Introduction: Monitoring of chimeric antigen receptor (CAR) transgene levels in peripheral blood post tisagenlecleucel (tisa-cel) infusion provides information on expansion and persistence of CAR T-cells. In adult diffuse large B cell lymphoma (DLBCL) and follicular lymphoma (FL) patients (pts), the expansion of CAR T-cells was similar between responding and non-responding pts, while in pediatric and young adult acute lymphoblastic leukemia (ALL) pts, higher expansion in responding pts was observed. Based on long term follow up data from tisa-cel treated pts, analyses were performed to delineate the impact of CAR persistence and B cell aplasia on duration of remission (DOR). Methods: Transgene levels in blood measured by quantitative polymerase chain reaction were available from pivotal phase II studies in pts with r/r ALL (ELIANA [N=79], ENSIGN [N=64], NCT03123939 [N=69], NCT01626495 [N=60]), r/r DLBCL (JULIET [N=115]), and r/r FL (ELARA [N=97]), along with the long term follow up study (NCT02445222). The time related to loss of persistence of CAR T-cells (T loss) was defined as the time at which transgene levels first dropped below 50 transgene copies/µg DNA (approximates to lower limit of quantification (LLOQ) of the assay) after maximal expansion. Kaplan Meier analysis was performed to investigate the impact of duration of T loss and time corresponding to last quantifiable level (T last) on DOR/relapse. The impact of time to B cell recovery (>1% CD19+ B cells/WBCs or >3% CD19+ B cells/lymphocytes for ALL, and 80-616 cells/µL for DLBCL and FL), on DOR/relapse was also investigated. Results: Long term CAR persistence in tisa-cel treated pts has been observed for up to 9, 6, and 2.5 years for ALL, DLBCL, and FL pts, respectively, reflecting differing length of follow up based on initiation of trials in respective indications. Across indications, pts who lost transgene within 6 months or between 6-12 months had shorter DOR relative to pts with persistent transgene (Fig 1, ALL pts). In ALL, the median T loss was 27.4, 18.2, 9.7, and 18.0 months for ongoing complete response (CR) > 12 months, CR pts between 6-12 months, relapsed pts < 12 months, and relapsed pts > 12 months, respectively. However, of the pts who lost transgene within first 6 months, some pts maintained durable responses for ≥12 months (29%, 15%, and 50% in ALL, DLBCL, and FL, respectively). Among ALL relapsed pts, majority (17/26, 65%) of the pts with T loss < 6 months showed B cell recovery, however 6 pts had T loss at < 6 months as well as B-cell recovery but maintained response for ≥ 12 months. In ALL, Pulsipher et al.,(Blood Cancer Discov. 2022)have shown that NGS MRD within the first 6 months to 1 year post infusion may be a more reliable predictor of potential relapse than B cell recovery. The median time to B-cell recovery was 266 days in pts who relapsed/censored within 12 months but was not reached for pts with ongoing response at 12 months. On the contrary, B cell recovery seems to have no association with relapse in DLBCL or FL pts. Of the ALL pts with CAR persistence, pts with <50% morphologic blasts at any time prior to infusion of tisa-cel had longer DOR compared to pts with ≥50% blasts. This may also reflect a more resistant high risk ALL at the time of study entry or greater potential for stochastic loss of CD19 in pts with the higher disease burden. Conclusions: Long term sustained remission/response was observed in tisa-cel treated pts in the pivotal trials. The analyses demonstrate a positive association between CAR persistence and durable clinical responses across indications, however, some pts maintained durable responses despite early loss of transgene and/or early B cell recovery (< 6 months post infusion; Myers et al., J Clin Oncol. 2021). To note, in DLBCL and FL, the transgene levels in blood may not represent the levels at target sites including lymph nodes, moreover, T last and T loss are dependent on the duration of follow up, LLOQ etc. Of note, these analyses represent data from pivotal tisa-cel clinical studies with a heavily treated pt population post multiple lines of therapy including prior HSCT, and may not represent pts treated with commercial product, at earlier times post diagnosis in current studies with fewer lines of prior treatment, lower pre-infusion disease burden, and/or other CAR product. In pts with early loss of transgene, further research is needed to identify potential factors or patient characteristics resulting in durable responses.

