Dose intensity for conditioning in allogeneic hematopoietic cell transplantation: can we recommend "when and for whom" in 2021?

Reduced toxicity (FluBu3) versus myeloablative (BuCy) conditioning in acute myeloid leukemia patients who received first allogeneic hematopoietic stem cell transplantation in measurable residual disease-negative CR1

In the present study, reduced toxicity (FluBu3) and myeloablative (BuCy) conditioning were compared in patients with AML who received first allogeneic HSCT in MRD-negative CR1. The study included 124 adult patients who underwent HSCT from an HLA-matched (8/8) sibling, unrelated, or 1-locus mismatched (7/8) unrelated donor (MMUD). The median age was 45 years and intermediate cytogenetics comprised majority (71.8%). The 2-year OS, RFS, CIR and NRM for BuCy (n = 78, 62.9%) and FluBu3 (n = 46, 37.1%) groups were 78.3% and 84.5% (p = 0.358), 78.0% and 76.3% (p = 0.806), 7.7% and 21.5% (p = 0.074) and 14.3% and 2.2% (p = 0.032), respectively. At the time of data cut-off, relapse and NRM were the main causes of HSCT failure in each of the FluBu3 and BuCy arms. Among patients, 75% of relapsed FluBu3 patients had high-risk features of either poor cytogenetics or FLT3-ITD mutation compared with 16.7% of BuCy patients. The majority of NRM in the BuCy group was due to GVHD (73%), half of whom received MMUD transplantation. To conclude, the FluBu3 reduced toxicity conditioning showed comparable post-transplant OS and RFS to BuCy and was associated with significantly reduced NRM that was offset by a trend towards higher risk of relapse even in MRD-negative CR1 population.

Management of adult patients with CMML undergoing allo-HCT: recommendations from the EBMT PH&G Committee

ABSTRACT

Chronic myelomonocytic leukemia (CMML) is a heterogeneous disease presenting with either myeloproliferative or myelodysplastic features. Allogeneic hematopoietic cell transplantation (allo-HCT) remains the only potentially curative option, but the inherent toxicity of this procedure makes the decision to proceed to allo-HCT challenging, particularly because patients with CMML are mostly older and comorbid. Therefore, the decision between a nonintensive treatment approach and allo-HCT represents a delicate balance, especially because prospective randomized studies are lacking and retrospective data in the literature are conflicting. International consensus on the selection of patients and the ideal timing of allo-HCT, specifically in CMML, could not be reached in international recommendations published 6 years ago. Since then, new, CMML-specific data have been published. The European Society for Blood and Marrow Transplantation (EBMT) Practice Harmonization and Guidelines (PH&G) Committee assembled a panel of experts in the field to provide the first best practice recommendations on the role of allo-HCT specifically in CMML. Recommendations were based on the results of an international survey, a comprehensive review of the literature, and expert opinions on the subject, after structured discussion and circulation of recommendations. Algorithms for patient selection, timing of allo-HCT during the course of the disease, pretransplant strategies, allo-HCT modality, as well as posttransplant management for patients with CMML were outlined. The keynote message is, that once a patient has been identified as a transplant candidate, upfront transplantation without prior disease-modifying treatment is preferred to maximize chances of reaching allo-HCT whenever possible, irrespective of bone marrow blast counts.

Impact of busulfan versus treosulfan dose intensity in myelofibrosis undergoing hematopoietic cell transplantation

One key aspect of allogeneic hematopoietic cell transplantation (HCT) is pretransplant conditioning, balancing risk for relapse versus non-relapse mortality. Conditioning regimens with different alkylators at different doses can influence outcome, but data are missing for myelofibrosis, a challenging cohort of patients usually presenting at older age and with comorbidities. We evaluated in a multicenter retrospective study the comparative efficacy and safety of busulfan versus treosulfan in combination with fludarabine for myelofibrosis patients undergoing HCT. This study included 1115 patients (busulfan, n = 902; treosulfan, n = 213) receiving first HCT between 2005 and 2021. Patients were generally balanced for key patient characteristics. Overall survival at 4 years was 62% for the busulfan group versus 58% for the treosulfan group (p = .22). Impact on outcome was dose-dependent. Overall survival was 65% (95% CI, 61%-69%) for reduced intensity busulfan versus 69% (95% CI, 54%-84%) for reduced intensity treosulfan, 53% (95% CI, 44%-63%) for higher intensity busulfan, and 55% (95% CI, 46%-63%) for higher intensity treosulfan. Incidence of relapse was similar across intensity groups. In multivariable analysis, the hazard for death (with reduced intensity busulfan as reference) was 0.88 (95% CI, 0.39-2.01) for reduced intensity treosulfan (p = .77), 1.42 (95% CI, 0.96-2.10) for higher intensity busulfan (0.08), and 1.61 (95% CI, 1.14-2.26) for higher intensity treosulfan (p = .006). In terms of non-relapse mortality, comparison was not significantly different, while the hazard ratio for higher intensity treosulfan was 1.48 (95% CI, 0.98-2.23; p = .06). Here, we showed comparable outcomes and improved survival in myelofibrosis undergoing HCT with reduced intensity busulfan or treosulfan.

