Impact of Donor Type on Long-Term Outcomes of Hematopoietic Cell Transplantation for Adult Acute Lymphoblastic Leukemia during First Remission

Abstract

Background: Standard therapy for adult patients with high-risk acute lymphoblastic leukemia (ALL) consists of hematopoietic cell transplantation (HCT) including autologous-HCT (AUTO) and allogeneic-HCT from a matched-sibling donor (MSD) or matched unrelated donor (MUD). When a conventional donor is not available, HCT from a partially-mismatched unrelated donor (MMUD), cord blood transplantation (CBT) or a familial haploidentical donor (HID) is considered.Aim: Although HCT outcomes of those alternative strategies are advancing with optimization of pre-conditioning regimens with immunosuppressive agents, there are still subjects to debate. We tried to analyze the long-term HCT outcomes according to the donor types including MMUD, double CBT (DCBT) and AUTO as an alternative choice compared to the conventional donors.Methods: We enrolled 661 adult ALL patients who underwent transplantation from 1995 to 2015 in their first remission (CR1). Patients with acute undifferentiated leukemia (AUL, n=5) and mixed phenotype acute leukemia (MPAL, n=52) in the same department were also enrolled and median age was 33 years old (range, 15-65). Before 2010, our treatment strategy for ALL patients in CR1 was to offer allogeneic or autologous HCT according to the donor availability and the presence of high-risk features. After 2010, DCBT was mainly used for patients who were not available with conventional donors. For myeloablative regimen, we administered cyclophosphamide (120 mg/kg) combined with TBI (1320 cGy), and reduced intensity regimen was applied for elderly or patients with comorbid conditions which consisted of fludarabine (150 mg/m2 in total) and melphalan (140 mg/m2 in total). Conditioning regimen for AUTO was TBI (1200 cGy), ARA-C (9g/m2 in total) and melphalan (100mg/m2 in total), and fludarabine (150mg/m2 in total) was used for DCBT instead of melphalan. Graft-versus-host disease (GVHD) prophylaxis was attempted by administering calcineurin inhibitors (cyclosporine for MSD, tacrolimus for others) plus methotrexate or mycophnolate mofetil (for DCBT). Antithymocyte globulin (ATG) was administered to the patients who received grafts from MMUD.Results: Engraftment was successful in all donor types, but neutrophil and platelet recovery was significantly delayed only after DCBT (median recovery for neutrophil and platelet was 25 and 33.5 days respectively). After median follow-up of 80.4 months (range, 6.5-259.1), 7-year OS for the entire 661 patients was 57.0%. In detail, 7-year OS for MSD, MUD, MMUD, DCBT, and AUTO was 56.9%, 56.8%, 62.6%, 65.1% and 48.6% (p=0.423). MSD, MUD and MMUD showed similar relapse rate (27.5%) and non-relapse mortality (NRM) rate (20.6%), but DCBT showed significantly higher NRM rate (29.6%) and AUTO showed significantly higher relapse rate (41.6%). In contrast, DCBT showed lower relapse rate (7.2%) and AUTO showed lower NRM rate (9.7%). Interestingly, 7-year GVHD and relapse-free survival (GRFS) for MSD, MUD, MMUD, and DCBT was 34.1%, 15.0%, 40.9%, and 50.3%, respectively, which was related with higher incidence of severe chronic GVHD in MUD (27.6%) and MSD (14.1%) compared to DCBT (4.2%, p < 0.001). In high-risk subgroup (n=517) including 233 Philadelphia chromosome (Ph)-positive ALL, 7-year OS for MSD, MUD, MMUD, DCBT, and AUTO was 54.9%, 58.1%, 57.8%, 60.7%, and 33.3%, respectively. But the 7-year GRFS for MSD, MUD, MMUD, and DCBT was 30.7%, 14.5%, 35.3%, and 47.7%, respectively, which revealed lower relapse rate (8.7%) and low severe chronic GVHD (2.6%) of DCBT. Multivariate analysis showed that old age and AUTO was related with poor OS in high-risk ALL patients group, and old age and poor-risk karyotype and MUD transplant without ATG were related with poor GRFS.Conclusion: Our data showed similar transplant outcomes of alternative donors such as DCBT and ATG-applied MMUD compared to conventional donor transplants in ALL patients in CR1. In addition, GRFS was rather superior in patients treated with DCBT. Our long-term transplantation outcome results revealed that DCBT might be a good alternative choice for patients who are not available with conventional allogeneic donors, and AUTO may be considered for selected standard-risk patients with low NRM rate without a risk of GVHD. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.