---
title: "Sequential conditioning for hematopoietic stem cell transplant in elderly high-risk myeloid malign"
id: "frontiers-in-immunology-16-sequential-conditioning-in-hematopoietic-stem-cell-transplantation-in-elderly"
canonical_url: "https://medichelpline.com/clinical-feed/frontiers-in-immunology-16-sequential-conditioning-in-hematopoietic-stem-cell-transplantation-in-elderly"
content_type: "clinical_feed_article"
specialty: "Hematology"
source_name: "Frontiers in Immunology"
source_url: "https://www.frontiersin.org/articles/10.3389/fimmu.2026.1803250"
published_at: "2026-08-26T00:00:00.000Z"
evidence_level: "Journal Feed"
license: "CC-BY-NC-4.0 / Informational Use"
---
# Sequential conditioning for hematopoietic stem cell transplant in elderly high-risk myeloid malign
## Provenance & Clinical Metadata
- **Canonical URL:** https://medichelpline.com/clinical-feed/frontiers-in-immunology-16-sequential-conditioning-in-hematopoietic-stem-cell-transplantation-in-elderly
- **Specialty:** [Hematology](https://medichelpline.com/clinical-feed/hematology.md)
- **Primary Source:** Frontiers in Immunology
- **Source URL:** [Original Journal Publication](https://www.frontiersin.org/articles/10.3389/fimmu.2026.1803250)
- **Published At:** 2026-08-26T00:00:00.000Z
- **Evidence Rating:** Journal Feed
## Executive GIST (TL;DR)
- The provided source page and metadata indicate an article titled about **sequential conditioning** in **hematopoietic stem cell transplantation** (HSCT) for elderly patients with high-risk myeloid blood cancers, analyzing long-term survival, disease control, and immune recovery across donor types in a matched-pair analysis. - The source JINA body contains only Frontiers website navigation and page scaffolding; the article text, methods, numerical results, and conclusions were not available in the provided source content. - From the title alone, the study scope likely addresses outcomes after HSCT in an older, high-risk myeloid malignancy population, comparing donor types and evaluating **long-term survival**, **disease control**, and **immune reconstitution** following a sequential conditioning regimen. - The phrase “matched-pair analysis” in the title indicates a comparative design using matched pairs to control for confounders when comparing donor types or treatment groups; exact matching criteria were not reported in the source content. - Important details missing from the provided source include patient numbers, age range, diagnostic subtypes, conditioning regimen components and schedule, donor categories (related, unrelated, haploidentical, cord blood, etc.), follow-up duration, survival rates (overall survival, disease-free survival), relapse incidence, graft-versus-host disease rates, immune recovery metrics, and statistical analyses. - Because the article text and data were not present in the supplied content, no study-specific outcomes, effect sizes, or recommendations can be summarized or inferred without risking invention of facts. - Users seeking the full study should consult the original Frontiers in Immunology article at the provided URL for complete methods, results, tables, and authors’ conclusions.
## Clinical Analysis & Structured Key Points
Frontiers | Sequential conditioning in hematopoietic stem cell transplantation in elderly high-risk myeloid blood cancer patients: long-term survival, disease control, and immune recovery across donor types in a matched-pair analysis ORIGINAL RESEARCH article Front. Immunol. , 26 August 2026 Sec. Alloimmunity and Transplantation Volume 17 - 2026 | https://doi.org/10.3389/fimmu.2026.1803250 Published in Frontiers in Immunology Alloimmunity and Transplantation 7 impact factor 11.3 citescore Editor & Reviewers Edited by L C Luca Castagna Reviewed by P L Philippe Lewalle M S Miriam Sanchez Escamilla Outline Figures and Tables Figure 1 View in article Figure 2 View in article Figure 3 View in article Table 1 Patient characteristics. View in article Table 2 Donor and transplant characteristics. View in article Table 3 Immune reconstitution. View in article ORIGINAL RESEARCH article Front. Immunol. , 26 August 2026 Sec. Alloimmunity and Transplantation Volume 17 - 2026 | https://doi.org/10.3389/fimmu.2026.1803250 Sequential conditioning in hematopoietic stem cell transplantation in elderly high-risk myeloid blood cancer patients: long-term survival, disease control, and immune recovery across donor types in a matched-pair analysis S H Sarah Haebe 1 E S Elena Stauffer 1 H D Heidrun Drolle 1 D P Dusan Prevalsek 1 M S Moritz Schmidt 1 Q F Quentin Fichaux 1 M W Michael Weigand 2 A F Alessia Fraccaroli 1 † J T Johanna Tischer 1 † * 1. Department of Medicine III, Ludwig Maximilian University Hospital Munich, Munich, Germany 2. Institute of Laboratory Medicine, Ludwig Maximilian University Hospital, Munich, Germany Article metrics View details Abstract Background: Sequential conditioning allogeneic hematopoietic stem cell transplantation (allo-HSCT) regimens might offer improved disease control in high-risk myeloid patients. But concerns remain regarding toxicity, infection risk and delayed immune reconstitution (IR), particularly in older and HLA-haploidentical transplant recipients. To address these concerns, we comprehensively compared safety, feasibility and clinical outcome across HLA-matched related (MRD), matched unrelated (MUD) and haploidentical donor (Haplo) HSCT and longitudinally characterize IR patterns and their associations with post-transplant outcomes. Methods: We conducted a retrospective matched-pair analysis comparing MRD-, matched MUD- and Haplo-HSCT in elderly patients matched for (1) disease activity: p = 1.0; (2) disease status: p = 1.0; (3) modified disease risk index (DRI): p = 0.9; (4) hematopoietic cell transplantation comorbidity index (HCT-CI): p = 0.92; and (5) age: p = 0.95. Outcomes included disease-free (DFS) and overall survival (OS), relapse, non-relapse mortality (NRM), graft-versus-host disease (GvHD), toxicity, infections, and donor-specific IR dynamics and their impact on clinical outcomes. Results: With a median follow-up of more than 9 years, no significant differences were observed in long-term disease control and survival among the three groups (5-y DFS/OS: MRD = 41%/41%, MUD = 56%/63%, Haplo = 58%/58%; p = 0.52/0.55). Cumulative incidences (CI) of 5-y-NRM and 1-y moderate and severe chronic GvHD (cGvHD) rates were comparable among the three groups (NRM/cGvHD: MRD = 19%/13%, MUD = 29%/6%, Haplo = 18%/19%; p = 0.3/0.57). Overall immune cell recovery after one year was comparable among groups, though early recovery of CD3+ T and NK cells was delayed after Haplo-HSCT. Subgroup analysis revealed that higher early CD4+ T and lower B cell counts were associated with increased CI of acute GvHD III-IV° (p = 0.04/0.03). Additionally, NK recovery at one year was associated with improved DFS and OS as well as lower relapse incidence. Conclusions: Sequential therapy is safe and feasible in elderly patients with high-risk or active disease across all three transplant platforms. The observed associations between IR and clinical outcomes highlight the relevance of immune monitoring for anticipating post-transplant complications and guiding individualized prophylactic and therapeutic strategies. Prospective studies are needed to further investigate these findings and define the underlying mechanisms. Introduction Sequential regimens combining cytoreductive chemotherapy followed by reduced-intensity conditioning (RIC) have shown promising results in patients with high-risk myeloid disease, particularly acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) ( 1 , 2 ). This sequential approach offers effective leukemia control and reduced relapse rates in both HLA-matched and HLA-haploidentical (Haplo) hematopoietic stem cell transplantation (HSCT) settings ( 1 , 3 – 6 ). However, despite encouraging clinical outcomes, concerns remain regarding toxicity and infections with sequential conditioning approaches especially in older patients. Similarly, prior studies suggest an elevated infection risk following Haplo-HSCT ( 7 , 8 ). A crucial factor in determining clinical outcomes, and in particular infection rates, is immune reconstitution (IR) after allogeneic HSCT (allo-HSCT). IR is influenced by various factors including conditioning regimes, sex, age and graft-versus-host disease (GvHD) prophylaxis. Moreover, the type of donor is thought to significantly influence the pace and quality of IR. In HLA-matched HSCT, rapid IR offers protection against both infections and relapse ( 9 ). In contrast, Haplo-HSCT is generally associated with delayed IR compared to HLA-matched related donor (MRD) transplants ( 10 – 12 ). However, comparative data on IR across different transplant modalities and donor types – and in particular the influence of sequential conditioning - remain relatively sparse, largely due to limited granularity of IR data in transplant registries ( 13 ). Thus, whether sequential conditioning in the Haplo-HSCT setting compromises IR and increases the risk of infection remains unclear. This question is especially relevant in older patients, where treatment decisions must balance optimal disease control with potential infectious complications. To address this question, we conducted a retrospective matched-pair analysis comparing sequential conditioning MRD-, matched unrelated donor (MUD)-, and Haplo-HSCT in elderly patients with high-risk myeloid diseases. For better comparison across the three groups, our analysis accounted for confounding factors such as patient age, disease status and activity as well as co-morbidity indices. We evaluated long-term survival and disease-free outcomes as well as GvHD, toxicity, and infection profiles, along with a detailed comparison of cellular IR across the different donor types and its potential impact on clinical outcomes. Methods and materials Study design Eligible were older patients (≥ 50 years) with high-risk AML defined by either high-risk cytogenetics, relapsed/refractory AML or untreated secondary/therapy-related AML or high-risk MDS defined by adverse cytogenetics, who underwent their first sequential RIC transplantation at our center between January 2009 and June 2017 using an MRD, MUD (fully allele-match at HLA-A, HLA-B, HLA-C, HLA-DRB1 and HLA-DQB1 loci) or related, haploidentical donor (Haplo; mismatched for ≥ 2 HLA loci mentioned beforehand). Older patients were defined as ≥50 years due to their increased risk of toxicity with sequential conditioning regimens ( 14 ). Pre-defined matching criteria for this study included (i) disease activity (blast yes/no), (ii) disease status at start of sequential conditioning (relapse, refractory, high-risk), (iii) modified disease risk index (DRI ( 15 ), (iv) hematopoietic cell transplantation specific comorbidity index (HCT-CI), missing closing parentheses ( 16 ), and (v) age (+/-5years). The study was conducted in accordance with German legislation and the revised Helsinki declaration, and was evaluated and approved by the local ethics committee of the Ludwig-Maximilians University of Munich (#19-368). Written informed consent for participation in this retrospective study was obtained from all patients prior to transplantation. Conditioning and post-transplant management Sequential conditioning consisted of either FLAMSA (fludarabine 30 mg/m 2 , cytarabine 1–2 g/m 2 , amsacrine 100 mg/m 2 IV over 4 days) or clofarabine (30 mg/m 2 IV over 5 days) prior to RIC. HLA-typing, donor selection as well as supportive microbial prophylaxis were performed as previously described ( 1 ). In vivo T cell depletion with anti-thymocyte globulin (ATG) was used in the HLA-matched setting (3x10mg/kg in MRD-HSCT, 3x20 mg/kg in MUD-HSCT). Post-transplantation cyclophosphamide (PTCY) was applied in the haploidentical setting ( 17 ). Post-grafting immunosuppression consisted uniformly of a calcineurin inhibitor (CNI) and mycophenolate mofetil (MMF). In the HLA-matched setting, ciclosporin A was started on day –1 and MMF on day 0, with planned discontinuation at day +100. In the haploidentical setting, tacrolimus and MMF were both initiated on day +5, with scheduled discontinuation starting at day +150. Post-grafting G-CSF was administered only in the Haplo setting. Letermovir prophylaxis was not used routinely because it had not yet received regulatory approval in Germany at the time. Donor lymphocyte infusions (DLIs) were given in the absence of acute GvHD (aGvHD), either prophylactically or preemptively, for relapse prevention. Following the strategy