Conditioning Stem Cell Transplantation Research Articles

The impact of age and renal function on the pharmacokinetics and protein binding characteristics of fludarabine in paediatric and adult patients undergoing allogeneic haematopoietic stem cell transplantation conditioning.

To evaluate the population pharmacokinetics of unbound F-Ara-A (the circulating metabolite of fludarabine) in 211 patients (age range, 0.1-63.4years) undergoing allogeneic haematopoietic stem cell transplantation conditioning. Total (n = 2480) and unbound (n = 1403) F-Ara-A concentrations were measured in blood samples collected at timed intervals after fludarabine doses ranging from 10 to 50mg/m2 and infused over 0.42-1.5h. A three-compartment population pharmacokinetic model was developed based on unbound plasma concentrations and used to estimate F-Ara-A unbound pharmacokinetic parameters and fraction unbound (fu). A number of covariates, including glomerular filtration rate (GFR) and post-menstrual age (PMA), were evaluated for inclusion in the model. The base population mean estimates ± relative standard error (%RSE) for unbound clearance from the central compartment (CLu) and inter-compartmental clearances (Q2u, Q3u) were 3.42 ± 3%, 6.54 ± 24% and 1.47 ± 16% L/h/70kg, respectively. The population mean estimates (%RSE) for the unbound volume of distribution into the central (V1u) and peripheral compartments (V2u, V3u) were 9.65 ± 8%, 8.17 ± 9% and 16.4 ± 10% L/70kg, respectively, and that for fu was 0.877 ± 1%. Covariate model development involved differentiating F-Ara-A CLu into non-renal (1.81 ± 9% L/h/70kg) and renal components (1.02 ± 9%*GFR L/h/70kg). A sigmoidal maturation factor was applied to renal CLu, with population mean estimates for the Hill exponent and PMA at 50% mature of 2.97 ± 4% and 69.1 ± 8%weeks, respectively. Patient age and GFR are predictors of unbound F-Ara-A CLu. This has the potential to impact dose requirements. Dose individualisation by target concentration intervention will be facilitated by this model once it is externally validated.

A Comparative Analysis of Low Dose Grafalon® Versus Thymoglobuline® as Serotherapy in Hematopoietic Stem Cell Transplant in Pediatric and Young Adult Population

Anti-thymocyte globulin (ATG) forms an essential component of conditioning in hematopoietic stem cell transplantation (HSCT). Due to the shift of donor preference to alternate donors, reliance on rabbit-ATG (rATG) has increased. Two different forms of rATG (Thymoglobuline® and Grafalon®) are available for clinical use but data to support the use of one over the other is sparse. We retrospectively analyzed data of 144 patients who underwent allogenic-HSCT for benign hematological conditions at our center, from August 2019 to August 2023. Of these, 87 received Grafalon® and 57 received Thymoglobuline®. The majority (77.7%) underwent HSCT for hemoglobinopathies and all received pre-transplant immunosuppression. Engraftment kinetics was similar in 2 cohorts. Six patients had primary graft failure (PGF). There was no difference in the incidence of PGF stratified by serotherapy. Overall survival(OS) for the cohort was 74.9%. Kaplan–Meier estimate of OSand EFSwas significantly better in Grafalon® group than Thymoglobuline® (84.4 ± 0.04% vs 64.1% ±0.065%) (p-value= 0.04%) and (84.4 ± 0.04% and 61.2%±0.065% (p-value = 0.01)). Extensive chronic GVHD was (14%) higher in Thymoglobuline® group and (2.3%) in Grafalon®. Immune reconstitution at day + 100 was not statistically different between the two groups. On univariate analysis, Thymoglobuline® serotherapy (OR (95% CI) =4.665 (1.2–18.04))was associated with increased risk of acute grade III–IV GvHD. In our study, Grafalon® tended to have better OS, decreased incidence of acute grade III–IV GvHD, and extensive cGVHD. There was no difference in engraftment kinetics, PGF, and immune reconstitution between 2 cohorts of serotherapy.

Outcomes of melphalan 140mg/m2 followed by autologous stem cell transplantation in multiple myeloma patients with co-morbidities: Single-centre experience.

High-dose melphalan followed by stem cell rescue is the standard consolidative therapy for transplant-eligible patients with multiple myeloma (MM) in the United Kingdom. A melphalan dose of 200mg/m2 (Mel200) is considered the "gold standard" for autologous stem cell transplant (ASCT) conditioning for fit patients ≤70 years old; however, with a peak diagnosis incidence at 80-89 years old in the UK dose adjustments will be inevitable to limit toxicities. In this single-centre UK-based retrospective analysis, data was collected from patients with plasma cell dyscrasias who underwent a first reduced-intensity, Mel140, ASCT from 2006 to 2019, a total of 81 patients. We found that the procedure was overall safe with seven (9%) of patients requiring ITU admission and a single transplant-related death within the initial autograft admission. The progression-free survival (PFS) and overall survival were comparable with those previously reported in the literature with median PFS for our cohort of 31 months. Univariate analysis of our data showed an inferior PFS for patients aged ≥70 years. In conclusion, although this is a retrospective analysis, it demonstrates that dose-reduced melphalan conditioning is safe and effective in patients deemed unfit for standard-intensity conditioning.

Antiemetic prophylaxis regimens in haematologic malignancies patients undergoing a hematopoietic stem cell transplantation. Which is the best standard of care? A systematic review.

