Predictive Factors and Outcomes after Allogeneic Stem-Cell Transplantation for Adults with Acute Lymphoblastic Leukemia in Brazil
Authors: Silva Wellington F , Cysne Dalila , Kerbauy Mariana Nassif , Colturato Iago , Maia Ana Carolina Arrais , Tucunduva Luciana , Barros George , Colturato Vergilio Rensi , Hamerschlak Nelson , Rocha Vanderson 
Published: November 2021

Abstract
Introduction: Allogeneic stem-cell transplantation (HSCT) remains a potentially curative approach for acute lymphoblastic leukemia (ALL), especially for high-risk patients and those with relapsed/refractory disease, although its efficacy is offset by a not negligible toxicity. Adult patients with ALL fare worse in developing countries with low data about the HSCT in this setting. In this study, we aim to describe outcomes and examine risk factors for overall survival (OS), disease-free survival (DFS), cumulative incidence of relapse (CIR), non-relapse mortality (NRM) and graft-versus-host disease (GVHD) after HSCT for ALL in Brazilian centers.
Methods: This is a retrospective registry study. Patients with ALL or ambiguous lineage leukemia above 16 years who underwent a first HSCT in 5 Brazilian centers between January 2007 and December 2017 were included. Kaplan-Meier method and competing risk analysis were used. Multivariable analysis (MVA) was performed using Cox regression and the Akaike's information criteria was used for model selection. Cut-offs for continuous variables were calculated through "findcut" R function. Center effect was evaluated by using frailty model.
Results: Overall, 275 patients were included with a median age of 31y (range, 16-65). Philadelphia chromosome was found in 35%. Baseline characteristics are summarized in Table 1. Matched sibling donor (MSD), matched unrelated donor (MUD), mismatched unrelated donor (MMUD), haploidentical donor and umbilical cord were reported in 53%, 19%, 9%, 19%, and 5%, respectively. Total body irradiation (TBI) was used in 67% of myeloablative HSCT. Median time to HSCT in CR1 was 7.8 months. Engraftment failure rate was 1.5%. Median follow-up time was 6.4 y. Cumulative incidence of acute grade II-IV and chronic GVHD were 54.2% and 26.2%, respectively. In MVA, the use of MUD (HR=2.3) and increased donor age (HR=1.02) were associated with GVHD. Five-year CIR was 28.1% (95% CI 22.9-33.6) and 5-y NRM was 34.1% (95% CI 28.4-39.8). At D+100, NRM incidence was 22.6%. Central nervous system involvement at the diagnosis (HR=2.2), and disease status (HR 1.8 for CR2+, and HR 7.9 for refractory) increased relapse incidence, whereas the use of peripheral blood graft (HR=0.51) and haploidentical donor (HR=0.4) significantly decreased relapse incidence. In MVA, NRM was increased by patient's age (HR=1.04), refractory status (HR=4.2), MUD (HR=3.8) and donor age (HR=1.02). Center effect was significantly associated with relapse and NRM. Five-year OS and DFS were 40.7% (95% CI 35.1-47.1) and 37.8% (95% CI-32.3-44.1), respectively (Figure 1). Patient's age, donor age and disease status were independently associated with OS and DFS (Table 2). When GVHD (as a time-dependent variable) was introduced in the MVA for OS and DFS, it was associated with decreased OS (HR 4.2, p&lt;0.001) but not with DFS. Pre-HSCT positivity of minimal residual disease (&gt;0.01%) was associated with worse DFS in univariate analysis (HR=1.47) in available cases.
Conclusions: This is the largest series of ALL adults receiving HSCT from Brazil. While OS and DFS were similar to published data, NRM was higher. Patient's age and donor age outweighed donor type or graft source in our analysis. Interestingly, haploidentical HSCT related to lower CIR, whereas the use of MUD was associated with higher NRM and GVHD rates. These results impact on donor selection strategy in our country, aiming to timely offer HSCT for high-risk ALL patients in our setting.
Figure 1 Figure 1.

Disclosures
No relevant conflicts of interest to declare.