Fixed-dose administration and pharmacokinetically guided adjustment of busulfan dose for patients undergoing hematopoietic stem cell transplantation: a meta-analysis and cost-effectiveness analysis.

This study aims to evaluate the efficacy, safety, and long-term cost-effectiveness of fixed-dose busulfan (Bu) administration and pharmacokinetically (PK) guided adjustment of Bu dose for patients who underwent hematopoietic stem cell transplantation. The efficacy and safety of both dosing strategies were compared using a systematic review and meta-analysis. A Markov model was used in estimating relevant cost and health outcomes from the perspective of the health system. The primary outcomes of interest were lifetime cost, quality adjusted life-years (QALYs) gained, and incremental cost-effectiveness ratio (ICER) in dollar per QALY gained. Results showed that progression-free survival and overall survival in the PK-guided group were higher than that in the fixed-dose group, and the PK-guided group was associated with low non-relapse mortality and relapse rate. In contrast to safety, the incidence of acute graft-versus-host disease (GVHD) was the same in the two groups (P > 0.05). Cost-effectiveness analysis showed that the QALY of the PK-guided group (12.8135 QALYs and $582,475.07) increased by 2.0609 relative to that in the fixed-dose group (10.7526 QALYs and $562,833.20), and the ICER was $9530.72/QALY. One-way and probability sensitivity analyses confirmed the reliability of the results. In conclusion, the PK-guided approach has higher efficacy and is safer.

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.

Assessment of Chemotherapy-Induced Organ Damage with Ga-68 Labeled Duramycin.

PURPOSE: Evaluation of [68Ga]NODAGA-duramycin as a positron emission tomography (PET) tracer of cell death for whole-body detection of chemotherapy-induced organ toxicity. PROCEDURES: Tracer specificity of Ga-68 labeled NODAGA-duramycin was determined in vitro using competitive binding experiments. Organ uptake was analyzed in untreated and doxorubicin, busulfan, and cisplatin-treated mice 2 h after intravenous injection of [68Ga]NODAGA-duramycin. In vivo data were validated by immunohistology and blood parameters. RESULTS: In vitro experiments confirmed specific binding of [68Ga]NODAGA-duramycin. Organ toxicities were detected successfully using [68Ga]NODAGA-duramycin PET/X-ray computed tomography (CT) and confirmed by immunohistochemistry and blood parameter analysis. Organ toxicities in livers and kidneys showed similar trends in PET/CT and immunohistology. Busulfan and cisplatin-related organ toxicities in heart, liver, and lungs were detected earlier by PET/CT than by blood parameters and immunohistology. CONCLUSION: [68Ga]NODAGA-duramycin PET/CT was successfully applied to non-invasively detect chemotherapy-induced organ toxicity with high sensitivity in mice. It, therefore, represents a promising alternative to standard toxicological analyses with a high translational potential.

A Comprehensive Assessment of Toxicities in Patients with Central Nervous System Lymphoma Undergoing Autologous Stem Cell Transplantation Using Thiotepa, Busulfan, and Cyclophosphamide Conditioning.

High-dose therapy and autologous stem cell transplantation (ASCT) with thiotepa, busulfan, and cyclophosphamide (TBC) conditioning has emerged as an effective postinduction treatment strategy for patients with primary central nervous system lymphoma (PCNSL) or secondary central nervous system lymphoma (SCNSL), but it is associated with considerable toxicity and transplantation-related mortality (TRM) in the modern era. Forty-three adult patients with chemosensitive PCNSL or SCNSL underwent TBC-conditioned ASCT between 2006 and 2015. Twenty-eight of these patients received pharmacokinetically (PK)-targeted busulfan dosing. The median number of clinically relevant individual grade ≥3 nonhematologic toxicities per patient was 5. We found no association between pretransplantation patient characteristics and the presence of more than 5 grade ≥3 nonhematologic toxicities. Patients with elevated first-dose busulfan area under the curve values did not experience more toxicity. Paradoxically, patients treated with more than 2 regimens before undergoing ASCT had lower first-dose busulfan AUC values. With a median follow-up among survivors of 20 months, 1-year progression-free survival (PFS) and overall survival (OS) from the time of ASCT were 83% and 87%, respectively. Although this study reaffirms the favorable PFS and OS associated with TBC-conditioned ASCT for PCNSL or SCNSL, this treatment strategy carries a large toxicity burden.

