Intravenous Busulfan-Based Myeloablative Conditioning Regimens Prior to Hematopoietic Cell Transplantation for Hematologic Malignancies

Busulfan Once Versus Four Times Daily: Impact on Pharmacokinetics, Organ Toxicities and Survival After Allogeneic Hematopoietic Stem Cell Transplantation

Therapeutic drug monitoring of busulfan (Bu) used as conditioning for allogeneic stem cell transplantation (allo-HSCT) is recommended as pharmacokinetics (PK) display variability. Since 2019, we give Bu 1x/d (Bu-Q24) instead of 4x/d (Bu-Q6) for practical convenience, despite limited studies evaluating the best way of application. Our aim was to analyze the correlation between Bu administration (Bu-Q6 versus Bu-Q24), Bu-PK and clinical outcome in 256 adult patients receiving Bu as conditioning regimen for allo-HSCT. This is a retrospective study of adult patients receiving a myeloablative chemotherapeutic regimen containing Bu to treat hematological malignancies. The population was separated into 2 groups according to Bu administration, namely Bu-Q6 and Bu-Q24. A total of 133 patients received Bu-Q6 and 123 Bu-Q24. Bu-Q6 patients were more commonly treated with cyclophosphamide and Bu-Q24 with fludarabin. Bu-Q6 showed lower cumulative area-under-the-curve values than Bu-Q24 (63.78 mg/h/L in Bu-Q6 and 70.12 mg/h/L in Bu-Q24, P = .06). Only 44% of the patients fell within the 1st AUC FDA target range in Bu-Q6 versus 62% in Bu-Q24 (P < .01). Overall, Bu-Q24 appeared to be superior to Bu-Q6 for most outcomes, showing lower incidence of toxicity grade≥II (78% versus 90%, P = .02), with less uro-renal (14% in Bu-Q24 versus 26% in Bu-Q6; P = .02), pulmonary (2% versus 8%, P = .05) and gastro-intestinal toxicities (10% versus 17%, P < .01). Patient receiving Bu-Q24 had fewer infections (51% versus 65%; P = .04), particularly bacterial (33% versus 47%, P = .03) and fungal infections (10% versus 20%; P = .03). At 2 yr, Bu-Q24 tended to have lower treatment-related mortality (5% versus 10%, P = .13), relapse rate (37% versus 42%, P = .55) and incidence of acute and chronic graft-versus-host-disease (24% versus 28%; 32% versus 36%, respectively). The overall survival was 81% (95% CI 74% to 89%) in Bu-Q24 and 69% (95% CI 62% to 77%, P = .03) in Bu-Q6, without impact on the relapse rate or incidence of acute and chronic graft-versus-host-disease. The only benefit of Bu-Q6 was mucositis grade≥III, with an incidence of 36% versus 60% in Bu-Q24 (P < .01). At 2 yr, patients with a cumulative AUC < 59.11 mg/h/L had the lowest TRM, without impact on the OS. Bu clearance was largely influenced by BMI and age > 60 yr. Bu administered once a day shows benefit both in the short and long term compared to Bu administered 4 times a day, but data are heterogeneus, Bu-Q24 being more commonly associated with use of fludarabine, Bu-Q6 with use of cyclophosphamide in this study.

Fludarabine Plus Myeloablative Dose of Busulfan Regimen Was Associated with High Nonrelapse Mortality in Allogeneic Hematopoietic Stem Cell Transplantation for Malignant Lymphoma: A Propensity Score-Matched Comparison Study with Fludarabine Plus High-Dose Melphalan