This systematic review, adhering to PRISMA guidelines, aimed to evaluate the efficacy and safety of antiemetic prophylaxis in haematological patients undergoing high-dose chemotherapy as part of their hematopoietic stem cell transplantation (HSCT) conditioning regimens. We performed a comprehensive search in PubMed, EMBASE, ClinicalTrials.gov and the Cochrane database to identify randomised controlled trials (RCTs) and systematic reviews of antiemetic prophylaxis. Studies in English, French, Italian or Spanish were included. This review is registered with PROSPERO, ID CRD42023406380. Eight RCTs were analysed. The antiemetic regimens evaluated ranged from monotherapy with 5-Hydroxytryptamine Receptor 3 antagonists (5-HT3RAs) to complex combinations including olanzapine, neurokinin-1 receptor antagonists, 5-HT3RAs and corticosteroids. Complete response rates for triplet or quadruple regimens varied between 23.5% and 81.9%. Although no significant adverse effects were observed, minor symptoms such as diarrhoea, constipation, sedation and headaches were reported. Existing evidence on HSCT antiemetic therapy highlights its benefits but fails to provide clear clinical directions. The choice between triplet and quadruplet therapies for different patient scenarios is still uncertain. Until more detailed research is available, healthcare providers must rely on the latest guidelines and their judgement to customise antiemetic care for each patient's specific needs and risks.

Cisplatin as a Viable and Secure Alternative to Carmustine in BEAM-Based Conditioning for Autologous Hematopoietic Stem Cell Transplantation in Patients with Lymphoma

BackgroundHigh-dose chemotherapy followed by autologous hematopoietic stem cell transplantation (auto-HSCT) is a standard treatment for relapsed/refractory lymphoma patients. Yet, the widespread use of BEAM is hindered by carmustine accessibility. This study evaluates the efficacy and safety of PEAM (Cisplatin, Etoposide, Cytarabine, and Melphalan) versus BEAM in auto-HSCT for Hodgkin (HL) and non-Hodgkin lymphoma (NHL) patients. MethodsWe conducted a retrospective single-center study of adult lymphoma patients who received PEAM or BEAM pretransplant conditioning between January 2004 to December 2022, comparing efficacy and safety outcomes. ResultsAmong 143 patients (median age of 33 years, 58% males), 55 had HL, and 88 had NHL. The overall response rate (ORR) was 86.7% for PEAM and 72.3% for BEAM, and the relapse rate (RR) was lower for PEAM than BEAM (22.9% vs 45.6%). Median time to relapse (TTR) and overall survival (OS) were not reached for either group. PEAM exhibited a shorter time to both neutrophil (NE) and platelet (PE) engraftment compared to BEAM (10 vs 12 days), with a more tolerable gastrointestinal (GI) toxicity profile. ConclusionsBoth BEAM and PEAM showed similar outcomes, demonstrating comparable efficacy in terms of ORR, TTR, and OS for both HL and NHL patients. However, PEAM-conditioning was associated with a shorter time to engraftment and fewer GI adverse events.

211At-Labeled Anti-CD45 Antibody as a Nonmyeloablative Conditioning for Canine DLA-Haploidentical Stem Cell Transplantation.

The α-emitter 211At deposits a high amount of energy within a few cell diameters, resulting in irreparable DNA double-strand breaks while minimizing off-target toxicity. We investigated the use of the 211At-labeled anti-CD45 monoclonal antibody (mAb) 211At-CD45-B10 as a nonmyeloablative conditioning regimen for dog-leukocyte-antigen-haploidentical hematopoietic cell transplantation. Methods: Seventeen healthy dogs were injected with either a 0.50 (n = 14) or 0.75 (n = 3) mg/kg dose of anti-CD45 mAb labeled with 211At (8.436-23.199 MBq [0.228-0.627 mCi/kg]) on day -3. Peripheral blood stem cells from dog-leukocyte-antigen-haploidentical donors were given on day 0. Peripheral blood chimerism was calculated by polymerase chain reaction assays, and blood clearance of the radioimmunoconjugate was studied using enzyme-linked immunosorbent assay and radioactivity measurements of serial blood samples. Results: All dogs achieved donor chimerism by day 28 (range, 27%-100%). The hematopoietic engraftment rate was 100%, though engraftment durability was variable. No difference in absorbed dose to blood was seen for the 2 mAb dosing levels studied. Neutropenia (0-29 cells/μL), lymphocytopenia (36-130 cells/μL), and thrombocytopenia (1.5-9 × 103/μL) with prompt recovery were observed. The main adverse nonhematologic event related to 211At-CD45-B10 was mild reversible transaminitis. Graft-versus-host disease was not seen. Twelve of the 17 dogs survived over 30 d, with donor chimerism ranging from 3% to 99%. Conclusion: The results suggest that nonmyeloablative conditioning with 211At-CD45-B10 could be used in haploidentical hematopoietic cell transplantation though with variable engraftment.