Hematopoietic cell transplantation in chronic myeloid leukemia in the age of tyrosine kinase inhibitors.

The development and widespread use of tyrosine kinase inhibitors (TKIs) has relegated the use of hematopoietic cell transplant (HCT), in most countries, to chronic myeloid leukemia (CML) patients who fail or are intolerant to TKIs. Its long-term cost effectiveness compared to TKIs, however, has maintained its use as front-line treatment in some areas. Advances in HCT, including the development of intravenous busulfan and plasma assays permitting dose adjustment, have improved results of HCT in CML. Improved supportive care has lowered the incidence of non-relapse mortality and improved survival. The availability of reduced-intensity preparative regimens, molecular typing of unrelated donors, and the use of cord blood and haploidentical donors has expanded the application of HCT to nearly any patient with an appropriate indication. From 2006 to 2010, approximately one thousand HCTs were performed annually in patients with CML. Better understanding of recent advances will improve the appropriate use and results of HCT in patients with CML.

Economic and clinical aspects of intravenous versus oral busulfan in adult patients for conditioning prior to HSCT.

PURPOSE: Busulfan (BU) used as cytoreductive conditioning prior to hematopoietic stem cell transplantation (HSCT) is available as intravenous (IV) and oral (O) preparation. IV-BU has clinical advantages associated with relevant incremental costs. The aim was to determine the economic impact of IV-BU versus O-BU in adult HSCT recipients from a German health care providers' perspective. METHODS: A budget-impact model (BIM) including costs and risks for oral mucositis (OM), infection with OM, and hepatic sinusoidal obstruction syndrome (SOS) was developed. Model inputs are literature data comparing clinical effects of IV-BU versus O-BU and German cost data (conditioning therapy, treatment of OM, infections, SOS without/with multiorgan failure) from literature and tariff lists. RESULTS: Base case calculations resulted the following: total costs of adverse events were €86,434 with O-BU and €44,376 with IV-BU for ten patients each. Considering costs of adverse events and drugs, about €5840 for ten patients receiving IV-BU are saved. Sensitivity analyses were conducted in several ways. Cost savings range between €4910 and €12,640 per ten patients for all adverse events and €2070 or €1140 per ten patients considering SOS only. Drug treatment of SOS and treatment of multiorgan failure during severe SOS are major cost drivers. Worst case scenario calculations (assuming -25% risk of all adverse events for O-BU and +25% for IV-BU) yield up to €27,570 per ten patients with IV-BU. CONCLUSIONS: Considering costs of adverse events and drugs, IV-BU is the dominant alternative from a German providers' perspective. For more comprehensive economic evaluations, additional epidemiological data, evidence on clinical outcomes, patient-reported outcomes, and treatment patterns are needed.

Optimization of health-care organization and perceived improvement of patient comfort by switching from intra-venous BU four-times-daily infusions to a once-daily administration scheme in adult hematopoietic stem cell recipients.

Previous studies have shown an equivalent pharmacokinetic profile between four-times-daily (4QD) and once-daily (QD) administration of intra-venous (IV) BU, without increased toxicity. We assess the impact of a switch in IV BU from a 4QD to a QD schedule, in terms of health-care organization, staff working conditions, quality of care dispensed and perceived patient comfort. Clinicians, nurses and pharmacists from nine allogeneic transplantation units in five European countries were interviewed face to face. Overall perception of QD versus 4QD BU was very positive. Both administration schemes were evaluated to be equally efficaciousZ. QD BU was perceived to be safer and more convenient. Clinicians and nurses perceived that patient comfort was improved, due to fewer complications associated with repeated infusions, and avoiding night infusions associated with stress, anxiety and decreased quality of sleep. Switching from 4QD to QD BU had a significant impact on health-care organization, with a better integration in the overall management and usual timelines in the pharmacies and transplantation units. Time spent to prepare and administer BU was significantly reduced, leading to potential financial savings that merit further assessment and would be of particular interest in the current economic climate.