Objectives: Studies to date of MRD detection pre-/post-HCT in children with ALL include insufficient numbers for multivariate analyses and lack comparison of methodologies (flow cytometry (FC) vs. RQ-PCR). To address these issues, the Westhafen Intercontinental Group (WIG) assembled an international database. Patients and Methods: Patients were treated in Europe, North America and Australia and transplanted between 09/99 and 05/16. 747 pts were included from whom 2960 bone marrow MRD measurements were performed. MRD was assessed prior to HCT and on or near days +30, +60, +100, +180, +365 and beyond after HCT. Pts were in CR1 (n = 275), CR2 (n = 410), >CR3 (n=53), or non-remission (NR) (n=7). 586 pts had pre-B ALL, 145 had T-cell ALL and 16 had bi-lineage or bi-phenotypic AL. Grafts were sibling (MSD; n=227), unrelated (MUD; n=314), mismatched (MMD, n=75), or cord blood (n=128). 31 pts were <2y/o, 365 were ≥2 and ≤ 10, and 351 were >10 at HCT. Pts were placed in 3 groups for analysis according to MRD level: 1) no detectable MRD, 2) MRD <10E-4 (.01% by FC) “MRD low positive”, and MRD ≥10E-4 “MRD high positive”. A second analysis compared those tested by FC (n = 272 pre- and 775 post-HCT) with those tested by RQ-PCR (381 pre- and 1532 post-HCT). Results: Pre-HCT MRD was available in 648 pts. MRD high, low and negative, patients showed a 4 yr-pEFS of 37%, 67%, and 62% (P < .0005). Pts with a high pre-HCT MRD had a 2.47 fold increased HR for relapse and a 1.67 increased risk of TRM (P < .0005). Cox Regression analysis showed that pre-HCT MRD and remission status both significantly influenced survival. Age, sex, relapse site, cytogenetics, donor type, and stem cell source did not influence outcome. MRD values post-HCT were analysed as time-dependent covariates. 4y-pEFS at day +30 for MRD high, MRD low and MRD negative pts were: 43%, 65%, and 59%, respectively (P = .002); at day +60 36%, 47%, and 64%, respectively (P < .008); at day +90 44%, 69%, and 65%, respectively (P < .003); at day +180 12%, 40%, and 79%, respectively; and at day +365 25%, 36%, and 87%, respectively. High MRD at all time points post-HCT led to higher relapse and TRM. At all pre- and post-HCT time points both FC and RQ-PCR levels ≥10-4 were highly predictive of relapse. At pre- and post-HCT points where adequate numbers were available for comparison, RQ-PCR values ≥ 10-4 ≤ 10-3 better predicted outcomes compared to FC (e.g. pre-HCT FC HR 1.26, RQ-PCR 2.41; d+30 FC HR 1.33, RQ-PCR 2.53; day +365 FC HR 3.54, RQ-PCR 31.84, all points P < .05). Summary and Conclusion: This large study confirmed that MRD pre- and post-HCT is a powerful predictor for survival. These results suggest MRD measurement pre-/post-HCT could be used to guide post-HCT interventions. Of note, RQ-PCR resulted in better predictive sensitivity at low MRD states compared to FC, however, a direct comparison of both approaches on the same patient cohort would be needed to validate this finding.

Transfusion practices for bone marrow harvests: a survey analysis from the AABB Bone Marrow Quality Improvement Initiative Working Group

CTL019 is an investigational anti-CD19 chimeric antigen receptor (CAR) T-cell therapy that reprograms cytotoxic T cells to eliminate target cells. A single-center trial demonstrated high response rates and a manageable safety profile in pediatric/young adult patients with R/R B-ALL. We report an updated analysis from the first multicenter, global, pivotal registration trial of CAR T-cell therapy (ELIANA; NCT02435849).

A total of 21 patients with severe aplastic anemia (SAA) underwent marrow transplantation from HLA-identical siblings following a standard conditioning regimen with cyclophosphamide (50 mg/kg/day × 4 days) and horse antithymocyte globulin (30 mg/kg/day × 3 days). Post-grafting immunosuppression consisted of a short course of methotrexate (MTX) combined with cyclosporine (CSP). The transplant protocol tested the hypothesis that the incidence of chronic GvHD could be reduced by limiting the marrow grafts to ⩽2.5 × 108 nucleated marrow cells/kg. None of the patients rejected the graft, all had sustained engraftment and all are surviving at a median of 4 (range 1–8) years after transplantation. Chronic GvHD developed in 16% of patients given ⩽2.5 × 108 nucleated marrow cells/kg. Post-grafting immunosuppression has been discontinued in 20 of the 21 patients. In conclusion, limiting the number of transplanted marrow cells may have resulted in minimal improvement in the incidence and severity of chronic GvHD.

