Survival trends in young adults with acute leukaemia after AHSCT in Germany: comparisons with younger and older patients.

[BACKGROUND] Despite increasing cancer survival for young adults (YA), previous studies have shown poorer survival in YA compared to children for acute leukaemia.

[OBJECTIVES] This study aims to present the survival outcomes of patients with acute myeloid leukaemia (AML) or acute lymphoblastic leukaemia (ALL) following an initial allogeneic haematopoietic stem cell transplantation (AHSCT), categorised by age. To this end, the survival outcomes, particularly overall survival (OS), of young adults aged 18-39 years were analysed in comparison with those of younger or older patients.

[STUDY DESIGN] For this purpose, the databases of the German registries for pediatric and adult hematopoietic stem cell transplantation and cellular therapy (PRSZT and DRST) were screened for patients with first AHSCT between 2011-2019. Patients after first AHSCT or without consent to report data were excluded. For all endpoints, YA were categorized between 13-17 and 40-59 year-old patients. We calculated 5-year OS / event-free survival (EFS) / graft-versus-host-disease-free-relapse-free survival (GFRS) probabilities separately for AML, ALL, age-subgroups, and sex.

[RESULTS] Out of a total of 8,834 (78.5%) patients with AML and 2,424 (21.5%) patients with ALL, 1,276 (11.3%) and 882 (7.8%) young adults, respectively, were included. Of those, the 5-year OS/EFS/GFRS probabilities were 57%/46%/37% for AML and 53%/49%/35% for ALL. The corresponding 5-year-non-relapse mortality (NRM)/relapse incidence were 12%/40% and 19%/31%, respectively. In particular, YA with AML showed an improvement in NRM during the observation period, HR 0.897 [0.828; 0.972].

[CONCLUSIONS] While AHSCT seemed to balance survival differences between AML and ALL, children and adolescents benefited most. Survival differences between pediatric and adult patients are likely due to different donor selection and conditioning strategies. However, patient outcomes improved over time of AHSCT, for all age groups. In addition, relapse and non-relapse mortality increase with age and the mortality rate for males was significantly higher than that for females with acute leukemia after AHSCT. Although relapse and NRM increased with age, NRM tended to improve, especially in YA. Further investigations with a longer follow-up are needed to clarify differences in age-related survival between the diseases.