Multiple myeloma in serologic complete remission after autologous stem cell transplantation: impact of bone marrow plasma cell assessment by conventional morphology on disease progression.

The current definition of complete remission (CR) in multiple myeloma (MM) requires a negative serum and urine immunofixation (IFE) and <5% bone marrow plasma cells (BMPCs). The aim of this study was to determine the value of BMPCs count by standard microscopic evaluation in patients with MM in serologic CR after autologous stem cell transplantation (ASCT). Thirty-five patients with a median follow-up after ASCT of 7.3 years were studied. The percentage of BMPCs was an independent predictor of progression in multivariate model (hazard ratio 2.02, P = .009). Patients with >1.5% BMPCs (median: 0.8%) after ASCT had an increased risk of progression (P = .016) and a trend toward a shorter survival (P = .195). In conclusion, conventional morphology of bone marrow is a useful and rapid tool as a first step to assess the residual tumor mass in patients with MM in CR after ASCT, and it constitutes a strong predictor for disease progression.

A single apheresis procedure in the donor may be enough to complete an allograft using the "Mexican method" of non-ablative allografting.

BACKGROUND: Since 1999, in Mexico we have been using a regimen to conduct allografts that involves non-myeloablative conditioning and peripheral blood stem cells (PBSC) and have introduced some changes with the main goal of decreasing the cost of the procedure. MATERIALS AND METHODS: We analysed the salient apheresis features of a group of 175 allogeneic peripheral blood stem cell transplants conducted in two institutions in a 7-year period. The grafts were conducted using the "Mexican" non-myelo ablative conditioning regimen employing oral busulphan, i.v. cyclophosphamide and i.v. fludarabine. In all instances, the apheresis machine employed was the Baxter CS3000 Plus and donors were mobilised with filgrastim. The apheresis procedures were performed on days 0, +1 and +2, the end-point of collection being 5,000 mL of blood/m2 in each procedure. Three apheresis sessions were planned but the number was adjusted according to the cell yield. RESULTS: The final number of allografted CD34 cells ranged between 0.5 and 25.4 x 10(6)/Kg of the recipient's body weight (median, 5.2 x 10(6)/Kg). One to three apheresis procedures were needed to obtain a product containing more than 0.5 x 10(6) CD34 cells/Kg of the recipient, the median being two procedures; in 72 cases (41%) a single apheresis procedure was sufficient to obtain the target number of CD34 cells. The volumes of apheresis ranged between 50 and 600 mL (median, 400 mL). CONCLUSIONS: Since the median cost of each apheresis procedure is 900 USD, the fact that two apheresis procedures was spared in 72 cases and one apheresis was spared in another 65 cases, led to a total saving of approximately 188,100 USD. It can be concluded that, in many cases, allogeneic transplants can be completed with a single apheresis session and that there are considerable financial benefits from this practice.

Integration of modelling and simulation into the development of intravenous busulfan in paediatrics: an industrial experience.

Busulfan (Bu) is commonly used in preparative conditioning regimen prior to bone marrow transplantation in infants (< 1 year old), children and adolescents (up to 17 years old). The clinical development of an intravenous form of busulfan (Busilvex) was based on pharmacokinetic (PK) modeling and simulation techniques. A retrospective population PK analysis was initially performed from a first study in 24 pediatric patients (0.45-16.7 years old) and a log-linear relationship between body weight and Busilvex clearance was demonstrated with no age-dependency. For an optimal area under the curve (AUC) targeting, a new Bu dosing regimen [i.e. 5 dose levels (0.80 to 1.20 mg/kg) adjusted to 5 discrete weight categories] was developed and assessed through population PK-based simulations. The benefit from this new dosing strategy was validated in a second trial including 55 children (0.30-17.2 years old). This prospective trial confirmed the previous simulations: an efficient therapeutic targeting whatever the patient's age or body weight. Over 80% of the children were within the desired plasma exposure window, and the initial PK model was validated on the confirmatory dataset.

Glutathione S-transferase A1 genetic variants reduce busulfan clearance in children undergoing hematopoietic cell transplantation.