Splenic irradiation for myelofibrosis prior to hematopoietic cell transplantation: A global collaborative analysis

Splenomegaly is the clinical hallmark of myelofibrosis. Splenomegaly at the time of allogeneic hematopoietic cell transplantation (HCT) is associated with graft failure and poor graft function. Strategies to reduce spleen size before HCT especially after failure to Janus kinase (JAK) inhibition represent unmet clinical needs in the field. Here, we leveraged a global collaboration to investigate the safety and efficacy of splenic irradiation as part of the HCT platform for patients with myelofibrosis. We included 59 patients, receiving irradiation within a median of 2 weeks (range, 0.9-12 weeks) before HCT. Overall, the median spleen size prior to irradiation was 23 cm (range, 14-35). Splenic irradiation resulted in a significant and rapid spleen size reduction in 97% of patients (57/59), with a median decrease of 5.0 cm (95% confidence interval, 4.1-6.3 cm). The most frequent adverse event was thrombocytopenia, with no correlation between irradiation dose and hematological toxicities. The 3-year overall survival was 62% (95% CI, 48%-76%) and 1-year non-relapse mortality was 26% (95% CI, 14%-38%). Independent predictors for survival were severe thrombocytopenia and anemia before irradiation, transplant-specific risk score, higher-intensity conditioning, and present portal vein thrombosis. When using a propensity score matching adjusted for common confounders, splenic irradiation was associated with significantly reduced relapse (p = .01), showing a 3-year incidence of 12% for splenic irradiation versus 29% for patients with immediate HCT and 38% for patients receiving splenectomy. In conclusion, splenic irradiation immediately before HCT is a reasonable approach in patients experiencing JAK inhibition failure and is associated with a low incidence of relapse.

Reduced-intensity allogenic transplantation for children and adolescents with Philadelphia chromosome-positive acute lymphoblastic leukemia

Survival rates of patients with Philadelphia chromosome-positive ALL (Ph+ALL) have improved considerably with the introduction of tyrosine kinase inhibitors (TKI); however, hematopoietic stem cell transplantation (HSCT) continues to play an important role. Reduced-intensity conditioning (RIC) regimens have been widely applied particularly for older patients, but their validity for children and adolescents with Ph+ALL has not been investigated. In this study, data from patients receiving HSCT for de novo Ph+ALL in first or second remission at ages younger than 25 years and with a history of pre-HSCT TKI therapy were retrospectively collected through the nationwide registry in Japan. In 265 patients who received myeloablative conditioning (MAC) and 33 patients receiving RIC, 5-year leukemia-free survival (LFS) rates were 67.3% and 79.8%, respectively (p = 0.142). Multivariate analysis of LFS, focusing on patients with good performance status, identified RIC as a significant prognostic factor for LFS (hazard ratio 0.32, p = 0.032), as well as older age, higher leukocyte count at diagnosis, and disease with additional chromosomal abnormalities. These trends were similar when we focused on patients who received prophylactic post-HSCT TKI treatment, as 5-year LFS was 81.0% for MAC and 84.4% for RIC (p = 0.748). In summary, HSCT with RIC regimen showed at least comparable LFS to HSCT with MAC regimen, and RIC was an independent favorable prognostic factor on multivariate analysis adjusting potential prognostic factors. While patient numbers were limited, our data suggest that RIC may be safely applied in this group, particularly combined with prophylactic post-HSCT TKI maintenance therapy.

Advances in HIV Gene Therapy

Early gene therapy studies held great promise for the cure of heritable diseases, but the occurrence of various genotoxic events led to a pause in clinical trials and a more guarded approach to progress. Recent advances in genetic engineering technologies have reignited interest, leading to the approval of the first gene therapy product targeting genetic mutations in 2017. Gene therapy (GT) can be delivered either in vivo or ex vivo. An ex vivo approach to gene therapy is advantageous, as it allows for the characterization of the gene-modified cells and the selection of desired properties before patient administration. Autologous cells can also be used during this process which eliminates the possibility of immune rejection. This review highlights the various stages of ex vivo gene therapy, current research developments that have increased the efficiency and safety of this process, and a comprehensive summary of Human Immunodeficiency Virus (HIV) gene therapy studies, the majority of which have employed the ex vivo approach.

DNA methylation of hematopoietic stem/progenitor cells from donor peripheral blood to patient bone marrow: implications for allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (AHSCT) is a life-saving treatment for selected hematological malignancies. So far, it remains unclear whether transplanted hematopoietic stem/progenitor cells (HSPCs) undergo epigenetic changes upon engraftment in recipient bone marrow (BM) after AHSCT and whether these changes might be useful in the transplant diagnostics. The purpose of this study was to characterize the whole genome methylation profile of HSPCs following AHSCT. Moreover, the relationship between the observed methylation signature and patient outcome was analyzed. Mobilized peripheral blood (mPB)-HSPCs from seven donors and BM-HSPCs longitudinally collected from transplanted patients with hematological malignancies up to one year from AHSCT (a total of twenty-eight samples) were analyzed using DNA methylation based-arrays. The obtained data showed that DNA methylation of mPB-HSPCs differs between young and adult donors and changes following HSPC engraftment in the BM of recipient patients. Looking at methylation in promoter regions, at 30 days post-AHSCT, BM-HSPCs showed a higher number of differentially methylated genes (DMGs) compared to those of mPB-HSPCs, with a prevalent hyper-methylation. These changes were maintained during all the analyzed time points, and methylation became like the donors after one year from transplant. Functional analysis of these DMGs showed an enrichment in cell adhesion, differentiation and cytokine (interleukin-2, -5 and -7) production and signaling pathways. Of note, DNA methylation analysis allowed to identify a potential "cancer/graft methylation signature" of transplant failure. It was evident in the latest available post-transplant BM-HSPC sample (at 160 days) and surprisingly already in early phase (at 30 days) in patients whose transplant was doomed to fail. Overall, the analysis of HSPC methylation profile could offer useful prognostic information to potentially assess engraftment success and predict graft failure in AHSCT.