We previously showed that minimal residual disease (MRD) detection pre-hematopoietic cell transplant (HCT) and acute GvHD (aGvHD) independently predicted risk of relapse in pediatric ALL. In this study we further define risk by assessing timing of relapse and the effects of leukemia risk category and post-HCT MRD. By multivariate analysis, pre-HCT MRD <0.1% and aGvHD by day +55 were associated with decreased relapse and improved event-free survival (EFS). Intermediate leukemia risk status predicted decreased relapse, and improved EFS and overall survival (OS). Patients with pre-HCT MRD ⩾0.1% who did not develop aGvHD compared with those with MRD <0.1% who did develop aGvHD had much worse survival (2 years EFS 18% vs 71%; P=0.001, 2 years OS 46 vs 74%; P=0.04). Patients with pre-HCT MRD <0.1% who did not experience aGvHD had higher rates of relapse than those who did develop aGvHD (40% vs 13%; P= 0.008). Post-HCT MRD led to a substantial increase in relapse risk (HR=4.5, P<0.01). Patients at high risk of relapse can be defined after transplant using leukemia risk category, presence of MRD pre or post HCT, and occurrence of aGvHD. An optimal window to initiate intervention to prevent relapse occurs between day +55 and +200 after HCT.

In 2007 the WMDA responded to the publication of two manuscripts suggesting a causal link between G-CSF and myeloid malignancies in healthy donors by convening an international symposium to examine this issue. At the time, registries reviewed the long-term follow-up of their healthy donors, which suggested no excess of leukaemia in PBSC donors compared with BM donors. Although the evidence for an increased risk of malignancy in healthy donors was felt to be weak, it could not be excluded. The WMDA, therefore, issued a statement, to be included in all donor consent forms, stating that it was unknown whether G-CSF increased or decreased the risk of later developing cancer. In 2012, with 5 years of additional donor follow-up and the results of several genetic studies now available, the clinical working group of the WMDA again reviewed the data. On the basis of an assessment of a continuing lack of evidence for an increased risk of malignancy in donors receiving G-CSF, the WMDA has re-issued a more reassuring statement. The revised statement was circulated to all WMDA member registries in late 2012 to replace the existing statement in consent forms, which now conclusively states that, 'Studies following large numbers of unrelated donors have shown that the risk of developing cancer within several years after the use of G-CSF is not increased compared with donors not receiving G-CSF'. Herein we review the evidence on which this statement is based.

Recent investigations have found a higher incidence of adverse events associated with hematopoietic cell donation in related donors (RDs) who have morbidities that if present in an unrelated donor (UD) would preclude donation. In the UD setting, regulatory standards ensure independent assessment of donors, one of several crucial measures to safeguard donor health and safety. A survey conducted by the Center for International Blood and Marrow Transplant Research (CIBMTR) Donor Health and Safety Working Committee in 2007 reported a potential conflict of interest in >70% of US centers, where physicians had simultaneous responsibility for RDs and their recipients. Consequently, several international organizations have endeavored to improve practice through regulations and consensus recommendations. We hypothesized that the changes in the 2012 Foundation for the Accreditation of Cellular Therapy and the Joint Accreditation Committee-International Society for Cellular Therapy and European Society for Blood and Marrow Transplantation standards resulting from the CIBMTR study would have significantly impacted practice. Accordingly, we conducted a follow-up survey of US transplantation centers to assess practice changes since 2007, and to investigate additional areas where RD care was predicted to differ from UD care. A total of 73 centers (53%), performing 79% of RD transplantations in the United States, responded. Significant improvements were observed since the earlier survey; 62% centers now ensure separation of RD and recipient care (P < .0001). This study identifies several areas where RD management does not meet international donor care standards, however. Particular concerns include counseling and assessment of donors before HLA typing, with 61% centers first disclosing donor HLA results to an individual other than the donor, the use of unlicensed mobilization agents, and the absence of long-term donor follow-up. Recommendations for improvement are made.

The inaugural meeting of 'New Frontiers in Pediatric Allogeneic Stem Cell Transplantation' organized by the Pediatric Blood and Transplant Consortium (PBMTC) was held at the American Society of Pediatric Hematology and Oncology Annual Meeting. This meeting provided an international platform for physicians and investigators active in the research and utilization of pediatric Allo-SCT in children and adolescents with malignant and non-malignant disease (NMD), to share information and develop future collaborative strategies. The primary objectives of the conference included: (1) to present advances in Allo-SCT in pediatric ALL and novel pre and post-transplant immunotherapy; (2) to highlight new strategies in alternative allogeneic stem cell donor sources for children and adolescents with non-malignant hematological disorders; (3) to discuss timing of immune reconstitution after Allo-SCT and methods of facilitating more rapid recovery of immunity; (4) to identify strategies of utilizing Allo-SCT in pediatric myeloproliferative disorders; (5) to develop diagnostic and therapeutic approaches to hematological complications post pediatric Allo-SCT; (6) to enhance the understanding of new novel cellular therapeutic approaches to pediatric malignant and non-malignant hematological disorders; and (7) to discuss optimizing drug therapy in pediatric recipients of Allo-SCT. This paper will provide a brief overview of the conference.