In recent years, there have been notable advancements in the treatment of malignant lymphoma. However, a certain percentage of patients are unlikely to achieve a cure through chemotherapy alone. Therefore, allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains a crucial curative treatment for malignant lymphoma. FluBu4, comprising fludarabine (Flu) combined with a myeloablative dose of intravenous busulfan (Bu; 12.8 mg/kg in total), is a widely used conditioning regimen for allo-HSCT, but its usefulness in malignant lymphoma (ML) has not been fully investigated. The objective of this study was to evaluate the efficacy and safety of FluBu4 in allo-HSCT for lymphoma by comparing the outcomes of two conditioning regimens: FluBu4 and FluMel140. We used a Japanese national database from the Transplant Registry Unified Management Program to retrospectively analyze the first allo-HSCT for ML in patients aged ≥16 years. Allo-HSCT cases treated with posttransplant cyclophosphamide were excluded. Two groups, namely FluBu4 and FluMel140 were selected by propensity score matching (PSM) with a case ratio of 1:2. From 921 cases, 113 were selected by PSM for the FluBu4 group and 226 for the FluMel140 group. The median age was 54 (19 to 68) years, the median observation period of survivors was 33.8 months, and 145 (42.7%) had a history of autologous HSCT. There were no significant differences in patients' backgrounds between the two groups after PSM. Three-year overall survival (OS) was significantly worse for FluBu4 than for FluMel140 (28.0% versus 48.6%; P < .01). The 3-year cumulative relapse rate was comparable for FluBu4 and FluMel140 (40.1% versus 38.5%; P = .65). However, 3-year nonrelapse mortality was significantly higher for FluBu4 than for FluMel140 (35.3% versus 22.5%; P = .02). There was no significant difference between the two treatment groups in the cumulative incidence of acute graft-versus-host disease (aGVHD) at day 100 after allo-HSCT and the 3-year cumulative incidence of chronic GVHD. While the common and major cause of death was the relapse of lymphoma, aGVHD, and noninfectious lung complications were observed more frequently with FluBu4 than with FluMel140. One-year cumulative incidence of interstitial pneumonia was significantly higher for FluBu4 than for FluMel140 (5.3% versus 0.4%; P = .03). FluBu4 use was associated with worse nonrelapse mortality (NRM) and OS in allo-HSCT for ML compared with FluBu4 and FluMel140 adjusted by PSM. Patients treated with FluBu4 had a higher incidence of noninfectious pulmonary complications and an increased number of associated deaths. A higher rate of NRM in the patients treated with FluBu4 was particularly evident in patients aged ≥60, and its use should be avoided in this patient population.

A practical guide to therapeutic drug monitoring in busulfan: recommendations from the Pharmacist Committee of the European Society for Blood and Marrow Transplantation (EBMT)

Busulfan (Bu) is an important component of many conditioning regimens for allogeneic hematopoietic cell transplantation. The therapeutic window of Bu is well characterized, with strong associations between Bu exposure and the clinical outcome in adults (strongest evidence in myelo-ablative setting) and children (all settings). We provide an overview of the literature on Bu as well as a step-by-step guide to the implementation of Bu therapeutic drug monitoring (TDM). The guide covers the clinical, pharmacological, laboratory and administrative aspects of the procedure. Through this document, we aim to support centers in implementing TDM for Bu to further enhance the success rates of HCT and improve patient outcomes. The Pharmacist Committee of the European Society for Blood and Marrow Transplantation (EBMT) encourages all centers to perform TDM for Bu in the aforementioned indications.

The Effects of Busulfan on Xenogeneic Transplantation of Human Peripheral Blood Mononuclear Cells in Recipient Mice

BACKGROUND

Humanized mouse models with engraftment of human peripheral blood mononuclear cells (PBMCs) or hematopoietic stem cells (HSCs) are effective tools for the study of human immunity. Busulfan has been used as a substitute for irradiation in human hematopoietic stem cell (HSC) transplantation models, but it has not been tested in human peripheral blood mononuclear cell (PBMC) transplantation models.

METHODS

This study evaluated PBMC engraftment using cytometry and enzyme-linked immunosorbent assay (ELISA) in female NOD.CB17/Prkdcscid/JKrb/ IL2 receptor γ-/- (NIG) mice treated with busulfan.

RESULTS

In this model, the percentage of human CD3+ T cell engraftment in the blood was 28.2%, with dominant infiltration of CD8+ cells in the spleen 3 weeks post PBMC transplantation. Production of human cytokines, including Interleukin (IL)-12p70, IL-4, IL-5, IFN-γ, IL-6, IL-8, IL-22, Tumor Necrosis Factor alpha, and IL-10, was determined in mice treated with busulfan.

CONCLUSIONS

Our findings demonstrate that busulfan treatment is a beneficial alternative for simple and efficient PBMC engraftment in a rodent model, possibly helping to evaluate human immunity in preclinical studies.