How I treat transplant-eligible patients with myelofibrosis

Despite the approval of Janus kinase inhibitors and novel agents for patients with myelofibrosis (MF), disease-modifying responses remain limited, and hematopoietic stem cell transplantation (HSCT) remains the only potentially curative treatment option. The number of HSCTs for MF continues to increase worldwide, but its inherent therapy-related morbidity and mortality limit its use for many patients. Furthermore, patients with MF often present at an older age, with cytopenia, splenomegaly, and severe bone marrow fibrosis, posing challenges in managing them throughout the HSCT procedure. Although implementation of molecular analyses enabled improved understanding of disease mechanisms and subsequently sparked development of novel drugs with promising activity, prospective trials in the HSCT setting are often lacking, making an evidence-based decision process particularly difficult. To illustrate how we approach patients with MF with respect to HSCT, we present 3 different clinical scenarios to capture relevant aspects that influence our decision making regarding indication for, or against, HSCT. We describe how we perform HSCT according to different risk categories and, furthermore, discuss our up-to-date approach to reduce transplant-related complications. Last, we show how to harness graft-versus-MF effects, particularly in the posttransplant period to achieve the best possible outcomes for patients.

Updates in hematopoietic cell transplant and cellular therapies that enhance the risk for opportunistic infections

BACKGROUND

Infectious disease physicians may be asked to evaluate and manage a variety of infections in immunocompromised hosts undergoing hematopoietic cell transplant (HCT) and cellular therapies. Over the last decade, several advances in cellular therapy have occurred, with implications for the types of infectious complications that may be seen.

AIMS

The purpose of this review is to update the infectious disease physician on newer advances in HCT and cellular therapy, including haploidentical transplant, expanding indications for transplant in older individuals and children, and chimeric antigen receptor T-cells. We will review how these advances might influence infectious disease complications following HCT. We will also provide a perspective that infectious disease physicians can use to evaluate the degree of immune suppression in an individual patient to help determine the type of infections that may be encountered.

Dynamics of polyclonal immuno-reconstitution after allogeneic transplant with post-transplant cyclophosphamide and letermovir

Cytomegalovirus (CMV) reactivations are strong stimulators of immune-reconstitution (IR) in hematopoietic stem cell transplantation (HSCT) recipients. Herein, we analyzed 317 CMV-seropositive consecutive patients (n = 109 letermovir, LTV; n = 208 no-LTV), undergoing HSCT with post-transplant cyclophosphamide (PTCy) and calcineurin inhibitor- (CNI) free graft-versus-host-disease (GvHD) prophylaxis. At day+90, median CD19+/mm3 was higher in LTV-cohort: 5.5 [0;439] versus 2 [0;294], p = 0.008; median CD3+/mm3 counts were lower in LTV-cohort, with no differences in CD4+, CD8+ and NK-cells. At day+180 median CD3+, CD4+ and CD8+/mm3 values were comparable between groups. Higher CD19+/mm3 counts were observed in LTV-cohort: 62 [0; 2983] versus 42 [0; 863]. Significantly higher median NK/mm3 values were seen in LTV-cohort: 225.5 [0;763] versus 163.5 [0;1181], p = 0.0003. The impact of LTV on B-cell IR at 3 months and NK-cell levels at 6 months was retained in multivariate analysis (p < 0.01), whereas the effect on T-cells was not confirmed. Moreover, we confirmed a significant reduction of clinically-relevant CMV, and moderate-to- severe chronic GvHD in LTV-cohort. Overall, in our study the use of LTV was associated with a slight improvement of B-cell and NK-cells reconstitution, with only minor impact on T-cell subsets, giving new insights on polyclonal IR for HSCT recipients in the LTV era.

External validation and extended application of the transplant conditioning intensity score in acute myeloid leukemia

This study aimed to validate the utility of the transplant conditioning intensity (TCI) score in 1714 patients with acute myeloid leukemia (AML) undergoing allogeneic bone marrow or peripheral blood stem cell transplantation (BMT/PBSCT) and assess its applicability to 753 patients with AML undergoing umbilical cord blood transplantation (UCBT) both during first complete remission. Patients classified into a high TCI group accounted for 63% and 56% in the BMT/PBSCT and UCBT cohorts, respectively. In the BMT/PBSCT cohort, the risk of relapse was lower in patients in the high versus intermediate TCI group (P = 0.002), although non-relapse mortality (NRM) did not differ among the three TCI groups. In the UCBT cohort, both relapse and NRM did not differ among the TCI groups. Increasing cutoff points for intermediate and high TCI categories significantly improved the ability to predict relapse and NRM in the BMT/PBSCT cohort (P = 0.030 and 0.006, respectively), and relapse but not NRM in the UCBT cohort (P = 0.005 and 0.364, respectively). These findings highlight the difference in the threshold level of the TCI score for outcome discrimination between European and Japanese cohorts. The TCI scheme appears less effective for UCBT than for BMT/PBSCT.