Extracellular release of damaged mitochondria induced by prehematopoietic stem cell transplant conditioning exacerbates GVHD

AbstractDespite therapeutic advancements, graft-versus-host disease (GVHD) is a major complication of hematopoietic stem cell transplantation (HSCT). In current models of GVHD, tissue injury induced by cytotoxic conditioning regimens, along with translocation of microbes expressing pathogen-associated molecular patterns, result in activation of host antigen-presenting cells (APCs) to stimulate alloreactive donor T lymphocytes. Recent studies have demonstrated that in many pathologic states, tissue injury results in the release of mitochondria from the cytoplasm to the extracellular space. We hypothesized that extracellular mitochondria, which are related to archaebacteria, could also trigger GVHD by stimulation of host APCs. We found that clinically relevant doses of radiation or busulfan induced extracellular release of mitochondria by various cell types, including cultured intestinal epithelial cells. Conditioning-mediated mitochondrial release was associated with mitochondrial damage and impaired quality control but did not affect the viability of the cells. Extracellular mitochondria directly stimulated host APCs to express higher levels of major histocompatibility complex II (MHC-II), costimulatory CD86, and proinflammatory cytokines, resulting in increased donor T-cell activation, and proliferation in mixed lymphocyte reactions. Analyses of plasma from both experimental mice and a cohort of children undergoing HSCT demonstrated that conditioning induced extracellular mitochondrial release in vivo. In mice undergoing MHC-mismatched HSCT, administration of purified syngeneic extracellular mitochondria increased host APC activation and exacerbated GVHD. Our data suggest that pre-HSCT conditioning results in extracellular release of damaged mitochondria, which increase alloreactivity and exacerbate GVHD. Therefore, decreasing the extracellular release of damaged mitochondria after conditioning could serve as a novel strategy for GVHD prevention.

Treosulfan- Versus Busulfan-based Conditioning in Allogeneic Hematopoietic Cell Transplantation for Myelodysplastic Syndrome: A Single-center Retrospective Propensity Score-matched Cohort Study

Treosulfan has shown promise in allogeneic hematopoietic cell transplantation (HCT) for its myeloablative properties and low toxicity. In this single-center retrospective propensity score-matched cohort study we compared treosulfan- and busulfan-based conditioning in allogeneic HCT for patients with myelodysplastic syndrome (MDS). This study included 138 adults who underwent allogeneic HCT for MDS or chronic myelomonocytic leukemia (CMML) at Princess Margaret Hospital, Toronto 2015-2022. Using propensity score matching, we compared transplant outcomes between two well-matched cohorts who received conditioning with either fludarabine-treosulfan (FT) (n=46) or fludarabine-busulfan with total body irradiation (FBT200) (n=92). A scoring system based on patient age, Karnofsky performance score and hematopoietic cell transplant comorbidity index was used to assign patients based on fitness to low-dose (30 g/m2) or high-dose (42 g/m2) treosulfan: 32 (69.6%) received high-dose treosulfan. The racial composition of the two groups was similar, with 27.2% and 21.7% of FBT200 and FT recipients, respectively, identifying as non-Caucasian (P=0.61). Primary outcomes were analyzed at a median follow-up of 747 days. Of all participants, 116 (84.0%) received graft-vs-host disease (GVHD) prophylaxis with post-transplant cyclophosphamide (PTCY) and anti-thymocyte globulin (ATG) . Patients who received FT had a superior 2-y overall survival (OS) compared to those who received FBT200: 66.9% (95% confidence interval (CI): 46.1-81.2) vs. 44.5% (95% CI: 34-54.4), hazards ratio (HR): 0.43, 95% CI: 0.22-0.84 (P=0.013). In multivariate analysis (MVA), only the use of fresh grafts (P=0.02) and FT (P=0.01) were associated with improved OS. FT was associated with superior 2-y relapse-free survival (RFS) compared to FBT200: 63.1% (95% CI: 42.6-77.9) vs. 39.1% (95% CI: 29.1-49.1), HR: 0.44 (95% CI: 0.24-0.81), P=0.008. In MVA, the use of fresh grafts (P=0.03) and FT (P=0.009) were associated with improved RFS. Recipients of FT demonstrated superior 2-y graft versus host disease relapse-free survival (GRFS) compared to those who received FBT200: 57.4% (95% CI: 37.8-72.8) vs. 35.1% (95% CI: 25.5-45). In MVA, only FT was associated with superior GRFS (P=0.02). FT recipients exhibited markedly superior 1-y event-free survival (EFS) compared to recipients of FBT200 in univariate analysis (40.3% (95% CI: 25.9-54.2) vs. 9.2% (95% CI: 4.4-16.3), HR: 0.47 (95%CI: 0.30-0.72), P<0.001) and MVA (P=0.004). FT was associated with lower 1-y non-relapse mortality (NRM) compared to FBT200 in univariate analysis (9.9% (95% CI: 3.0-21.8) vs. 29.7% (95% CI: 20.6-39.3), HR: 0.41 (95% CI: 0.17-0.96), P=0.04) and MVA (P=0.04). Our study utilized propensity score matching to demonstrate superiority of treosulfan- over busulfan-based conditioning in stem cell transplantation of patients with MDS and is the first to evaluate the performance of treosulfan-based conditioning in combination with ATG and PTCY. As such, it contributes to the increasing body of evidence supporting the safety of treosulfan, even at the dose of 42 g/m2.

Autologous hematopoietic stem cell transplantation conditioning regimens and chimeric antigen receptor T cell therapy in various diseases.