The effect of glutathione S-transferase variants on pediatric busulfan metabolism was investigated by noncompartmental and population pharmacokinetic modeling. Twenty-nine children who underwent related or unrelated bone marrow or umbilical cord blood hematopoietic cell transplant were retrospectively studied. GSTA1, GSTP1, and GSTM1 variants were explored for their effects on busulfan exposures. Noncompartmental pharmacokinetic analyses showed that carriers of GSTA1*B had a 2.6-fold higher busulfan area under the curve and concentration at steady state compared with noncarriers (P

Assessment of morphological and functional changes in the mouse testis and epididymal sperms following busulfan treatment.

BACKGROUND: Busulfan, a cytotoxic drug, which is currently used as a chemotherapeutic agent, has many side effects on different body organs. In this research, the effects of busulfan on sperm parameters and microstructure of mouse testis were investigated. METHODS: Busulfan was injected intrapretoneally at 10, 20, 30, 40 and 50 mg/kg and testes were removed after 4, 6 and 8 weeks, weighed and processed for light microscopic examination. Transverse and cross section diameters of testes, seminiferous tubules diameters, percentage of different types of tubules, epithelium thickness, spermatogenic cell numbers and capsule thickness as well as the sperm parameters in epididymis were measured. RESULTS: There was a significant decline in sperm numbers and marked changes in testes structures. Almost 8 weeks after the injection of drug, some of the changes are reversed. Accordingly, the changes in percent of normal tubules without sperm, abnormal tubules and capsule thickness were increased until 6 weeks of drug administration, the changes declined thereafter. CONCLUSION: In general, busulfan caused a decrease in all analyzed parameters (except capsule thickness, normal tubules without sperm and abnormal tubules), probably due to the arrest of spermatogenesis. Our results also revealed that some of the changes are reversible and dose dependent.

Population pharmacokinetic-based dosing of intravenous busulfan in pediatric patients.

The objective of this study was to characterize the pharmacokinetics (PK) of intravenous busulfan in pediatric patients and provide dosing recommendations. Twenty-four pediatric patients were treated with intravenous busulfan, 1.0 or 0.8 mg/kg for ages < or = 4 years or > 4 years, respectively, 4 times a day for 4 days. Dense PK sampling was performed. Body weight, age, gender, and body surface area were explored for effects on PK, and Monte Carlo simulations were performed to assess different dosing regimens. The PK of intravenous busulfan was described by a 1-compartment model with clearance of 4.04 L/h/20 kg and volume of distribution of 12.8 L/20 kg. Simulations indicated that the mg/kg and mg/m2 regimens were similar and achieved the desired target exposure in approximately 60% of patients. This model suggests that patients < or = 12 kg should be dosed at 1.1 mg/kg and those > 12 kg dosed at 0.8 mg/kg. Therapeutic drug monitoring and dose adjustment will further improve therapeutic targeting.

Clinical outcomes and direct hospital costs of reduced-intensity allogeneic transplantation in chronic myeloid leukemia.

A reduced-intensity conditioning allogeneic stem cell transplantation was given to 19 patients (aged 15-59 years) in the first chronic phase and one patient in the accelerated phase with chronic myeloid leukemia (CML) after a regimen consisting of fludarabine (Flu), busulfan (Bu) and ATG Fresenius. The median follow-up was 27 months. Until day +100, no transplant-related mortality was recorded. The incidence of acute and chronic graft-versus-host disease (GvHD) was 55 and 75%, respectively. Two patients (10%) died from GvHD. Fourteen (70%) patients achieved molecular remission. Additional post-transplant intervention (donor lymphocyte infusion, imatinib) was necessary, however, in 10 patients (50% of the patients; non-achievement of stable molecular remission or later relapses). The total direct cost of the transplantation treatment for all of the patients came to 1,572,880 euro. If the patients had been treated with imatinib and followed-up with the same time period as they were following a transplantation, the direct cost of the imatinib treatment would have been 2,005,117 euro. The transplantation treatment appears to be less expensive after approximately 2 years of follow-up. Flu+Bu+ATG is a low-toxicity regimen for patients with CML. However, a close follow-up is necessary and about 50% of the patients require further therapeutic intervention.

The modification of high-dose therapy shortens the duration of neutropaenia by delay of leucocyte nadir.