Fludarabine/busulfan versus busulfan/cyclophosphamide as myeloablative conditioning for myelodysplastic syndrome: a propensity score-matched analysis

Myeloablative conditioning with fludarabine/busulfan (Flu/Bu4) prior to allogeneic hematopoietic stem cell transplantation (allo-HSCT) is effective for acute myeloid leukemia. However, the effectiveness of Flu/Bu4 for myelodysplastic syndrome (MDS) remains poorly understood. Therefore, we retrospectively analyzed nationwide registry data in Japan from 2006 to 2018 and compared transplant outcomes of adult MDS patients receiving Flu/Bu4 and busulfan/cyclophosphamide (Bu4/Cy) using propensity score (PS) matching. The primary endpoint was overall survival (OS). Among 2,482 MDS patients, 153 patients were assigned each to the Flu/Bu4 and Bu4/Cy groups. The 3-year OS rates were 52.7% (95% confidence interval [CI], 43.8-60.8%) and 49.5% (95% CI, 40.8-57.6%) in the Flu/Bu4 and Bu4/Cy group, respectively (P = 0.548). The 3-year progression-free survival (P = 0.858), the cumulative incidence of relapse (P = 0.536), and cumulative incidence of non-relapse mortality (P = 0.684) were not significantly different between the two groups. According to the findings of subgroup analyses, no patient had a favorable OS when using either of the two regimens. In conclusion, although our PS-matched cohort mainly comprised older patients who had a low hematopoietic cell transplantation-comorbidity index and low-risk disease status, Flu/Bu4 could be an alternative to Bu4/Cy for MDS patients prior to allo-HSCT.

Busulfan Pharmacokinetics in Adenosine Deaminase-Deficient Severe Combined Immunodeficiency Gene Therapy

The pharmacokinetics of low-dose busulfan (BU) were investigated as a nonmyeloablative conditioning regimen for autologous gene therapy (GT) in pediatric subjects with adenosine deaminase-deficient severe combined immunodeficiency disease (ADA SCID). In 3 successive clinical trials, which included either γ-retroviral (γ-RV) or lentiviral (LV) vectors, subjects were conditioned with BU using different dosing nomograms. The first cohort received BU doses based on body surface area (BSA), the second cohort received doses based on actual body weight (ABW), and in the third cohort, therapeutic drug monitoring (TDM) was used to target a specific area under the concentration-time curve (AUC). Neither BSA-based nor ABW-based dosing achieved a consistent cumulative BU AUC; in contrast, TDM-based dosing led to more consistent AUC. BU clearance increased as subject age increased from birth to 18 months. However, weight and age alone were insufficient to accurately predict the dose that would consistently achieve a target AUC. Furthermore, various clinical, laboratory, and genetic factors (eg, genotypes for glutathione-S-transferase isozymes known to participate in BU metabolism) were analyzed, but no single finding predicted subjects with rapid versus slow clearance. Analysis of BU AUC and the postengraftment vector copy number (VCN) in granulocytes, a surrogate marker of the level of engrafted gene-modified hematopoietic stem and progenitor cells (HSPCs), demonstrated gene marking at levels sufficient for therapeutic benefit in the subjects who had achieved the target BU AUC. Although many factors determine the ultimate engraftment following GT, this work demonstrates that the BU AUC correlated with the eventual level of engrafted gene-modified HSPCs within a vector group (γ-RV versus LV), with significantly higher levels of granulocyte VCN in the recipients of LV-modified grafts compared to recipients of γ-RV-transduced grafts. Taken together, these findings provide insight into low-dose BU pharmacokinetics in the unique setting of autologous GT for ADA SCID, and these dosing principles may be applied to future GT trials using low-dose BU to open the bone marrow niche.