Conditioning regimens employed in autologous stem cell transplantation have been proven useful in various hematological disorders and underlying malig nancies; however, despite being efficacious in various instances, negative consequences have also been recorded. Multiple conditioning regimens were extracted from various literature searches from databases like PubMed, Google scholar, EMBASE, and Cochrane. Conditioning regimens for each disease were compared by using various end points such as overall survival (OS), progression free survival (PFS), and leukemia free survival (LFS). Variables were presented on graphs and analyzed to conclude a more efficacious conditioning regimen. In multiple myeloma, the most effective regimen was high dose melphalan (MEL) given at a dose of 200/mg/m2. The comparative results of acute myeloid leukemia were presented and the regimens that proved to be at an admirable position were busulfan (BU) + MEL regarding OS and BU + VP16 regarding LFS. In case of acute lymphoblastic leukemia (ALL), BU, fludarabine, and etoposide (BuFluVP) conferred good disease control not only with a paramount improvement in survival rate but also low risk of recurrence. However, for ALL, chimeric antigen receptor (CAR) T cell therapy was preferred in the context of better OS and LFS. With respect to Hodgkin's lymphoma, mitoxantrone (MITO)/MEL overtook carmustine, VP16, cytarabine, and MEL in view of PFS and vice versa regarding OS. Non-Hodgkin's lymphoma patients were administered MITO (60 mg/m2) and MEL (180 mg/m2) which showed promising results. Lastly, amyloidosis was considered, and the regimen that proved to be competent was MEL 200 (200 mg/m2). This review article demonstrates a comparison between various conditioning regimens employed in different diseases.

Phase 1 Study of Bortezomib, Fludarabine, and Melphalan, With or Without Total Marrow Irradiation, as Allogeneic Hematopoietic Stem Cell Transplant Conditioning for High-risk or Relapsed/Refractory Multiple Myeloma.

We conducted a phase 1 study of a conditioning regimen with or without total marrow irradiation (TMI) before allogeneic hematopoietic stem cell transplantation for patients with high-risk or refractory multiple myeloma. Eighteen patients were enrolled on one of 2 strata. Patients with no prior radiation received TMI (900 cGy), fludarabine (FLU), and melphalan (MEL) conditioning, with bortezomib added in the second cohort (stratum I). Patients with prior radiation received FLU, MEL, and bortezomib, without TMI (stratum II). Eight patients were enrolled in the TMI arm (stratum I). One of 3 patients in cohort 1 experienced dose-limiting toxicity (DLT), which led to the expansion to 3 more patients with no DLT. Cohort 2 enrolled only 2 patients due to low accrual, with bortezomib, added at 0.5 mg/m 2 ; neither experienced DLT. Nine patients were enrolled in the non-TMI arm (stratum II). Three patients were enrolled in cohort 1 (bortezomib 0.5 mg/m 2 ) and none experienced DLT. Three were enrolled in cohort 2 (bortezomib 0.7 mg/m 2 ), and 1 experienced DLT; therefore, the cohort expanded to 3 more patients. One more patient experienced DLT. Median overall survival on strata I and II was 44.5 months (95% CI: 1.73-not reached) and 21.6 months (95% CI: 4.1-72.7), respectively. Median progression-free survival on strata I and II was 18.1 months (95% CI: 1.73-not reached) and 8.9 months (95% CI: 2.7-24.4), respectively. TMI 900 cGy, FLU, and MEL are considered feasible as conditioning for allogeneic stem cell transplantation and may warrant further investigation due to favorable response rates and survival.

The paradigm of total body irradiation in acute lymphoblastic leukaemia: Therapeutic effectiveness versus the challenges of toxicity

IntroductionTotal body irradiation (TBI) is part of the myeloablative conditioning for hematopoietic stem cell transplantation (HSCT) in malignant hematologic disorders. This therapy has recently shown improved survival in acute lymphoblastic leukemia (ALL) compared to chemotherapy-based regimens. However, side effects are a significant limitation, especially in the pediatric population. Patients and methodsWe retrospectively analyzed the survival of patients with ALL who underwent an HSCT at a tertiary hospital between 1996 and 2009 (N = 69 HSCT in 57 patients). We differentiated a cohort that received TBI (N = 44) from another that did not (N = 25). Subsequently, we interviewed the survivors from the TBI group with a minimum of 10 years of follow-up (N = 18), asking about the presence of side effects. ResultsThe overall survival (OS) at 2 and 5 years was 79.1% and 65.2% respectively for the TBI group and 66.2% and 55.8% for the non-TBI group, although this difference was not significant (P=.31). The event-free survival (EFS) at 2 and 5 years was 77.3% and 63.6% respectively for the TBI group and 56% and 32% for the non-TBI group (P=.02). The probability of relapse (PR) at 2 years for those who received TBI was 10% compared to 28.6% for those who did not receive TBI (P=.005). Survivors who received TBI developed secondary neoplasms (39%), dyslipidemia (67%), cognitive impairments affecting memory (44%), recurrent respiratory infections (39%), thyroid abnormalities (45%), premature ovarian failure (89%), cataracts (22%), and psychological problems (44%). However, the quality of life, as self-assessed by the patients, was considered good for 83% of the participants.. ConclusionsPatients who received TBI had significantly higher EFS and lower PR. However, adverse effects are frequent and significant, although they do not subjectively affect quality of life.

Palonosetron in pediatric patients: A single-center, retrospective evaluation of policy and clinical practice guideline discordance.