Infections during neutropaenia contribute still significantly to mortality and morbidity after high-dose therapy and autologous stem cell transplantation. Further acceleration of haemopoietic recovery seems impossible for biological reasons. Another approach to shorten neutropaenia could be to remove drugs from high-dose therapy protocols with strong contribution to immunosuppression and neutropaenia and unproven antineoplastic activity. In this retrospective matched-pair analysis, conventional busulphan/cyclophosphamide (Bu/Cy) high-dose therapy was compared to single-agent busulphan conditioning before autologous stem cell transplantation. This modification led to a significant shorter neutropaenic interval by protraction of cell decrease and to a significant mitigation of neutropaenia. After single-agent busulphan conditioning, leucocytes dropped below 1/nl at median 1.5 days later when compared to the patients from the busulphanBu/Cy control group (P=0.001). In a significant percentage of patients (n=6, 60%) leucocytes did not fall below 0.5 cells/nl at any time. In contrast, all patients from the Bu/Cy control group experienced deep neutropaenia (P=0.004). Thrombocytopaenia and requirement for transfusions of platelets or red cells were not influenced. Antineoplastic activity seemed to be preserved as determined by survival analysis. In conclusion, modification of high-dose regimen with the intention to shorten neutropaenia with preserved antitumour activity could be an approach to reduce infection-related morbidity and mortality and to consider economic necessities.

Intraindividual variability in busulfan pharmacokinetics in patients undergoing a bone marrow transplant: assessment of a test dose and first dose strategy.

Busulfan systemic exposure correlates with regimen-related toxicity, engraftment and relapse in select patients receiving high-dose oral busulfan (HD-BU) (1 mg/kg dose or 40 mg/m dose every 6 h for 16 doses) as part of a preparative regimen for bone marrow transplantation. Therapeutic drug monitoring is frequently conducted after the first HD-BU dose in order to determine necessary dose adjustments. Limitations with this method include the need for rapid determination of busulfan plasma concentration and difficulties with estimating apparent oral clearance in patients who exhibit delayed absorption of HD-BU. This pharmacokinetic study was conducted to evaluate the ability of the apparent oral clearance obtained after administering a lower (0.25 mg/kg) test dose and the traditional (1 mg/kg) first dose to predict the dose required to achieve a desired area under the concentration-time curve (AUC) at steady-state (13th dose). In addition, the pharmacokinetic parameters of test, first and 13th dose were compared to assess intrasubject variability. Twenty-nine patients received a test dose of oral busulfan (0.25 mg/kg) the day immediately prior to initiation of HD-BU. Busulfan serum concentrations were measured following the test, first and 13th doses using gas chromatography with electron capture detection. The AUC and apparent oral clearance were calculated using non-compartmental analysis. Therapeutic drug monitoring following the first dose of HD-BU was conducted for clinical purposes in six patients, and dose adjustment between the first and 13th dose occurred in only two patients. The dose-corrected test dose and first dose AUC and apparent oral clearance were not bioequivalent (two one-sided t-tests, +/-20%). The first dose and 13th dose AUC and apparent oral clearance were also not bioequivalent. Six of the 29 patients receiving HD-BU dose based on weight (1 mg/kg) would have achieved a steady-state AUC of 3600-5400 ng x h/ml, a frequently used target AUC, as compared to eight and 13 patients if their dose was based on the apparent oral clearance following the test dose and first dose HD-BU, respectively. Monitoring busulfan concentrations after a test dose or a first dose provides a better estimate of the dose needed to achieve the target steady-state AUC as compared to traditional weight-based dosing. However, significant intraindividual variability exists in the apparent oral clearance of busulfan and follow-up therapeutic drug monitoring is recommended particularly if the desired target AUC range is narrow.

Dose-reduced conditioning for allogeneic blood stem cell transplantation: durable engraftment without antithymocyte globulin.