Costs and Outcomes with Once-Daily versus Every-6-Hour Intravenous Busulfan in Allogeneic Hematopoietic Cell Transplantation

The high cost of healthcare in the United States has not been consistently associated with improved health outcomes or quality of care, necessitating a focus on value-based care. We identified busulfan dosing frequency during allogeneic hematopoietic cell transplantation (HCT) conditioning as a potential target for optimization. To improve patient convenience and to decrease the cost of busulfan-based conditioning regimens, our institution changed busulfan dose frequency from every 6 hours (q6h) to once-daily (q24h). We compared costs and patient outcomes between these 2 dosing schedules. In June 2017, our institution transitioned from q6h to q24h busulfan dosing. We compared patients who received busulfan/cyclophosphamide conditioning regimens (BU/CY) for allogeneic HCT in the year before the dosing change (q6h cohort) and those who did so in the year after the dosing change (q24h cohort). The primary outcomes were differences in cost, day +90 mortality, and day +90 relapse. Between June 1, 2016, and June 1, 2018, 104 patients (median age 49 years; range, 20 to 63 years) received BU/CY before allogeneic HCT. Fifty-nine patients (57%) received q6h busulfan and 45 (43%) received q24h busulfan. There were fewer men in the q24h busulfan cohort compared with the q6h busulfan cohort (42% versus 64%; P = .024), but there were no other significant differences between the groups. There was an average annual cost savings of $19,990 per patient with q24h busulfan compared with q6h busulfan, and an annual busulfan cost savings of $899,550. There was a significantly lower day +90 mortality in the q24h busulfan cohort compared to the q6h busulfan cohort (0% versus 10%; P = .028). There were no significant differences in relapse at day +90 or in hospital length of stay. Our data indicate that i.v. busulfan dosing for allogeneic HCT conditioning is a target for improved value-based care. At our institution, patients who received q24h busulfan dosing had similar or superior outcomes compared with those receiving q6h dosing, with an average annual cost reduction of $19,990 per patient and an overall annual reduction in busulfan cost of approximately $900,000. These data support the adoption of q24h i.v. busulfan dosing as a standard of care to improve value-based care in allogeneic HCT.

Conditioning regimen with a 75% dose of standard busulfan/cyclophosphamide plus fludarabine before cord blood transplantation in older patients with AML and MDS

In this retrospective study, we aimed to establish a conditioning regimen for older patients receiving cord blood transplantation (CBT). This study included 21 older patients [median age 65 (58-73) years] with acute myeloid leukemia and myelodysplastic syndrome who underwent single CBT following a conditioning regimen comprising fludarabine (FLU) 125-175 mg/m², busulfan (BU) 9.6 mg/kg, and cyclophosphamide (CY) 90 mg/kg. Twelve patients (57.1%) were considered high or very high risk according to the disease risk index. Nineteen achieved neutrophil engraftment at a median of 19 days (range 14-29 days) after CBT (cumulative incidence 90.5%). During a median observation period of 24.3 months, the overall survival (OS) rates at 100 days and 2 years were 76.2% and 47.6%, respectively, with cumulative 2-year relapse and non-relapse mortality (NRM) rates of 19.0% and 38.1%, respectively. Infectious disease was the leading cause of NRM (n = 5) and occurred within 100 day post-transplantation in two patients. This suggested that the administration of a reduced BU/CY plus FLU regimen to older patients receiving CBT enables an early recovery with high neutrophil engraftment, relapse suppression, and acceptable NRM rates.

Safety and Efficacy of Once-Daily Intravenous Busulfan in Allogeneic Transplantation: A Matched-Pair Analysis

Compared with 4-times-daily infusion of intravenous busulfan (ivBU4), the safety and efficacy of once-daily infusion of ivBU (ivBU1) has not been fully clarified. We have been routinely using ivBU1 in a conditioning regimen in adult patients with myeloid malignancy who undergo allogeneic hematopoietic stem cell transplantation. In this study, a total of 91 patients who received ivBU1 for 2 days (n = 18) or 4 days (n = 73) in our institutions were compared with 273 control patients who received ivBU4, who were matched for age, sex, performance status, disease risk, conditioning regimen, and donor type, selected from the database of the Japanese Society for Hematopoietic Cell Transplantation using optimal matching algorithms. One-year overall survival (56.8% versus 57.1%, P = .94), disease-free survival (51.6% versus 50.8%, P = .73), relapse rate (28.5% versus 26.2%, P = .94), nonrelapse mortality (19.9% versus 23.0%, P = .71), and the incidence of graft-versus-host disease were not significantly different between the ivBU1 and ivBU4 groups. In patients who received ivBU1, neutrophil recovery was slower (median days: 22 versus 17, P = .001), and the incidence of veno-occlusive disease was lower (2.6% versus 17.4%, P = .04). In conclusion, ivBU1 can be safely administered with clinical outcomes similar to those with ivBU4.

