Introduction: The prognosis of elderly patients with hematological malignancies by chemotherapy is usually poor. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) has remarkably improved long-term survival in this setting.

Aim: In present study, the outcomes of allo-HSCT in elderly patients with hematological malignancies by reduced-intensity conditioning (RIC) or myeloablative conditioning (MAC) are investigated. The risk factors for prognosis after allo-HSCT are also analyzed.

Methods: Between May 2019 and December 2024, 57 patients over 55 years with hematological malignancies who underwent allo-HSCT in our hospital were enrolled. The median age was 62 (55-73) years. The diagnosis were myelodysplastic syndrome (n=10), acute myeloid leukemia (AML, n=30), acute lymphoblastic leukemia (n=12), mixed phenotype acute leukemia (n=2), lymphoma (n=2) and chronic myelomonocytic leukemia (n=1). The disease status pre-transplant was complete remission (CR) in 31 (54.4%) cases and non-remission (NR) in 26 (45.6%) cases. The types of transplant included haploidentical (n=40, 70.2%), unrelated (n=11, 19.3%) and identical siblings (n=6, 10.5%). Nine cases were second allo-HSCT. Either RIC (n=16, 28.1%) or MAC (n=41, 71.9%) regimens was applied. Clinical charateristics between RIC and MAC cohorts have no significant difference. For RIC cohort, the regimen with total body irradiation (TBI, 6-7Gy, fractionated), fludarabine (30mg/m2, 5 days) and cytarabine (1g/m2, 3 days) was used. For MAC cohort, the regimen with TBI (8-10Gy, fractionated, n=15)/total marrow irradiation (10-12Gy, fractionated, n=2) or busulfan (0.8mg/kg q6h, 3 days, n=24), fludarabine (30mg/m2, 5 days) and cytarabine (1g/m2, 3 days) was used. Rabbit antithymocyte globulin was used in unrelated and haploidentical transplants. Cyclosporine, mycophenolate mofetil and short-term methotrexate were employed for graft-versus-host disease prophylaxis.

Results: Out of 57 patients, 56 achieved full donor chimerism because one patients with AML (NR in pre-transplant) had active disease at their first disease evaluation post-HSCT. The median time to neutrophil and platelet recovery was 14 (8-22) days, 13(8-32) days respectively. One patient who had early recurrence after transplantation did not achieve platelet engraftment. With a median follow-up of 12 (1-72) months, 1-year and 2-year overall survival (OS) rates were 62.59%, 60.36%, respectively; 1-year and 2-year disease-free survival (DFS) rates were 59.54%, 57.16%, respectively. One-year and 2-year OS in CR group were both 74.05%, while 1-year and 2-year OS in NR group were 48.70%, 42.61%, respectively. One-year and 2-year DFS in CR group were both 74.05%, while 1-year and 2-year DFS in NR group were 42.31%, 35.26%, respectively. Nineteen (26.3%) patients relapsed and 23 (40.4%) patients died. The causes of death included cerebral infarction (n=1), infections (n=8) and relapse (n=14). Transplant-related mortality (TRM) was 15.8%. With RIC regimen, TRM was significantly lower (6.3% vs. 22.0%, p=0.311), but relapse rate was higher (43.8% vs.19.5%, p=0.125) compared with that with MAC regimen. Therefore, no significant differences were found in OS (1-year OS: 61.88% vs. 62.87%, 2-year OS: 55.00%vs. 62.87%，p=0.5565) and DFS (1-year DFS: 56.25% vs. 60.88%, 2-year DFS: 49.22% vs. 60.88%，p=0.4139) between two cohorts. However, the disease status between NR and CR pre-HSCT had remarkable impact on OS (48.70% vs.74.05%, p=0.0114) and DFS (42.31% vs.74.05%, p=0.0035).

Conclusions: Under our protocol, OS and DFS have been improved remarkably by allo-HSCT in elderly patients with hematological malignancies, especially, the patients in CR pre-transplant have achieved 74.05% long-term DFS. Although RIC regimen has resulted in lower TRM, but the relapse rate was higher compared with MAC regimen, which transplanted into similar survival between two cohorts. The disease status pre-transplant was a key factor for prognosis of allo-HSCT in elderly patients with hematological malignancies.

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2025
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