Clinical practice guidelines (CPGs) recommending palonosetron for the prevention and management of chemotherapy-induced nausea and vomiting (CINV) were adapted for use at our institution. Palonosetron was restricted for use in patients experiencing breakthrough CINV and receiving highly emetogenic chemotherapy (HEC) or undergoing stem cell transplant conditioning and in patients with refractory CINV receiving HEC. Given the significant cost of palonosetron, we aimed to determine the proportion of chemotherapy blocks where palonosetron use was discordant with the institutional policy or source CPG. A retrospective review of the health records of patients who received palonosetron between 1 July 2019 and 30 June 2020 was undertaken. Details of palonosetron use, antiemetic regimen and the date and time of each vomit during the acute and delayed phases were collected for each chemotherapy block where palonosetron was given. Discordance with the institutional policy and the source CPG was determined by assessing the indication for palonosetron and the dose. In the subset of chemotherapy blocks where information regarding vomiting episodes was available, the extent of acute phase chemotherapy-induced vomiting (CIV) control was reported. Four hundred thirty-eight chemotherapy blocks, representing 122 patients (mean age 9 years), receiving 595 palonosetron doses were included. Palonosetron use was discordant with institutional policy during most (72%; 314/438) of the chemotherapy blocks analyzed. However, palonosetron use was concordant with the source CPG during most chemotherapy blocks (74%; 326/438). Complete CIV control during the acute phase was observed in 66% (195/295) of chemotherapy blocks where palonosetron was given, irrespective of concomitant antiemetics administered. The majority of palonosetron use at our institution was discordant with institutional policy, but concordant with the source CPG. Our institutional policy has since been updated to be more aligned with the source CPG.

In the era of Bortezomib-based Induction, intensification of Melphalan-based conditioning with Bortezomib does not improve Survival Outcomes in newly diagnosed Multiple Myeloma: a study from the Chronic Malignancies Working Party of the EBMT

Bortezomib (Vel)- Melphalan 200 mg/m2 (Mel200) (Vel-Mel) has been utilised to intensify conditioning in autologous hematopoietic stem cell transplantation (AHCT) for multiple myeloma (MM). This EBMT registry-based study compared Vel-Mel with Mel200 during upfront AHCT. Between 2010 and 2017, MM patients who received Vel-Mel (n = 292) conditioning were compared with 4,096 Mel200 patients in the same 58 centres. Pre-AHCT, compared to Mel200 patients, Vel-Mel patients had similar International Staging System (ISS) scores and cytogenetic risk profiles; a similar proportion had received bortezomib-based induction (85% and 87.3%, respectively) though they were younger with a better performance status. Vel-Mel patients were more likely to achieve CR post-induction (40.6% vs 20.3%, p < 0.001) and by day 100 of AHCT (CR/VGPR: 70.2 % vs. 57.2%, p < 0.001). There was no difference in 3-year PFS (49% vs 46%, p = 0.06) or early post-AHCT mortality. In multivariable analysis, Vel-Mel associated with inferior PFS (HR: 1.69 (1.27–2.25, p < 0.001) and OS (HR:1.46 (1.14–1.86,p = 0.002), similar to negative effects on PFS of advanced ISS (HR:1.56 (1.33–1.83, p < 0.001), high-risk cytogenetics (HR:1.43(1.18–1.74, p < 0.001) and poor post-induction response(<=PR)(HR: 1.43(1.25–1.62, p < 0.001) Overall, despite superior pre- and post-AHCT responses, there was no improvement in PFS or OS following Vel-Mel. This data supports the findings of the smaller prospective IFM study.

Efficacy of an antimicrobial stewardship intervention for early adaptation of antibiotic therapy in high-risk neutropenic patients

BackgroundThe 4th European Conference on Infections in Leukemia recommends early adaptation of empirical antibiotic therapy (EAT) for febrile neutropenia in stable patients.ObjectivesTo assess the efficacy of an antimicrobial stewardship (AMS) intervention promoting early de-escalation and discontinuation of EAT in high-risk neutropenic patients.MethodsThis before-after study was conducted in the hematology department of the University Hospital of Nice, France. The AMS intervention included the development of clinical decision support algorithms, a twice-weekly face-to-face review of all antibiotic prescriptions and monthly feedback on the intervention. The primary endpoint was overall antibiotic consumption during hospital stay, expressed as days of therapy (DOT).ResultsA total of 113 admissions were included: 56 during the pre-intervention period and 57 during the intervention period. Induction chemotherapy and conditioning for allogeneic stem cell transplantation were the most frequent reasons for admission. In the intervention period, there was a significant decrease in overall antibiotic consumption (median DOT 20 vs. 28 days, p = 0.006), carbapenem consumption (median DOT 5.5 vs. 9 days, p = 0.017) and anti-resistant Gram-positive agents consumption (median DOT 8 vs. 11.5 days, p = 0.017). We found no statistical difference in the rates of intensive care unit admission (9% in each period) and 30-day mortality (5% vs. 0%, p = 0.243). Compliance with de-escalation and discontinuation strategies was significantly higher in the intervention period (77% vs. 8%, p < 0.001).ConclusionA multifaceted AMS intervention led to high compliance with early de-escalation and discontinuation of EAT and lower overall antibiotic consumption, without negatively affecting clinical outcomes.

Impact of Time-to-Antibiotic Delivery in Pediatric Patients With Cancer Presenting With Febrile Neutropenia.

Febrile neutropenia (FN) in pediatric patients with cancer can cause severe infections, and prompt antibiotics are warranted. Extrapolated from other populations, a time-to-antibiotic (TTA) metric of <60 minutes after medical center presentation was established, with compliance data factoring into pediatric oncology program national rankings. All FN episodes occurring at Vanderbilt Children's Hospital (2007-February 2022) and a sample of episodes from Colorado Children's Hospital (2012-2019) were abstracted, capturing TTA and clinical outcomes including major complications (intensive care unit [ICU] admission, vasopressors, intubation, or infection-related mortality). Odds ratios (ORs) were adjusted for age, treatment center, absolute neutrophil count, hypotension presence, stem-cell transplant status, and central line type. A total of 2,349 episodes were identified from Vanderbilt (1,920) and Colorado (429). Only 0.6% (n = 14) episodes required immediate ICU management, with a median TTA of 28 minutes (IQR, 20-37). For the remaining patients, the median TTA was 56 minutes (IQR, 37-90), and 54.3% received antibiotics in <60 minutes. There were no significant associations between TTA (<60 or ≥60 minutes) and major complications (adjusted OR, 0.99 [95% CI, 0.62 to 1.59]; P = .98), and a TTA ≥60 minutes was not associated with any type of complication. Similarly, TTA, when evaluated as a continuous variable, was not associated with a major (OR, 0.99 [95% CI, 0.94 to 1.04]; P = .69) nor any other complication in adjusted analysis. There is no clear evidence that a reduced TTA improves clinical outcomes in pediatric oncology FN and thus it should not be used as a primary quality measure.