Human herpesvirus 6-specific T-cell immunity in allogeneic hematopoietic stem cell transplant recipients

Human herpesvirus 6 (HHV-6) can reactivate after allogeneic hematopoietic stem cell transplant (allo-HSCT) and may lead to severe symptoms. HHV-6-specific immune responses after HSCT are largely unexplored. We conducted a prospective observational study on 208 consecutive adult patients who received allo-HSCT to investigate HHV-6 reactivations and specific immune responses. Interferon gamma-producing HHV-6-specific T cells were quantified using enzyme-linked immunospot assay (ELISpot). HHV-6 reactivation occurred in 63% of patients, at a median of 25 days from allo-HSCT. Only 40% of these presented a clinically relevant infection, defined by the presence of classical HHV-6 end-organ diseases (EODs), based on European Conference on Infections in Leukaemia (ECIL) guidelines, and other possible HHV6-related EODs. Using multivariate analysis, we identified risk factors for HHV-6 reactivation: previous allo-HSCT, posttransplant cyclophosphamide (PT-Cy), and time-dependent steroids introduction. The use of PT-Cy and steroids were associated with clinically relevant infections, whereas higher CD3+ cell counts seemed to be protective. Interestingly, circulating HHV-6-specific T cells were significantly higher in patients with reactivated virus. Moreover, HHV-6-specific T-cell responses, quantified at >4 days after the first viremia detection, predicted clinically relevant infections (P < .0001), with higher specificity (93%) and sensitivity (79%) than polyclonal CD3+ cells per μL. Overall survival and transplant-related mortality were not affected by time-dependent HHV-6 reactivation, whereas a significant association was observed between clinically relevant infections and acute graft-versus-host disease. These results shed light on the role of HHV-6 in allo-HSCT and may affect HHV-6 monitoring and treatment.

Diagnostic efficiency of metagenomic next-generation sequencing for suspected infection in allogeneic hematopoietic stem cell transplantation recipients

Introduction

Immunosuppression predisposes allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients to infection. Prompt and accurate identification of pathogens is crucial to optimize treatment strategies. This multi-center retrospective study aimed to assess the ability of metagenomic next-generation sequencing (mNGS) to detect causative pathogens in febrile allo-HSCT recipients and examined its concordance with conventional microbiological tests (CMT).

Methods

We performed mNGS and CMT on samples obtained from 153 patients with suspected infection during allo-HSCT. Patients were grouped based on their neutropenic status at the time of sampling.

Results

The mNGS test was more sensitive than CMT (81.1% vs. 53.6%, P<0.001) for diagnosing clinically suspected infection, especially in the non-neutropenia cohort. mNGS could detect fungi and viruses better than bacteria, with a higher sensitivity than CMT. Immune events were diagnosed in 57.4% (35/61) of the febrile events with negative mNGS results, and 33.5% (48/143) with negative CMT results (P=0.002). The treatment success rate of the targeted anti-infection strategy was significantly higher when based on mNGS than on empirical antibiotics (85% vs. 56.5%, P=0.004).

Conclusion

The mNGS test is superior to CMT for identifying clinically relevant pathogens, and provides valuable information for anti-infection strategies in allo-HSCT recipients. Additionally, attention should be paid to immune events in patients with negative mNGS results.

Novel risk assessment for the intensity of conditioning regimen in older patients

Reduced-intensity conditioning (RIC) regimens have long-term outcomes that are generally comparable with those of myeloablative conditioning (MAC) because of a lower risk of nonrelapse mortality (NRM) but a higher risk of relapse. However, it is unclear how we should select the conditioning intensity in individual cases. We propose the risk assessment for the intensity of conditioning regimen in elderly patients (RICE) score. We retrospectively analyzed 6147 recipients aged 50 to 69 years using a Japanese registry database. Based on the interaction analyses, advanced age (≥60 years), hematopoietic cell transplantation-specific comorbidity index (≥2), and umbilical cord blood were used to design a scoring system to predict the difference in an individual patient's risk of NRM between MAC and RIC: the RICE score, which is the sum of the 3 factors. Zero or 1 implies low RICE score and 2 or 3, high RICE score. In multivariate analyses, RIC was significantly associated with a decreased risk of NRM in patients with a high RICE score (training cohort: hazard ratio [HR], 0.73; 95% confidence interval [CI], 0.60-0.90; P = .003; validation cohort: HR, 0.57; 95% CI, 0.43-0.77; P < .001). In contrast, we found no significant differences in NRM between MAC and RIC in patients with a low RICE score (training cohort: HR, 0.99; 95% CI, 0.85-1.15; P = .860; validation cohort: HR, 0.81; 95% CI, 0.66-1.01; P = .061). In summary, a new and simple scoring system, the RICE score, appears to be useful for personalizing the conditioning intensity and could improve transplant outcomes in older patients.

Splenic irradiation prior to allogeneic transplant conditioning in myelofibrosis: A pilot experience

INTRODUCTION

In the era of JAK inhibitors, allogeneic stem cell transplantation (HSCT) remains the only curative treatment for patients with Myelofibrosis (MF). Splenic irradiation (SI) may be used to reduce spleen size and related symptoms.

METHODS

We conducted a retrospective analysis on 14 patients with MF who underwent HSCT with SI from any donor source at our center between June 2016 and March 2021. All patients received a conditioning backbone based on treosulfan and fludarabine, with post-transplant cyclophosphamide (PTCy) and sirolimus as graft-versus-host disease (GvHD) prophylaxis. Patients received SI with 10 Gy involved-field radiotherapy in five 2-Gy fractions over the course of a week prior to the beginning of conditioning.

RESULTS

At transplant all patients were transfusion-dependent and had splenomegaly (median bipolar diameter by ultrasound: 20.75 cm). Overall, 12 patients had received ruxolitinib prior to transplant. Re-evaluation of spleen dimensions was available for 13 patients: median splenic bipolar diameter after at least 3 months from transplant decreased by a median of 25%. With a median post-transplant follow-up of 25 months, 6 patients remain in CR with full-donor chimerism, 3 patients died due to NRM. Overall, 4 patients relapsed. At last follow-up, nine patients are currently alive and achieved transfusion-independence.

CONCLUSIONS

In a small cohort of mostly ruxolitinib pre-treated patients, SI and treosulfan-based conditioning appeared a safe and effective tool to reduce spleen dimensions and ameliorate symptoms. Future prospective studies with adequate sample size are warranted to further investigate the usefulness and safety of this approach in MF.