A new intensive conditioning regimen for allogeneic hematopoietic stem cell transplantation in patients with refractory or relapsed acute myeloid leukemia

To explore the efficacy, and safety of the intensive conditioning regimen consisting of cladribine, cytarabine (Ara-C), and granulocyte colony-stimulating factor (G-CSF) plus modified busulfan (Bu) combined with cytoxan (Cy) (BuCy), prior to allogeneic hematopoietic stem cell transplantation (allo-HSCT) in patients with refractory, or relapsed acute myeloid leukemia (R/R AML).Thirty-Six R/R AML patients scheduled to receive allo-HSCT were consecutively, enrolled in this prospective study, and treated using intensive conditioning regimen consisting of CLAG plus modified BuCy. Median follow-up duration was 11.25 (range 0.5 - 21.0) months and the last follow up date was August 15, 2017.All patients (100%) achieved white blood cell (WBC) recovery within a median time of 16.00 (13.25 - 18.00) days, and 34 of them (94%) attained platelet (PLT) recovery within a median time of 13.50 (9.25 - 19.75) days. Incidence of acute graft-versus-host disease (aGVHD) was 50.00%, with median time of 71.50 (41.00 - 401.25) days. Three patients developed Grade I; nine, Grade II; 5, Grade III; and 1, Grade IV aGVHD. The incidence of chronic GVHD (cGVHD) was 44.40%, with median time of 255.00 (120.00 - 390.00) days. Four patients developed limited cGVHD, and 12, extensive cGVHD. One-year accumulating leukemia free survival (LFS), and overall survival (OS) rates between 52.9 ± 8.8% to 69.4 ± 7.7%, respectively. Eighteen (50%) patients were infected with cytomegalovirus; 2 (5.6%), with Epstein-Barr virus (EBV), 7 (19.4%), with hemorrhagic cystitis; 13 (36.1%), with bacteria; and 8 (22.2%), with fungus.Intensive conditioning regimen of CLAG plus modified BuCy for allo-HSCT may be effective and well-tolerated in R/R AML patients.

The confused oncologic patient: a rational clinical approach

PURPOSE OF REVIEW

The purpose of this review is to provide a practical clinical approach to confusion in the patient with cancer. Confusion in the cancer population has a broader differential diagnosis than in the general medical population. The clinician must consider the usual differential diagnoses as well as causes unique to the cancer patient including direct complications from the cancer and indirect complications related to cancer treatment.

RECENT FINDINGS

In the recent age of precision medicine, the oncologist now utilizes the genomic profile of both the patient and the tumor to provide advanced biologic therapies including targeted anticancer drugs, antiangiogenic agents, and immunotherapy. Such advances carry with them an emerging pattern of neurotoxicity which, although less well described in the literature, is now an important consideration to the clinical approach to confusion in cancer patients.

SUMMARY

Confusion is the most common neurologic complication in cancer and is associated with significant morbidity, mortality, and prolonged hospital stays resulting in increased healthcare costs. Early recognition and treatment of delirium is essential to improve clinical outcomes.

Chimerism in Myeloid Malignancies following Stem Cell Transplantation Using FluBu4 with and without Busulfan Pharmacokinetics versus BuCy

In the era of precision medicine, the impact of personalized dosing of busulfan is not clear. We undertook a retrospective analysis of 78 patients with myeloid malignancies who received fludarabine and busulfan (FluBu4) with or without measuring Bu pharmacokinetics (Bu PK) and those who received busulfan with cyclophosphamide (BuCy). Fifty-five patients received FluBu4, of whom 21 had Bu PK measured, and 23 patients received BuCy. Total donor cell chimerism showed that the percentage of patients maintaining 100% donor chimerism on day 100 was 66.7%, 38.2%, and 73.9% in the FluBu4 with PK, FluBu4 with no PK, and BuCy, respectively (P = .001). Patients who had decreasing donor chimerism by day 100 were 23.8%, 52.9%, and 26.1% in the FluBu4 with PK, FluBu4 with no PK, and BuCy, respectively (P = .04). Bu PK group had fewer patients with less than 95% donor chimerism on day 30, which was not statistically significant, 5% (FluBu4 PK), 31% (FluBu4 with no PK), and 21% (BuCy) (P = .18). Survival distributions were not statistically significant (P = .11). Thus, personalized drug dosing can impact donor chimerism in myeloid malignancies. This will need to be examined in larger retrospective multicenter studies and prospective clinical trials.