Determination of Busulfan and Melphalan in Plasma by Turbulent Flow Chromatography-Tandem Mass Spectrometry.

Melphalan and busulfan are DNA-alkylating agents that are often used concurrently in hematopoietic stem cell transplant (HCT) conditioning regimens. Studies have demonstrated that this combination of alkylating agents is very effective and well-tolerated prior to HCT. This combination is widely used for acute leukemia, advanced lymphoid malignancies, and multiple myeloma. Our goal was to develop an assay for the rapid measurement of both compounds simultaneously in the hopes that rapidly measuring their concentrations could possibly shorten the length of hospital stay. It would also simplify specimen handling in the clinic and the laboratory, reduce the amount of blood drawn, and allow for rapid reporting of the drug levels, thereby facilitating rapid dose adjustments.This chapter describes a validated method that measures both compounds simultaneously. Melphalan and busulfan were extracted from plasma with methanol containing deuterated internal standards. Turbulent flow chromatography coupled with reversed-phase HPLC was used for separation, while the mass spectrometer was set in the positive ion mode. This method has proven accurate and rapid and allowed for timely dose adjustments. The assay was linear over the clinically relevant ranges; the analytical measurement range for busulfan and melphalan was 10-5000ng/mLand 10-15,000 ng/mL, respectively. Specimens containing elevated drug levels were diluted yielding a final clinically reportable range of 10-25,000ng/mL for busulfan and 10-75,0000ng/mL for melphalan. This method is very suitable for simultaneous measurements of these drugs and is currently being used to support pharmacokineticstudies.

Increased Exceptional Response and Overall Survival Advantage for Patients with Multiple Myeloma Receiving Melphalan 200mg/m 2 Vs 140 Mg/m 2 Conditioning for Autologous Hematopoietic Stem Cell Transplantation

The standard conditioning regimen for multiple myeloma patients undergoing autologous hematopoietic stem cell transplant (HSCT) is intravenous melphalan dosed at 200mg/m 2 (mel200). Prior retrospective studies indicated that dose reduction to melphalan 140 mg/m 2 (mel140) confers similar progression-free (PFS) and overall survival (OS), leading to increased use of mel140 in patients with comorbidities or advanced age. A recent single-center retrospective study (Sharma et al, Leukemia Lymphoma 2023) identified an OS advantage yet similar PFS for mel200 vs mel140, suggesting that certain patient cohorts may benefit from mel200. These findings require confirmation and better understanding of the risks and benefits to different dosing strategies. We performed a single-center retrospective study of mel dosing and transplant outcomes at the University of Nebraska Medical Center between 2008-2018. Three hundred and sixty-two patients underwent a first autologous HSCT with mel conditioning; 95 received mel140 while 267 received mel200. Nearly all patients received maintenance therapy (n= 357, 99%). Patient demographic and disease factors were largely comparable between mel140 and mel200 cohorts including sex, response prior to HSCT (both 73% for very good partial response or better), and presence of high-risk cytogenetics (t(4;14), t(14;16), t(14;20), del17p; 15% vs 14%). The mel140 group was older (65.1 years vs 59.7 years), had higher hematopoietic cell transplantation-specific comorbidity index (HCT-CI) scores (64% vs 40% at ³3), and International Staging System (ISS) stages (40% vs 22% at stage III) than the mel200 group. Average creatinine clearance at transplant was 71 vs 91 mL/min/m 2 in the mel140 vs mel200 cohorts, respectively. OS favored mel200 with a median survival time of 94.4 vs 69.1 months (mel200 vs mel140, Figure 1, p = 0.002). There was no statistical difference in PFS between mel200 vs mel140 (median PFS 73.0 vs 60.5 months, p = 0.43, respectively). With Cox proportional hazards regression, we performed a multivariate analysis of risk factors on PFS and OS. For OS, age ( p = 0.02) retained statistical significance within the model. Mel dosing and high-risk cytogenetics (both p = 0.09) did not retain significance. HCT-CI may have an effect ( p = 0.04), but due to missing data on n= 125/362 subjects this could not be well evaluated. Response prior to HSCT, creatine clearance at transplant, and ISS stage were not statistically significant. Given the multiple variables assessed and missing data for HCT-CI we separately analyzed mel dosing together with the most significant variable in the model, age. In this subset OS model, mel200 was associated with an improved OS (hazard ratio (HR) 0.64, p = 0.03) while age was associated with an adverse effect (HR 1.11 per 5-year increase, p = 0.06). For the multivariate PFS model, only high-risk cytogenetics (HR 1.82 yes vs no, p = 0.004) retained statistical significance. Median engraftment was faster in mel200 cohort (67% vs 92% engraftment starting at ³D+12, p &amp;lt;0.001). We next examined the impact of mel dosing on the rate of exceptional response (Paquin et al, Blood Cancer Journal 2020), defined as alive and progression-free for 8 or more years. Twenty-nine of 362 patients (8%) met the requirements for exceptional response. Two (7%) received mel140 while 27 (93%) received mel200. Exceptional responders were younger and split evenly between male and female. The majority had at least a very good partial response prior to HSCT (79%). Only 2 exhibited high-risk cytogenetics; one received bortezomib and lenalidomide maintenance, the other only bortezomib. On multivariate analysis, only two factors contributed to exceptional response: mel dose (mel200 odds ratio (OR) 5.22, Table 1, p = 0.01) and HCT-CI (OR 0.66 for increasing score, Table 1, p = 0.02. High-risk cytogenetics was not associated with exceptional responders (OR 0.43 yes vs no, p = 0.38) which may be due to low sample size. We conclude that mel dosing impacts OS but not PFS in our cohort, though this effect is confounded by increasing age and potentially comorbidity. We report for the first time that mel200 dosing increases the rate of exceptional response compared to mel140. Overall, these data support recent conclusions by Sharma et al and challenge the previous reports of similar OS outcomes between mel200 and mel140 dosing.