Although most children with ALL can be cured by chemotherapy approaches, allogeneic hematopoietic cell transplant (HCT) therapy offers a better chance of cure to selected high-risk patients in first remission and most children who relapse. Although transplant-related mortality has decreased significantly in the past decade, relapse remains high after HCT for ALL; developing strategies to decrease relapse and improve survival are vital. Recent studies have shown that relapse risk can be accurately defined using measurements of minimal residual disease ( MRD) both pre- and post-HCT and by knowing whether patients get GVHD in the first 2 months after transplant. With these risk definitions in hand, investigators are now applying novel agents and immunotherapeutic methods in attempt to lower MRD before transplant and modulate the GVL effect after transplant. With powerful new immunological approaches coming on line, the transplant process itself will likely expand to include pre and/or post-HCT interventions aimed at reducing relapse.

The number of patients receiving a BMT is currently being used as a factor in the accreditation process in determining whether a center can provide a high-quality BMT. Such criteria particularly impact pediatric BMT centers as most of them perform a relatively small number of BMTs. To determine whether patient volume is a valid marker of pediatric BMT center’s capabilities, the Pediatric Blood and Marrow Transplant Consortium (PBMTC) evaluated data from its registry to define the relationship between a pediatric transplant center’s patient volume and day +100 mortality. The analyses evaluated 2575 transplants from 60 centers reporting to the PBMTC between the years 2002 and 2004. The volume–outcome relationship was evaluated while adjusting for 46 independent data categories divided between nine variables that were known- or suspected-mortality risk factors. We found no association between transplant center volume and day +100 mortality in several analyses. A calculated intraclass correlation coefficient also indicated that differences in individual transplant center volume contributed to only 1% of the variance in day +100 mortality within the PBMTC. The results of this study suggest that factors other than transplant center volume contribute to variation in day +100 mortality among pediatric patients.

The National Marrow Donor Program (NMDP) projects the need for allogeneic unrelated blood and marrow transplants (BMT) in the United States is 10,000 per year. While the NMDP is preparing to facilitate that number by 2015, there are a number of barriers to meeting this need including recruiting additional health care personnel including BMT providers. To learn how best to recruit BMT physicians, we sought to understand why practicing BMT physicians chose to enter BMT, and why others did not. We conducted a web-based survey amongst Pediatric Hematology/Oncology (PHO) and BMT physician providers and trainees to determine the factors influencing their decision to choose or not choose a career in BMT. There were 259 respondents (48% male, 74% of Caucasian origin); 94 identified as BMT physicians, 112 as PHO physicians and 53 as PHO trainees. PHO and BMT providers spent an average of 53% in clinical activities. More than 2/3 of PHO providers stated that they provide BMT services at their institutions, most commonly inpatient coverage (73%). The proportion of providers exposed to BMT early in their training was significantly higher amongst BMT providers than PHO providers (51% vs. 18% during medical school [p<0.0001] and 70% vs. 50% during residency [p < 0.005]). Exposure during fellowship (94%) did not differ amongst groups. The decision to pursue a career in BMT was made before fellowship (medical school or residency) in 50% of the respondents. A lower proportion of BMT providers reported currently being involved in education of medical students and residents compared to PHO providers (98% vs. 76%, p<0.0001). Of 53 trainees, 64% reported that they were not contemplating a career in BMT. Of these, 68% stated that inadequate exposure to BMT prior to PHO fellowship was the reason. Only 26% reported BMT exposure in medical school and 43% during residency. The two most common reasons for the choice of a BMT career were the degree of intellectual and scientific challenge (89%) and role models/mentors in the field (67%). This survey suggests that early exposure to BMT during medical school and residency results in increased interest in pursuing a career in BMT. BMT physicians and training program directors can foster interest in the BMT field by promoting BMT focused education and clinical inpatient and outpatient rotations during medical school and residency. This early exposure to BMT may aid in a higher recruitment of future transplant providers.