Thiotepa-busulfan-fludarabine compared to busulfan-fludarabine for sibling and unrelated donor transplant in acute myeloid leukemia in first remission

Background

A preparatory regimen consisting of thiotepa-busulfan-fludarabine (TBF) has been associated with reduced relapse in patients with haematological malignancies after haploidentical and cord blood transplants; however, few data exist regarding TBF conditioning in sibling (MSD) and unrelated donor (URD) transplants for AML.

Results

Among patients receiving a myeloablative (MAC) regimen, TBF-MAC was associated with significantly lower relapse (HR 0.47, p = 0.005) however higher non-relapse mortality (NRM, HR 2.69, p < 10^–4) as compared to BF. This led to similar leukemia-free (LFS) and overall survival (OS) between the two regimens (LFS: p = 0.6; OS: p = 0.27). When we selected TBF-MAC patients receiving busulfan 9.6 mg/kg, NRM resulted still higher but no more significantly different as compared to BF-MAC with busulfan 12.8 mg/kg (HR 1.53, p = 0.12); despite the lower busulfan dose, relapse remained inferior with TBF-MAC (HR 0.45, p = 0.01), however no difference in survival could be demonstrated (LFS: p = 0.31; OS: 0.82). Among patients receiving a reduced-intensity (RIC) regimen, similar outcome was observed with TBF-RIC and BF-RIC (LFS: p = 0.77; OS: p = 0.88).

Conclusions

TBF-MAC as conditioning regimen for transplant from MSD and URD in AML patients in first remission provided stronger anti-leukemic activity but higher NRM as compared to BF-MAC, thus leading to similar survival. TBF-MAC with busulfan 9.6 mg/kg was associated with low relapse and acceptable NRM, however again with no survival benefit. TBF-RIC and BF-RIC resulted in comparable outcome.

Methods

We conducted a registry-based study comparing outcomes of patients with AML in first remission undergoing transplant from MSD or URD prepared with either TBF (n = 212) or BF (n = 2698) conditioning.

HLA haploidentical hematopoietic cell transplantation using clofarabine and busulfan for refractory pediatric hematological malignancy

Haploidentical hematopoietic cell transplantation (HCT) conditioning with clofarabine and target area under the blood concentration-time curve (AUC)-based busulfan adjustment was performed in three patients with refractory pediatric leukemia. The target AUC for two patients who had already received multiple transplantations was 3600 and 4000 μmol min/L, and that for the patient with Down's syndrome was 3000 μmol min/L. Regimen-related toxicity was well tolerated in all cases. All three maintained cytological remission throughout the follow-up period (between 31 and 167 weeks). Thus, haploidentical HCT conditioning with clofarabine and target AUC-based busulfan adjustment may be a preferable option for children with recurrent or refractory pediatric leukemia.

Personalizing Busulfan-Based Conditioning: Considerations from the American Society for Blood and Marrow Transplantation Practice Guidelines Committee

The Practice Guidelines Committee of the American Society of Blood or Marrow Transplantation (ASBMT) sought to develop an evidence-based review about personalizing busulfan-based conditioning. The Committee sought to grade the relevant published studies (June 1, 2008 through March 31, 2016) according to criteria set forth by the Steering Committee for Evidence Based Reviews from ASBMT. Unfortunately, the published literature was too heterogeneous and lacked adequately powered and sufficiently controlled studies for this to be feasible. Despite this observation, the continued interest in this topic led the Practice Guidelines Committee to develop a list of most frequently asked questions (FAQs) regarding personalized busulfan dosing. This "Considerations" document is a list of these FAQs and their responses, addressing topics of practical relevance to hematopoietic cell transplantation clinicians.