Comparison of Myeloablative Conditioning with Cyclophosphamide and Total-Body Irradiation (Cy/TBI) Vs. Fludarabine, Melphalan, and Total-Body Irradiation (Flu/Mel/TBI) in Patients Undergoing Allogeneic Stem Cell Transplant for AML/ALL

Background: Cyclophosphamide combined with total-body irradiation (Cy/TBI) has been widely used worldwide as the standard myeloablative conditioning (MAC) for allogeneic stem cell transplantation (allo-HCT), but there are concerns about the antitumor effects of CY, as well as side effects, including cardiotoxicity and mucosal toxicity. A few studies suggest that the addition of an anticancer agent to a Cy/TBI regimen may reduce recurrence rates, but comparative studies of Cy/TBI regimens versus other TBI regimens are scarce. Furthermore, the recent expansion of post-transplant cyclophosphamide as graft-versus-host disease (GVHD) prophylaxis has increased its utility for cyclophosphamide-free conditioning regimens. Our institution has extensive experience with cord blood transplantation for relatively elderly patients with high-risk leukemia and has worked to develop safer and more effective MAC regimens other than Cy/TBI. The purpose of this study is to examine the safety and efficacy of fludarabine and melphalan combined with total-body irradiation (Flu/Mel/TBI) regimen, which is widely used at our institution, compared to Cy/TBI. Methods: We retrospectively analyzed adult acute leukemia patients who underwent allo-HCT between August 1994 to February 2023 at Toranomon Hospital. The inclusion criteria were as follows: a diagnosis of acute myeloid leukemia (AML) or acute lymphoblastic leukemia (ALL), the first allo-HCT, and Cy (120mg/kg) /TBI (8-12Gy) or Flu (180mg/m 2) /Mel (80-120mg/m 2) /TBI (8-12Gy) as MAC regimen. We excluded patients who underwent haploidentical transplantation with post-transplant cyclophosphamide. The primary endpoint was the 5-year cumulative incidence of relapse, and the secondary endpoints were the 5-year cumulative incidence of non-relapse mortality (NRM), 5-year overall survival (OS), and relapse-free survival (RFS). OS and RFS were estimated by the Kaplan-Meier method and multivariate Cox proportional hazard models. The cumulative incidence of relapse and NRM were investigated with a competing risk analysis using Gray's test and multivariable Fine and Gray competing risk regression. Results: A total of 198 patients were included in this study, comprising 101 patients treated with Cy/TBI and 97 treated with Flu/Mel/TBI. Patients who received Flu/Mel/TBI were of higher age (Median age: Cy/TBI 36 years vs. Flu/Mel/TBI 53 years, p&amp;lt;0.01), higher ECOG PS score (PS≥1: 51.5% vs. 66.0%, p=0.044), fewer AML (49.5% vs. 22.7%, p&amp;lt;0.01), and more frequent CBT (45.5% vs. 76.3%, p&amp;lt;0.01). Disease status at HCT (CR1: 53.5% vs. 43.3%, p=0.154) and HCT-CI scores (HCT-CI≥1: 35.6% vs. 44.3%, p=0.214) were not different between the two regimen groups. Regarding the primary endpoint, the 5-year cumulative incidence of relapse was significantly lower in Flu/Mel/TBI group (36.8% vs. 24.9%, p= 0.035). The cumulative incidence of NRM was not significantly different between the two groups (19.1% vs. 25.2%, p=0.345). In the multivariate analysis, conditioning with Flu/Mel/TBI was significantly associated only with a lower risk of relapse (HR: 2.817; 95%CI: 1.183-6.712; p=0.019). Regarding NRM, only disease status not in CR1 was associated with a higher risk (CR1 vs. non-CR1 HR: 2.21; 95%CI: 1.095-4.468; p=0.027). There was no significant difference in 5-year OS (Cy/TBI 48.1% vs. Flu/Mel/TBI 51.4%, p=0.604) and RFS (44.2% vs. 49.9%, p=0.24). Conclusion: Despite older age and worse PS in the Flu/Mel/TBI group, Flu/Mel/TBI had a significantly lower 5-year cumulative relapse rate than Cy/TBI, with no significant difference in NRM. Our results suggest that Flu/Mel/TBI is a reasonable alternative to CY/TBI and may be a superior TBI-containing MAC regimen.

