that decreased 100-day NRM and improved survival, independent of the transplantation year.

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2025
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