Bacterial Bloodstream Infections after Allogeneic Hematopoietic Stem Cell Transplantation: Etiology, Risk Factors and Outcome in a Single-Center Study

Background—Allogeneic hematopoietic stem cell transplant (allo-HSCT) recipients are subject to major risks for bacterial bloodstream infections (BSIs), including emergent multidrug-resistant (MDR) organisms, which still represent the main cause of morbidity and mortality in transplanted patients. Methods: We performed an observational, retrospective, single-center study on patients undergoing allo-HSCT between 2004 and 2020 at the Stem Cell Transplant Unit in Turin to assess the incidence, etiology, and outcomes of BSIs and to explore any risk factors for bacteriaemia. Results: We observed a total of 178 bacterial BSIs in our cohort of 563 patients, resulting in a cumulative incidence of 19.4%, 23.8%, and 28.7% at 30, 100, and 365 days, respectively. Among isolated bacteria, 50.6% were Gram positive (GPB), 41.6% were Gram negative (GNB), and 7.9% were polymicrobial infections. Moreover, BSI occurrence significantly influenced 1-year overall survival. High and very high Disease Risk Index (DRI), an haploidentical donor, and antibacterial prophylaxis were found as results as independent risk factors for bacterial BSI occurrence in multivariate analysis. Conclusions: In our experience, GNB have overwhelmed GPB, and fluoroquinolone prophylaxis has contributed to the emergence of MDR pathogens. Local resistance patterns and patients’ characteristics should therefore be considered for better management of bacteremia in patients receiving an allogeneic HSCT.

Busulfan or Treosulfan Conditioning Platform for Allogeneic Stem Cell Transplantation in Patients Aged >60 Y With Acute Myeloid Leukemia/Myelodysplastic Syndrome: A Subanalysis of the GITMO AlloEld Study

The conditioning regimens with different alkylators at different doses can influence the outcome of allogeneic stem cell transplantation (SCT), but conclusive data are missing.

Methods

With the aim to analyze real-life allogeneic SCTs performed in Italy between 2006 and 2017 in elderly patients (aged >60 y) with acute myeloid leukemia or myelodysplastic syndrome, we collected 780 first transplants data. For analysis purposes, patients were grouped according to the type of alkylator included in the conditioning (busulfan [BU]-based; n = 618; 79%; treosulfan [TREO]-based; n=162; 21%).

Results

No significant differences were observed in nonrelapse mortality, cumulative incidence of relapse, and overall survival, although in the TREO-based group, we observed a greater proportion of elderly patients (P < 0.001); more active diseases at the time of SCT (P < 0.001); a higher prevalence of patients with either hematopoietic cell transplantation-comorbidity index ≥3 (P < 0.001) or a good Karnofsky performance status (P = 0.025); increased use of peripheral blood stem cells as graft sources (P < 0.001); and greater use of reduced intensity conditioning regimens (P = 0.013) and of haploidentical donors (P < 0.001). Moreover, the 2-y cumulative incidence of relapse with myeloablative doses of BU was significantly lower than that registered with reduced intensity conditioning (21% versus 31%; P = 0.0003). This was not observed in the TREO-based group.

Conclusions

Despite a higher number of risk factors in the TREO group, no significant differences were observed in nonrelapse mortality, cumulative incidence of relapse, and overall survival according to the type of alkylator, suggesting that TREO has no advantage over BU in terms of efficacy and toxicity in acute myeloid leukemia and myelodysplastic syndrome.

Identifying the optimal conditioning intensity for stem cell transplantation in patients with myelodysplastic syndrome: a machine learning analysis

A conditioning regimen is an essential prerequisite of allogeneic hematopoietic stem cell transplantation for patients with myelodysplastic syndrome (MDS). However, the optimal conditioning intensity for a patient may be difficult to establish. This study aimed to identify optimal conditioning intensity (reduced-intensity conditioning regimen [RIC] or myeloablative conditioning regimen [MAC]) for patients with MDS. Overall, 2567 patients with MDS who received their first HCT between 2009 and 2019 were retrospectively analyzed. They were divided into a training cohort and a validation cohort. Using a machine learning-based model, we developed a benefit score for RIC in the training cohort. The validation cohort was divided into a high-score and a low-score group, based on the median benefit score. The endpoint was progression-free survival (PFS). The benefit score for RIC was developed from nine baseline variables in the training cohort. In the validation cohort, the hazard ratios of the PFS in the RIC group compared to the MAC group were 0.65 (95% confidence interval [CI]: 0.48-0.90, P = 0.009) in the high-score group and 1.36 (95% CI: 1.06-1.75, P = 0.017) in the low-score group (P for interaction < 0.001). Machine-learning-based scoring can be useful for the identification of optimal conditioning regimens for patients with MDS.

Intensified conditioning regimens improved disease-free survival and engraftment after unrelated single-unit cord blood transplantation but not after matched sibling or matched unrelated donor allogeneic hematopoietic cell transplantation