Between February 1998 and October 1999, 24 patients with advanced leukemia, lymphoma or solid tumors received G-CSF mobilized peripheral blood stem cells (PBSC) from HLA-matched sibling donors after dose-reduced conditioning therapy. Only patients with reduced performance status or major infectious complications, not eligible for standard transplant procedures, were included. The 5-day conditioning therapy consisted of 3.3 mg/kg intravenous busulphan x 2 days and 30 mg/m2 fludarabine x 5 days. GVHD prophylaxis was performed with either CsA alone (n = 5), CsA combined with short course methotrexate (n = 5) or mycophenolate mofetil (n = 14). The day 100 survival was 95.2% for the whole group. All patients engrafted after a median of 15 days (range, 11-19) and 12.5 days (range, 10-19) for neutrophils and platelets, respectively. The median time to a neutrophil count of <0.5 x 109/l was 7 days (range, 2 to 12). Acute GVHD >I was observed in six patients, whereas eight patients have signs of chronic GVHD. The prospective 12 month overall survival with a median follow-up of 7 months is 63%. Relapse of disease and toxicity associated with chronic GVHD were the main causes of death. The treatment-related mortality was 12.5%. Dose-reduced conditioning using intravenous busulphan and fludarabine allows stable engraftment without ATG in related transplants and leads to a reduction of transplant-related mortality.

Radiotherapy followed by high dose busulfan and thiotepa: a prospective assessment of high dose chemotherapy in children with diffuse pontine gliomas.

BACKGROUND: The role of high dose chemotherapy (HDC) in patients with pediatric brain tumors currently is ill-defined. The purpose of this pilot study was to assess the feasibility and the benefit of HDC after radiotherapy in a group of children with newly diagnosed diffuse pontine gliomas. METHODS: Patients eligible for study were ages 3-18 years with diffuse intrinsic tumors arising in the pons, who were not treated previously with radiotherapy or chemotherapy. Histologic confirmation was not mandatory, provided clinical findings and magnetic resonance imaging were typical. Patients were given focal radiotherapy followed 2-3 months later by HDC. Busulfan (150 mg/m(2) on Days 8, 7, 6, and 5) and thiotepa (300 mg/m(2) on Days 4, 3, and 2) were administered prior to autologous bone marrow transplantation. Survival was the endpoint, and the statistical procedure was based on sequential subgroup analysis. RESULTS: Thirty-six patients were entered on to the study, 12 of whom underwent stereotactic biopsy or open surgery at the time of diagnosis. One patient eventually was excluded due to inappropriate eligibility criteria. All 35 eligible patients received irradiation. Early progression (9 patients) and parental refusal (2 patients) precluded the use of HDC in 11 patients. Three patients died of HDC-related complications. All 21 patients who survived HDC eventually died of disease progression. The median survival time was 10 months for the study group. The median survival time in the subgroup of patients who received HDC was 10 months (range, 3-26 months). Statistical analysis did not suggest any evidence of survival benefit. CONCLUSIONS: For patients with diffuse pontine gliomas, survival using this aggressive treatment modality does not appear to be any better than that reported for conventional radiotherapy.

Pretransplant conditioning with busulfan (Myleran) and cyclophosphamide for nonmalignant diseases. Assessment of engraftment following histocompatible allogeneic bone marrow transplantation.

Four pediatric patients with diseases potentially curable by bone marrow transplantation (BMT)--i.e., common variable immune deficiency, Wiskott-Aldrich Syndrome (WAS), mucopolysaccharidosis type VI, and mucopolysaccharidosis type I received a conditioning regimen consisting of busulfan and cyclophosphamide prior to BMT from HLA-identical, mixed leukocyte culture (MLC)-unreactive siblings. Only one of the four patients achieved full engraftment. Of the remaining three patients, one experienced failure of engraftment, and two had persistent mixed chimerism. Although no serious complications were directly related to the preparative therapy, the doses of busulfan and cyclophosphamide previously described to be adequate for conditioning children with WAS were completely effective in only one of three pediatric patients in this series. Despite a higher dose of busulfan (16 mg/kg), mixed chimerism was observed in a subsequent patient. Of 13 evaluable patients in the literature in whom busulfan and cyclophosphamide had been used as preconditioning regimens for a variety of nonmalignant conditions, eight demonstrated lack of complete and sustained engraftment. On the other hand, clinical improvement has accompanied partial engraftment in some cases. We conclude that additional immunosuppressive and/or myeloablative conditioning is necessary if complete engraftment is attempted in histocompatible allogeneic BMT for many of the nonmalignant disorders.