A Conditioning Regimen of Bendamustine and Melphalan for Autologous Stem Cell Transplantation in Multiple Myeloma: A Phase 2, Single-Arm, Prospective Study

Aim: A registered study to investigate the efficacy and safety of bendamustine plus melphalan conditioning for autologous stem cell transplantation (ASCT) in multiple myeloma (MM) (ChiCTR2100047782). Method: Bendamustine and melphalan were given to patients at the dose of 150 mg/m 2 on Days -5 and -4 and 70 mg/m 2 on Days -3 and -2, respectively. Progression-free survival (PFS) and overall survival (OS) were used to assess the efficacy and adverse events were used to assess the safety of the conditioning regimen. Results: A total of 80 patients were included in our study. Of them, 45 patients achieved complete response (CR); 7 patients achieved very good partial response (VGPR), and 28 patients achieved partial response (PR) before ASCT. With a median follow-up period of 16 months, the overall PFS rate was 91%, and the overall OS rate was 95%. Patients with CR pre-transplantation were all in CR until the last follow-up; two patients with VGPR pre-transplantation relapsed and one of them died; four patients with PR pre-transplantation relapsed and one of them died. The median time to neutrophile and platelet engraftment were 11 (9-13) and 13 (10-18) days. Three patients experienced sepsis during ASCT. Vomiting occurred in 45 (57.2%) patients; diarrhea occurred in 27 (34.2%) patients, transaminase elevation was observed in 18 (22.3%) patients; mucositis was found in 16 (18.8%) patients. All these adverse events were grade 1-2, and no grade 3-4 adverse events were observed. Conclusion: Bendamustine plus melphalan regimen is promising for ASCT in MM patients, and the long-term efficacy and safety remain to be investigated.

Hematopoietic Stem Cell Transplantation (HCT) Conditioning Leads to NK Cell Cytotoxicity Limiting Endogenous Thymus Regeneration

The thymus is highly sensitive to acute injury such as the cytoreductive conditioning given pre-hematopoietic stem cell transplant (HCT). The thymus is capable of regeneration, however its reparative capacity and T cell productivity decline with age. This leaves HCT recipients vulnerable to relapse of malignancy and opportunistic infection - the leading causes of post-HCT mortality - during a prolonged period of lymphopenia. Better understanding the endogenous mechanisms by which thymus regeneration is regulated may inform therapeutic interventions to improve T cell reconstitution in these patients. Here, we report that HCT conditioning leads to rises in stimulatory cytokine IL-18, subsequent activation of NK cells and increased cytotoxicity, which aberrantly suppresses organ recovery. Our group has reported that HCT-conditioning by ionizing radiation leads to increased Caspase-1 mediated immunogenic cell death within the thymus (Kinsella 2023 BioRxiv). Consistent with the cleavage of Caspase-1, we found an increase in release of the inflammatory cytokines IL-1b and IL-18. Although mice deficient for IL-1b signaling receptor ( Il1r -/-) did not show any modulation in their ability to regenerate after TBI, we found that mice deficient for IL-18 signaling (Il18 -/-) exhibited increased thymic cellularity one week following acute damage by sublethal irradiation (SL-TBI) (Fig. 1A left). This led us to conclude that post-damage activation and release of IL-18 suppresses thymus regeneration. We found that IL-18R was not expressed on most developing thymocytes and although a minority of thymic epithelial cells expressed the receptor, mice with a deficiency in IL-18R restricted to TECs ( Il18r1fl/fl:Foxn1-Cre +) showed no difference in regenerative capacity following conditioning. To rule out an effect on hematopoietic progenitors, for which IL-18R expression has been reported ( Silberstein 2016 Cell Stem Cell 6;19), we performed a competitive transplantation of Il18r1 -/- and WT bone marrow and measured T cell production, which showed no competitive advantage of Il18r1 -/- donor cells; this demonstrated that IL-18 does not directly regulate progenitor cells themselves, but rather, more likely acts via a bystander thymus-resident population. Within the thymus, IL-18R was expressed by highly radioresistant NK1.1 + NKT and NK cells. Depletion of both populations with anti-NK1.1 monoclonal antibody improved thymus cellularity in WT mice (Fig. 1A middle). Notably, NKT deficient CD1d -/- mice showed no defective repair which suggested that the depletion upon NK1.1 + cell depletion is largely mediated by NK cells. Depletion of NK1.1 + cells in Il18 -/- mice did not improve regeneration further, suggesting that NK-mediated suppression is IL-18 dependent. Given the known role of IL-18 in NK cell activation, we hypothesized that the HCT-conditioning resultant rise in IL-18 stimulates NK cells leading to “accidental” targeting of regeneration promoting cells. NK cell production of cytotoxic factors including IFNg, GzmB and Perforin increases following radiation conditioning, although only mice deficient for Perforin and not IFNg -exhibited improved thymus cellularity 7 days post HCT-conditioning (Fig 1A right). Further supporting this hypothesis, IL-18R +CD49b + NK cells isolated from the thymus 2-days post-irradiation induced more target cell death in head-to-head cytotoxicity assays compared to NK cells isolated pre-radiation (Fig 1B). Finally, we observe TEC downregulation of NK cytotoxicity inhibitory ligand MHC-I following radiation conditioning, suggesting that critical regeneration promoting stroma may be the targets of these activated NK cells. These findings suggest that, while necessary for successful transplantation, conditioning regimens may induce cytotoxicity of bystander NK cells which suppresses thymus recovery. Furthermore, we implicate conditioning induced immunogenic cell death and increased IL-18 in the stimulation of these suppressive cytotoxic cells and suggest that therapeutically targeting IL-18 and NK cell cytotoxicity may improve T cell reconstitution post-HCT.