The impact of conditioning intensity on different donor groups has been unclear in allogeneic transplantation. The objective of this study was to clarify the effect of conditioning intensity on disease-free survival (DFS), relapse, non-relapse mortality (NRM), neutrophil engraftment, and graft-versus-host disease for each donor type. We retrospectively evaluated the effect of conditioning intensity on transplant outcomes for patients with acute leukemia or myelodysplastic syndrome aged between 16 and 60 years in Japan using the transplant conditioning intensity (TCI) scoring system. A total of 8526 patients who received first allogeneic transplantation from 6/6 antigen-matched sibling donor (MSD, n = 2768), 8/8 allele-matched unrelated donor (MUD, n = 2357), and unrelated single-cord blood (UCB, n = 3401) were eligible for the analyses. Compared to conditioning with TCI score 4.0, which was corresponds to conventional myeloablative conditioning, including cyclophosphamide with total body irradiation 12 Gy or busulfan 12.8 mg, and was considered as the reference group in the multivariate analyses, intensified conditioning with TCI score ≥4.5 improved DFS (hazard ratio [HR],0.81, P < 0.001) and relapse rate (HR, 0.70, P < 0.001) but only after UCB transplants and not MSD and MUD transplants. In contrast, NRM was higher after intensified conditioning with TCI score ≥4.5 for MSD (HR, 1.39, P = 0.008) and MUD (HR, 1.47, P = 0.002) transplants but not UCB transplants (HR, 1.12, P = 0.240). Neutrophil engraftment was also significantly higher after intensified conditioning with TCI score ≥4.5 but only for UCB transplants (HR, 1.24, P < 0.001), whereas it was significantly lower after reduced-intensity conditioning with TCI score ≤3.5 for MSD transplants only (HR, 0.82, P < 0.001). These data demonstrated that an intensified conditioning regimen improved survival and engraftment rate only after a UCB transplants. Therefore, TCI scoring system could enable the optimization of conditioning intensity according to donor type, particularly in terms of survival and engraftment.

Outcomes after allogeneic haematopoietic stem cell transplantation in young adults in Germany

Young adults (YA) represent a minority among recipients of allogeneic haematopoietic stem cell transplantation (HSCT). In order to describe the outcome of YA following HSCT in Germany, 9299 patients who were registered with the German Registry for Stem Cell Transplantation were included in this retrospective analysis of the years 1998-2019. The impact of the variables, such as patient age and sex, sex differences, stem cell source, donor type, conditioning, year of HSCT, the diagnosis, and the achieved remission status were tested in univariable and multivariable analysis for overall, event-free and relapse-free survival as well as for the cumulative incidences of non-relapse and therapy-related mortality. Altogether, the outcome of YA after HSCT improved over time and was determined by the underlying disease, the age at disease onset, stem cell source, and donor type. Patients were most likely to die from relapse, and survival of HSCT recipients after 10 years was reduced by more than half in comparison to the general population of YA. Deeper understanding of modifiable risk factors may be gained by studies comparing the outcome of YA post-HSCT with that of children, adolescents and elderly patients. A deliberate and strong patient selection may further improve mortality rates.

High Molecular and Cytogenetic Risk in Myelofibrosis Does Not Benefit From Higher Intensity Conditioning Before Hematopoietic Cell Transplantation: An International Collaborative Analysis

There is no direct evidence to recommend specific conditioning intensities in myelofibrosis undergoing allogeneic hematopoietic cell transplantation, especially in the molecular era. We aimed to compare outcomes of reduced intensity (RIC) or myeloablative conditioning (MAC) transplantation in myelofibrosis with molecular information. The study included 645 genetically annotated patients (with at least driver mutation status available), of whom 414 received RIC and 231 patients received MAC. The median follow-up time from transplantation was 6.0 years for RIC and 9.4 years for MAC. The 6-year overall survival rates for RIC and MAC were 63% (95% confidence interval [CI], 58%-68%) and 59% (95% CI, 52%-66%; P = 0.34) and progression-free survival was 52% (95% CI, 47%-57%) and 52% (95% CI, 45%-59%; P = 0.64). The 2-year cumulative incidence of nonrelapse mortality was 26% (95% CI, 21%-31%) for RIC and 29% (95% CI, 23%-34%) for MAC (P = 0.51). In terms of progression/relapse, the 2-year cumulative incidence was 10% (95% CI, 5%-19%) for RIC and 9% (95% CI, 4%-14%) for MAC (P = 0.46). Higher intensity conditioning did not seem to improve outcomes for higher-risk disease, according to mutational, cytogenetic, and clinical profile. In contrast, patients with reduced performance status, matched unrelated donors, and ASXL1 mutations appeared to benefit from RIC in terms of overall survival.

Reduced intensity versus non-myeloablative conditioning regimen for haploidentical transplantation and post-transplantation cyclophosphamide in complete remission acute myeloid leukemia: a study from the ALWP of the EBMT

The optimal conditioning regimen prior haploidentical stem cell transplantation (Haplo-SCT) with post transplantation cyclophosphamide (PT-Cy) for acute myeloid leukemia (AML) remains unknown. A non-myeloablative conditioning (NMAC) regimen (cyclophosphamide + fludarabine + TBI 2 Gy [CyFluTBI]) is a safe approach, but relapse incidence remains high in this setting. Alternatively, a reduced intensity conditioning (RIC) regimen combining thiotepa and reduced-dose busulfan with fludarabine (TBF) may decrease AML relapse. However, an excess of toxicity may counterbalance this potential benefit. We retrospectively compared CyFluTBI vs. TBF in CR AML patients who underwent Haplo-SCT with PT-Cy, in two different populations based on age. We analyzed 490 patients. In patients aged <60 years (n = 203), we observed a higher RI (HR = 3.59, 95% CI = 1.75-7.37, p < 0.01), lower LFS (HR = 1.98, 95% CI = 1.22-3.22, p < 0.01) and lower OS (HR = 1.73, 95% CI = 1.04-2.88, p = 0.04) in the CyFluTBI group, without significant difference in NRM. In older patients (n = 287), we observed that conditioning regimen did not significantly influence LFS (HR = 0.90, 95% CI = 0.56-1.44, p = 0.65), OS (HR = 0.81, 95% CI = 0.49-1.32, p = 0.39) and RI (HR = 1.78, 95% CI = 0.90-3.50, p = 0.10), but showed that CyFluTBI was associated with a significantly lower risk of NRM (HR = 0.48, 95% CI = 0.25-0.92, p = 0.03). Thus, younger patients seem to benefit from conditioning intensification from CyFluTBI to TBF regimens prior PT-Cy Haplo-SCT for CR AML, while older ones do not.

