Allogeneic Hematopoietic Stem Cell Transplantation for Elderly Acute Lymphoblastic Leukemia Patients: A Registry Study from the Société Francophone De Greffe De Moelle Et Thérapie Cellulaire (SFGM-TC)
Authors: Chalandon Yves , Devillier Raynier , Boumendil Ariane , Nguyen Quoc Stéphanie , Bulabois Claude-Eric , Ceballos Patrice , Brissot Eolia , Rubio Marie Thérèse , Labussière-Wallet Hélène , Maertens Johan , Chevallier Patrice , Maillard Natacha , Poiré Xavier , Castilla-Llorente Cristina , Beguin Prof. Yves , Cornillon Jérôme , Maury Sebastien , Marchand Tony , Daguindau Etienne , Bay Jacques-Olivier , Turlure Pascal , Charbonnier Amandine , Menard Anne , Bilger Karin , Guillerm Gaelle , François Sylvie , Bazarbachi Ali , Chantepie Sylvain , Lewalle Philippe , Marcais Ambroise , Loschi Michael , Benakli Malek , Chauvet Paul , Forcade Edouard , Huynh Anne , Robin Marie , Masouridi-Levrat Stavroula 
Published: December 2023

Background
There are very scarce data regarding the outcome of elderly patients with acute lymphoblastic leukemia (ALL) who received allogeneic hematopoietic stem cell transplantation (alloHSCT) as consolidation therapy in 1rst or higher complete remission (CR). Most studies evaluating the benefit of alloHSCT in ALL include both young and elderly populations. Thus, the optimal conditioning regimen still need to be determined in a frail population represented by patients over 60 years old. In addition, total body irradiation (TBI) dose is of first importance, as prior reports demonstrated its potential higher anti-leukemic effect. We here present the outcome of ALL patients older than 59 years from the Société Francophone de Greffe de Moelle et Thérapie Cellulaire (SFGM-TC) registry.
Method
This is a retrospective study. The primary outcome was overall survival (OS). Secondary outcomes were progression free survival (PFS), non-relapse mortality (NRM), relapse incidence (RI), acute Graft-versus-host disease (aGvHD) grade II-IV, chronic GvHD, neutrophil engraftment and GvHD-free relapse-free survival (GRFS). Competing risks analyses were performed to analyze NRM with competing event relapse, and aGvHD grade II-IV, chronic GvHD and neutrophil engraftment with competing events relapse and death. Univariable analyses were performed using the log-rang test for OS and PFS, while Gray's test was used for cumulative incidence (CI). Multivariable analyses were performed using the Cox proportional hazards regression model including age, ALL subtype, time from diagnosis to alloHSCT, disease status at alloHSCT, donor to patient CMV status, donor to patient sex, ATG use, myeloablative conditioning (MAC), TBI use.
Results
A total of 316 patients ≥ 60 years old transplanted for ALL from 2012 to 2022 in 36 participating centers were included in this study. Patient's characteristics are described in Table 1. With a median follow up of 34.5 months (IQR 29.5-38.8), 3-year OS was 46% (95% CI 40-53%) (Figure 1A) with only the disease status at transplant impacting negatively OS, 53% (95% CI 46-60%) in CR1, 32% (95% CI 21-49%) in CR2, 29% (95% CI 13-63%) in advanced disease, p=0.002 and the ALL subtype, 59% (95% CI 51-68%) in Ph+ ALL, 40% (95% CI 29-54%) in Ph- ALL, 34% (95% CI 20-55%) in T-ALL, 20% (95% CI 9-42%) in other/NA, p&lt;0.001. 3-year PFS was 41% (95% CI 35-48%) (Figure 1B) with the disease status at transplant impacting negatively, 49% (95% CI 42-57%) in CR1, 26% (95% CI 16-42%) in CR2, 22% (95% CI 9-58%) in advanced disease, p&lt;0.001, the ALL subtype, 51% (95% CI 42-61%) in Ph+ ALL, 41% (95% CI 31-54%) in Ph- ALL, 21% (95% CI 10-41%) in T-ALL, 21% (95% CI11-43%) in other/NA, p&lt;0.001, year of HSCT worse &lt; 2018, p=0.007, CMV -/- worse, p=0.033, absence of TBI worse, p=0.018. 3-year NRM was 23% (95% CI 18-28%) (Figure 1C) and none of the factors impacted it. 3-year RI was 36% (95% CI 31-42%) (Figure 1D) with the disease status at transplant impacting negatively, 29% (95% CI 23-36%) in CR1, 50% (95% CI 35-63%) in CR2, 56% (95% CI 26-77%) in advanced disease, p=0.0042, the ALL subtype, 26% (95% CI 19-34%) in Ph+ ALL, 43% (95% CI 31-54%) in Ph- ALL, 57% (95% CI 38-73%) in T-ALL, 42% (95% CI 25-59%) in other/NA, p=0.0064, year of HSCT worse &lt; 2018, p=0.0216, CMV -/- worse, p&lt;0.001, absence of TBI worse, p=0.0069, MRD worse, p=0.0111. 3-year GRFS was 30% (95% CI 25-37%) with the disease status at transplant impacting negatively, 35% (95% CI 28-43%) in CR1, 22% (95% CI 13-37%) in CR2, 23% (95% CI 9-59%) in advanced disease, p=0.029, the ALL subtype, 37% (95% CI 30-47%) in Ph+ ALL, 33% (95% CI 23-46%) in Ph- ALL, 15% (95% CI 7-32%) in T-ALL, 17% (95% CI 8-38%) in other/NA, p=0.0029, year of HSCT worse &lt; 2018, p&lt;0.001. CI of aGVHD grade II-IV was 33% (95% CI 28-38%), grade III-IV 11% (95% CI 8-15%), cGVHD 35% (95% CI30-41%), extensive cGVHD 21% (95% CI 16-26%).Multivariable analyses confirmed a worse OS and PFS for advanced disease, with a HR of 1.79 (95% CI 1.22-2.64), p=0.00322 and ALL subtype with a HR for other than Ph+ ALL of 1.99 (95%CI 1.42-2.79).
Conclusion:
This study suggests that alloHSCT is a reasonable option for elderly ALL patients without any impact of age but advanced disease and ALL subtype other than Ph+ ALL negatively influenced the outcome.