Autologous stem cell transplantation for adults with Philadelphia-negative acute lymphoblastic leukemia in first complete remission. A study by the Acute Leukemia Working Party of the EBMT

Background: The role of autologous hematopoietic stem cell transplantation (AHSCT) in adults with Philadelphia chromosome-negative acute lymphoblastic leukemia (Ph-ALL) remains controversial. The aim of this retrospective study was to analyze results of AHSCT and to identify prognostic factors. Methods: Overall, 700 patients transplanted in first complete remission between the years 1999-2020 were included. Median patient age was 31.9 years (68% male). B-cell precursor ALL (BCP-ALL) and T-cell precursor ALL (TCP-ALL) was diagnosed in 35% and 65%, respectively. Among 190 patients with available data, negative minimal residual disease (MRD) status was reported in 167 (88%) cases. Results: The probabilities of overall survival (OS) and leukemia-free survival (LFS) at 2 years were 67% and 56%; relapse incidence (RI) and non-relapse mortality (NRM) were 39% and 5%, respectively. TCP-ALL was associated with lower RI (41% vs. 56%, p=0.001), higher LFS (52% vs. 38%, p=0.002) and OS (58% vs 45%, p=0.001) at 5 years when compared to BCP-ALL. In the multivariate analysis, TCP-ALL and longer interval from diagnosis do AHSCT were associated with reduced risk of relapse (HR 0.7, p=0.006 and HR=0.95, p=0.018), better LFS (HR=0.76, p=0.02 and HR=0.95, p=0.01) and OS (HR=0.75, p=0.024 and HR=0.94, p=0.013, respectively). Increasing patient age was associated with higher NRM (HR=1.49, p<0.0001), worse LFS (HR=1.1, p=0.01) and OS (HR=1.17, p=0.0001). Conclusions: Autologous hematopoietic stem cell transplantation is relatively safe option of late treatment intensification in adults with Ph- ALL. It may be a valuable option especially in patients with TCP-ALL, however it should be proved in prospective clinical trials.