Hematopoietic stem cell transplantation and cellular therapies for autoimmune diseases: overview and future considerations from the Autoimmune Diseases Working Party (ADWP) of the European Society for Blood and Marrow Transplantation (EBMT)

Autoimmune diseases (ADs) represent a heterogenous group of complex diseases with increasing incidence in Western countries and are a major cause of morbidity. Hematopoietic stem cell transplantation (HSCT) has evolved over the last 25 years as a specific treatment for patients with severe ADs, through eradication of the pathogenic immunologic memory and profound immune renewal. HSCT for ADs is recently facing a unique developmental phase across transplant centers. This review provides a comprehensive overview of the recent evidence and developments in the area, including fundamentals of preclinical research, clinical studies in neurologic, rheumatologic and gastroenterologic diseases, which represent major indications at present, along with evidence of HSCT for rarer indications. Moreover, we describe the interwoven challenges of delivering more advanced cellular therapies, exploiting mesenchymal stem cells, regulatory T cells and potentially CAR-T cell therapies, in patients affected by ADs. Overall, we discuss past and current indications, efficacy, associated risks and benefits, and future directions of HSCT and advanced cellular therapies in the treatment of severe/refractory ADs, integrating the available literature with European Society for Blood and Marrow Transplantation (EBMT) registry data.

Improving allogeneic stem cell transplantation in myelofibrosis

In this review, we will outline dimensions in which outcome of patients with myelofibrosis undergoing curative treatment can be optimized: patient selection, transplant procedure, and posttransplant prevention or treatment of relapse. For patient selection, fortunately, as with several other hematologic malignancies, the management of patients with myelofibrosis has very much entered the molecular era, with the establishment of several driver and nondriver mutations, allowing more individualized selection for treatment. For the transplant procedure itself, different conditioning intensities do not seem to play a distinctive role with regards to outcome posttransplant but still need to be compared in the molecular era. While many patients nowadays may receive ruxolitinib before transplant, recent studies may facilitate fine-tuning and integration of ruxolitinib into the transplant algorithm. The role of novel inhibitors for the transplant setting remains unclear. For the posttransplant phase, evidence remains scarce, with experiences of donor-lymphocyte infusions for relapse management but more efforts are needed in understanding relapse and identifying and treating patients at high risk for relapse.

Management of Invasive Fungal Infections in Patients Undergoing Allogeneic Hematopoietic Stem Cell Transplantation: The Turin Experience

Background

Allogeneic hematopoietic stem cell transplant (allo-HSCT) recipients are exposed to an increased risk of invasive fungal infections (IFIs) due to neutropenia, immunosuppressive treatments, graft-versus-host disease (GvHD) and incomplete immune reconstitution. Although clinical benefit from antifungal prophylaxis has been demonstrated, IFIs remain a leading cause of morbidity and mortality in these patients. In the last decades, attention has also been focused on potential risk factors for IFI to tailor an antifungal prevention strategy based on risk stratification.

Aim of the Study

This retrospective single-center study aimed to assess the epidemiology and the prognostic factors of IFI in a large cohort of allo-HSCT patients.

Methods

Between January 2004 and December 2020, 563 patients with hematological malignancies received an allo-HSCT at the Stem Cell Transplant Unit in Turin: 191 patients (34%) received grafts from a matched sibling donor, 284 (50.5%) from a matched unrelated donor, and 87 (15.5%) from an haploidentical family member. The graft source was peripheral blood in 81.5% of the patients. Our policy for antifungal prophylaxis included fluconazole in matched related and unrelated donors, while micafungin was administered in patients receiving haploidentical transplant. According to this practice, fluconazole was administered in 441 patients (79.6%) and micafungin in 62 (11.2%), while only 9 patients received mold-active prophylaxis. Galactomannan testing was routinely performed twice a week; patients with persisting fever unresponsive to broad spectrum antibiotics were evaluated with lung high-resolution computed tomography (HRCT) scan. In case of imaging suggestive of IFI, bronchoalveolar lavage (BAL) was performed whenever feasible.

Statistical Analysis

Only probable/proven IFI (PP-IFI) occurring during the first 12 months after transplant have been evaluated. IFIs were classified as probable or proven according to the new revised European Organization for Research and Treatment of Cancer (EORTC)/Mycoses Study Group (MSG) consensus criteria. Multivariate competing risk regression, binary logistic, and proportional hazard models were performed to identify risk factors for PP-IFI.

Results

A total of 58 PP-IFIs (n = 47 probable; n = 11 proven) occurred in our patients resulting in a cumulative incidence of 4.1%, 8.1%, and 9.6% at 30, 180, and 365 days, respectively. Molds were the predominant agents (n = 50 Aspergillus; n = 1 Mucor), followed by invasive candidemia (n = 5 non-albicans Candida; n = 1 Candida albicans; n = 1 Trichosporon). Lung was the most frequent site involved in patients with mold infections (47/51, 92.2%). Median time from HSCT to IFI was 98.44 days (0–365 days). Only 34.5% of patients with IFI were neutropenic at the time of infection. The presence of IFI had a significant impact on overall survival at 1 year (IFI, 32.8% vs. non-IFI, 54.6%; p < 0.001). IFI-related mortality rate was 20.7% in the overall population, 17% in patients with probable IFI, and 36% in patients with proven IFI. Multivariate competing risk regression revealed that donor type was the factor significantly associated to the risk of IFI [subdistribution hazard ratio (SDHR), 1.91, IC 1.13–3.20; p = 0.015]. BAL was informative in a consistent number of cases (36/57, 63.2%) leading to the identification of fungal (21), bacterial (4), viral (3), and polymicrobial (8) infections. Overall, 79 patients (14%) received a diagnostic-driven treatment, and 63 patients (11.2%) received a fever-driven treatment. Liposomal amphoteric B was the drug used in the majority of patients receiving diagnostic-driven therapy (30/79, 38%), while caspofungin was administered more frequently in patients who received a fever-driven strategy (27/63, 42.9%).

