Allogeneic Hematopoietic Stem Cell Transplantation for Older Patients with Hematological Malignancies

Allogeneic hematopoietic stem cell transplantation (allo-HCT) has been established as a curative treatment for hematological malignancies such as acute myeloid leukemia and myelodysplastic syndrome. Patients aged ≥ 70 years have traditionally been considered ineligible for this procedure, because of concerns over high transplant-related mortality rates and difficulties managing post-transplant complications. However, recent advances in supportive care, expanded donor availability, and the development of reduced-intensity conditioning (RIC) regimens have increased the availability of allo-HCT for older patients. Notably, the number of allo-HCT procedures performed in patients aged ≥ 70 has been steadily increasing in Japan and Western countries, reflecting a re-evaluation of transplant eligibility in older patients. When assessing transplant eligibility in older patients, it is crucial to consider not only disease risk stratification and treatment response, but also comprehensive evaluations of general health status, comorbidities, cognitive function, and social backgrounds. In particular, indexes such as the Hematopoietic Cell Transplantation-Comorbidity Index and Comprehensive Geriatric Assessment have proven useful for predicting patient prognoses and non-relapse mortality. Donor selection and the intensity of the conditioning regimen used can both significantly influence transplant outcomes. RIC or non-myeloablative regimens are generally recommended for patients aged ≥ 70 years. Human leukocyte antigen-matched related or younger unrelated donors are preferred, while haploidentical donors or cord blood may be considered when matched donors are unavailable, although evidence in older patients is limited. This review provides a comprehensive overview of the current status of and challenges related to allo-HCT in patients aged ≥ 70 years. Patient eligibility, conditioning strategies, donor selection, and transplant outcomes are discussed in detail, based on the latest available evidence.