described by Schmid et al. ( 18 ), prophylactic DLIs were given four weeks after cessation of immunosuppression. The timing of immunosuppression withdrawal varied according to the donor platform used. Definitions Genetic aberrations were classified according to the European LeukemiaNet (ELN) ( 19 ) or per revised international prognostic scoring system (IPSS-R) ( 20 ). Complete remission (CR) prior to allo-HSCT was defined according to standard morphologic criteria. Refractory was defined as disease persistence after induction chemotherapy regimen. Response rate was assessed at day +30 post HSCT through bone marrow (BM) aspiration and chimerism analysis. aGvHD was classified using the established criteria ( 21 , 22 ); chronic GvHD (cGvHD) was graded following the National Institutes of Health consensus criteria ( 23 , 24 ). GvHD-free/relapse-free survival (GRFS) and cGvHD-free/relapse-free survival (CRFS) were defined as previously described ( 25 ) and considered as secondary endpoints. Non-hematologic toxicities were scored according to National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE; version 5.0) from start of sequential therapy until day +30 post allo-HSCT. Immune reconstitution To characterize immune reconstitution, fresh peripheral blood samples collected at predefined time points prior to and after allo-HSCT (+30, +100, +180 and +360 days) were assessed using FACS Canto II flow cytometry (BD). The following fluorochrome-conjugated monoclonal antibodies were used for the identification of immune cell subsets: CD45 (clone 2D1, V500-C, BD), CD3 (clone SK7, APC-H7, BD), CD4 (clone SK3, PerCP-Cy5.5, BD), CD8 (clone SK1, FITC, BD), CD16 (clone B73.1, PE, BD), CD56 (clone MY31, PE, BD), and CD19 (clone SJ25C1, V450, BD). Leukocyte populations were initially gated based on CD45 expression (CD45+). Within this population, T cells were identified as CD3+ cells and further subdivided into CD4+ helper T cells (CD3+/CD4+) and CD8+ cytotoxic T cells (CD3+/CD8+). Natural killer (NK) cells were defined as CD3-/CD16+/CD56+ cells, and B cells were identified as CD19+ cells. Absolute counts and relative frequencies of these immune cell subsets were quantified at each time point to assess the kinetics of immune reconstitution following allo-HSCT. Statistical analysis Survival probabilities were estimated using the Kaplan-Meier method. Death from any cause was considered an event; surviving patients were censored at last follow-up. Cumulative incidence curves accounted for competing risks (e.g. aGvHD, cGvHD, non-relapse mortality (NRM), relapse) and were compared using Gray’s test. Patient and transplant characteristics were compared using the x 2 –test or Fisher’s exact test for categorical variables and the Kruskal-Wallis test for continuous variables. Continuous variables were reported as medians with ranges, categorical variables as percentages. Analyses of IR and its association with clinical endpoints were exploratory and hypothesis-generating. Reported p-values are descriptive and were not adjusted for multiple comparisons, and the possibility of chance findings cannot be excluded; cut-offs for IR markers were determined based on medians and/or quartiles. All tests were two-sided; P 2 19 (37) 6 (35) 7 (41) 6 (35) Patient characteristics. *Served as matching criteria. Values in parentheses represent percentages if not indicated otherwise. AML , acute myeloid leukemia; DRI , disease risk index; Haplo , haploidentical donor; HCT-CI score , hematopoietic cell transplantation-specific comorbidity index; MDS , myelodysplastic syndrome; MRD , matched related donor; MUD , matched unrelated donor; PIF , primary induction failure; sAML , secondary AML; tAML , therapy-related AML. Table 2 All MRD MUD Haplo P-value Patients 51 (100) 17 (100) 17 (100) 17 (100) Donor age < 0.01 Median (range) 39 (21-69) 57 (49-69) 34 (23-50) 29 (21-66) Donor sex 0.35 Male 29 (57) 8 (47) 12 (71) 9 (53) Donor sex-match 0.13 Patient male/donor female 9 (18) 6 (35) 1 (6) 2 (12) Patient female/donor male 15 (29) 5 (29) 4 (23) 6 (35) Match 27 (53) 6 (35) 12 (71) 9 (53) No of HLA mismatches < 0.01 Median (range) 0 (0-7) 0 (0) 0 (0) 5 (5-7) Time to allo-HSCT 0.37 Median