Conclusion

According to our experience, a non-mold active prophylaxis in patients undergoing allo-HSCT is feasible when combined with an intensive diagnostic work-up including CT scan and BAL. BAL performed at the onset of the disease may provide informative results in most patients. A diagnostic-driven treatment strategy may contribute to limit the use of costly antifungal therapies.

Reduced intensity hematopoietic stem cell transplantation for myelofibrosis in accelerated-phase

Results of this first report in accelerated-phase myelofibrosis may encourage clinicians to refer these patients for curative treatment.

Accelerated-phase myelofibrosis without prior cytoreduction showed excellent 5-year survival (65%) but higher relapse vs chronic phase.

Accelerated-phase myelofibrosis, currently defined by circulating blasts 10% to 19%, usually confers very high risk for progression and poor outcome. The outcome of hematopoietic stem cell transplantation for accelerated-phase myelofibrosis has not been evaluated yet. We analyzed the outcome of 349 clinically and genetically annotated patients with primary or secondary myelofibrosis undergoing reduced intensity transplantation, of whom 35 had accelerated-phase myelofibrosis. In comparison with chronic-phase (<10% blasts) myelofibrosis, median leukocyte counts were higher, more patients had constitutional symptoms, and RAS mutations were detected more frequently in the accelerated-phase group. After a median follow-up of 5.9 years, estimated 5-year overall survival was 65% (95% confidence interval [CI], 49% to 81%) vs 64% (95% CI, 59% to 69%) for the chronic-phase group (P = .91), and median overall survival was not reached. In terms of relapse-free survival, estimated 5-year outcome for the accelerated-phase group was 49% (95% CI, 32% to 67%) vs 55% (95% CI, 50% to 61%) for the chronic-phase group (P = .65). Estimated 5-year nonrelapse mortality was 20% (95% CI, 8% to 33%) for the accelerated-phase group vs 30% (95% CI, 24% to 35%; P = .25) for the chronic-phase group. In terms of relapse, 5-year incidence was 30% (95% CI, 14% to 46%) for the accelerated-phase group vs 15% (95% CI, 11% to 19%) for the chronic-phase group (P = .02). Results were confirmed in multivariable analysis and propensity score matching. In conclusion, reduced intensity transplantation showed excellent survival but higher relapse for accelerated-phase myelofibrosis.

Treosulfan-Based Conditioning Regimen Prior to Allogeneic Stem Cell Transplantation: Long-Term Results From a Phase 2 Clinical Trial

Introduction

Reducing toxicities while preserving efficacy in allogeneic stem cell transplant (allo-HCT) remains a particularly challenging problem. Different strategies to enhance the antitumor activity without increasing early and late adverse toxicities of the conditioning regimens have been investigated.

Methods

The aim of “AlloTreo” prospective phase 2 clinical trial was to evaluate the efficacy and safety of a conditioning regimen based on Treosulfan (42 g/m²) and fludarabine (https://clinicaltrials.gov/ct2/show/NCT00598624). We enrolled 108 patients with hematological diseases who received a first allo-HCT between June 2005 and January 2011, inside the frame of this trial at our center. Median age at allo-HCT was 49 (21–69) years. Disease Risk Index was low in 14 (13%) patients, intermediate in 73 (67.7%), high in 17 (15.7%), and very high in 4 (3.7%). Donors were human leukocyte antigen (HLA)-matched related in 50 cases, 10/10-matched unrelated in 36, and 9/10-mismatched unrelated in 22. Graft-versus-host disease (GvHD) prophylaxis consisted of cyclosporine-A and methotrexate. Anti-T-lymphocyte globulin (ATLG) was administered in patients receiving unrelated allo-HCT. Stem cell source was mainly peripheral blood stem cells (95%).

Results

Conditioning regimen was well tolerated. Full donor chimerism was documented for most patients (88%) at day +30. At 12 years, overall survival (OS) was 41.7% (32.2%–50.9%), progression-free survival (PFS) was 31.7% (23%–40.7%), GvHD-free/relapse-free survival was 20.9% (13.7%–29.1%), cumulative incidence (CI) of relapse was 44.5% (34.9%–53.6%), and transplant-related mortality (TRM) was 22.5% (15.1%–30.9%). CI of acute GvHD grades II–IV was 27.8% (19.7%–36.5%) at 100 days; 12-year CI of chronic GvHD was 40.7% (31.3%–49.9%). Relevant long-term adverse effects were 10 secondary malignancy, 3 fatal cardiovascular events, and 1 late-onset transplant-associated thrombotic microangiopathy. Ten successful pregnancies were reported after allo-HCT. In multivariate analysis, older age (≥60 years) at transplant [hazard ratio (HR), 2.157; p = 0.004] and a high/very high disease risk index (HR, 1.913; p = 0.026) were significantly associated with a lower OS.

Conclusions

Overall, our data confirmed the myeloablative potential and safe toxicity profile of full dose Treo (42 g/m²) especially for the younger population.