months 2 (0-8) 2 (0-4) 2 (0-6) 2 (1-8) ABO match 28 (55) 12 (71) 4 (24) 12 (71) < 0.01 CMV match 37 (73) 15 (88) 11 (65) 11 (65) 0.30 Cytoreduction regimen 0.01 FLAMSA 47 (92) 17 (100) 17 (100) 13 (76) Clofarabine 4 (8) 0 (0) 0 (0) 4 (24) Stem cell source < 0.01 BM 9 (18) 0 (0) 0 (0) 9 (53) PBSC 42 (82) 17 (100) 17 (100) 8 (47) Median cell dose (range) n.a NCx10 8 /kg BW -– -– -– 2.7 (2-4) CD34x10 6 /kg BW 7.7(4-17) 9 (5-14) 8 (4-15) 5.6 (4-17) Conditioning 1.0 RIC 51 (100) 17 (100) 17 (100) 17 (100) TBI-based 19 (37) 10 (59) 5 (29) 4 (24) 0.07 Drug-based 32 (63) 7 (41) 12 (71) 13 (76) GvHD prophylaxis < 0.01 ATG-CsA-MMF 33 (65) 17 (100) 16 (94) 0 (0) ATG-Tac-MMF 1 (2) 0 (0) 1 (6) 0 (0) CY-Tac-MMF 17 (33) 0 (0) 0 (0) 17 (100) Year of transplant 0.92 Median 2013 2013 2012 2013 Donor and transplant characteristics. Values in parentheses represent percentages if not indicated otherwise. ATG , anti-thymocyte globulin; BM , bone marrow; BW , body weight; CMV , cytomegalovirus; CsA , ciclosporin A; CY , cyclophosphamide; Haplo , haploidentical donor; HLA , human leukocyte antigen; kg , kilogram; MMF , mycophenolate mofetil; MRD , matched related donor; MUD , matched unrelated donor; NC , nucleated cells; PBSC , peripheral blood stem cells; RIC , reduced intensity conditioning; Tac , tacrolimus; TBI , total body irradiation. Engraftment and DLI No primary graft rejection occurred ( Supplementary Table 1 ). Primary neutrophil engraftment was achieved in all but three patients – two with autologous recovery and persistence of blasts (MRD:1, MUD:1) and one early death in aplasia post Haplo-HSCT. Platelet recovery was significantly delayed in the Haplo-HSCT (Haplo: 40, MRD: 13, MUD: 19 days; p<0.01). Regarding DLI application, four patients were able to receive DLIs (MRD: 2; MUD: 2). All other patients were not eligible for prophylactic DLI because of either early death/early relapse (n = 9), history of or ongoing GvHD including overall grade II aGvHD requiring systemic steroid treatment (n = 34), or recurrent infections (n = 4). Immune reconstitution Pre-transplant lymphocyte subsets were comparable across transplantation platforms ( Table 3 ). By day +30, absolute lymphocyte counts (ALC) were significantly lower in Haplo recipients receiving PTCY compared with ATG-treated MRD/MUD patients (p<0.01), however normalized by one year post-HSCT. Differences in ATG dosing between the MRD and MUD groups were not associated with differences in early ALC recovery. Table 3 MRD MUD Haplo P-value Global P-value MRD vs MUD/MRD vs Haplo/ MUD vs Haplo Pre-Transplantion CD45+ 900 1090 855 0.63 0.46/0.40/0.75 CD3+ 810 740 690 0.52 0.37/0.31/0.88 CD3+/CD4+ 380 400 285 0.45 0.94/0.33/0.25 CD3+/CD8+ 360 250 260 0.27 0.12/0.29/0.72 CD16+/CD56+ 80 130 130 0.45 1.00/0.22/0.38 CD19+ 70 40 50 0.81 0.50/0.73/0.90 Day +30 CD45+ 480 520 195 0.02 1.0/<0.01/0.01 CD3+ 410 245 115 0.11 0.76/0.04/0.15 CD3+/CD4+ 55 25 50 0.40 0.20/0.44/0.57 CD3+/CD8+ 200 160 45 0.20 0.44/0.08/0.37 CD16+/CD56+ 150 160 30 0.08 0.82/0.09/0.04 CD19+ 10 10 7 0.45 0.80/0.58/0.22 Day +100 CD45+ 1168 675 510 0.09 0.20/0.02/0.50 CD3+ 750 260 130 0.01 0.07/<0.01/0.17 CD3+/CD4+ 135 34 70 0.36 0.19/0.25/0.87 CD3+/CD8+ 490 181 85 0.07 0.12/0.02/0.45 CD16+/CD56+ 275 185 250 0.85 0.56/0.81/0.82 CD19+ 50 17 45 0.65 0.54/0.96/0.37 Day +180 CD45+ 1650 990 1010 0.13 0.09/0.08/0.84 CD3+ 1488 420 450 0.06 0.09/0.03/0.45 CD3+/CD4+ 180 190 120 0.41 0.43/0.26/0.46 CD3+/CD8+ 855 240 320 0.21 0.17/0.10/0.82 CD16+/CD56+ 230 200 340 0.50 0.74/0.52/0.26 CD19+ 250 70 160 0.43 0.31/0.31/0.53 Day +360 CD45+ 1500 1710 1200 0.79 0.44/0.75/0.95 CD3+ 830 750 620 0.92 0.80/0.95/0.70 CD3+/CD4+ 180 150 170 0.69 0.55/0.65/0.46 CD3+/CD8+ 590 300 470 0.71 0.46/0.75/0.60 CD16+/CD56+ 200 250 220 0.35 0.23/0.27/0.66 CD19+ 165 160 195 0.38 0.66/0.17/0.50 Immune reconstitution. Haplo , haploidentical donor; MRD , matched related donor; MUD , matched unrelated donor. Focusing on day +30 on total CD3+ T cells, the counts were markedly reduced after PTCY (median 115/µl) compared to MUD (245/µl) and MRD (410/µl; Table 3 ). The largest divergence between platforms occurred at day +100, with MRD re
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