Busulfan disposition and hepatic veno-occlusive disease in children undergoing bone marrow transplantation

Long-term follow-up of patients with poor-risk acute leukemia treated on a phase 2 trial undergoing intensified conditioning regimen prior to allogeneic hematopoietic cell transplantation

Patients with acute leukemia who undergo allogenic hematopoietic cell transplantation with active disease have high rates of relapse and poor overall survival (OS) post-transplant compared to patients undergoing HCT in remission. Here, we report the long-term outcomes in 32 patients who received a high-intensity conditioning regimen comprising fractionated total body irradiation (FTBI; 1200 cGy) with pharmacokinetic (PK) dosing of intravenous Busulfan (IV BU) targeted to first dose area under curve (AUC) of 700-900 µM/min and etoposide (30 mg/kg) in a prospective phase 2 clinical trial. The median age of the patients at the time of HCT was 37 years (range: 18-50) presenting with high-risk (n = 6) and relapsed/refractory(r/r) acute leukemias (n = 26). All but one patient underwent HCT using peripheral blood stem cells from matched sibling donors. At a median follow-up of 17.3 years (range 14.4-19.0), 11 patients remained alive. The disease-free survival and OS at 15 years was 34% (versus 40% at 5-years post-HCT). The 15-year cumulative incidence of relapse was 26% and non-relapse mortality (NRM) was 38% (95% CI: 21-54%) and the cumulative incidence of chronic GVHD at 15 years was 33% using a prophylactic regimen of cyclosporine A and mycophenolate mofetil. The most common life-threatening late effects were secondary malignancies, metabolic, or cardiac complications with a cumulative incidence of 6.6%, 6.6%, and 13.3%, respectively. No unusual late effects or patterns of relapse were noted on longer followed on patients treated with intensified myeloablative condition regimen. Results from this study supports continued development of intensive conditioning regimens in patients with r/r acute leukemias to improve leukemia free (LFS) and OS in this high-risk population.

New dosing nomogram and population pharmacokinetic model for young and very young children receiving busulfan for hematopoietic stem cell transplantation conditioning

BACKGROUND

Busulfan (Bu) is the cornerstone of conditioning regimens prior to hematopoietic stem cell transplantation, widely used in both adults and children for the treatment of malignant and nonmalignant diseases. Despite an intravenous formulation, interindividual variability (IIV) remains high and optimal exposure difficult to achieve, especially in neonates and infants.

PROCEDURE

To ensure both efficacy and safety, we set up in 2005 an observational study designed for children not fully assessed during the drug registration procedure. From a large cohort of 540 patients, we developed a Bu population pharmacokinetic model based on body weight (BW) and maturation concepts to reduce IIV and optimize exposure. A new dosing nomogram was evaluated to better fit the population pharmacokinetic model.

RESULTS

Bu clearance IIV was significantly decreased from 61.3% (covariate-free model) to 28.6% when combining BW and maturation function. Median Bu area under the curve (AUC) was 1179 µmol/L × min compared to 1025 with the EMA dosing nomogram for children <9 kg. The target AUC was reached for each BW strata, significantly increasing the percentages of patients achieving reaching the targeted AUC as compared to FDA schedule.

CONCLUSION

This new model made it possible to propose a novel dosing nomogram that better considered children below 16 kg of BW and allowed better initial exposure as compared to existing dosing schedules. This nomogram, which would be easy to use to determine an optimal dosing schedule in daily practice, will need to be validated in clinical routine. Therapeutic drug monitoring remains strongly advisable for small children and those with specific diseases.

Targeted-dose of busulfan: Higher risk of sinusoidal obstructive syndrome observed with systemic exposure dose above 5000 µMol⸱min. A historically controlled clinical trial

Busulfan is given in the conditioning regimens preceding hematopoietic stem cell transplantation (HSCT), and plasma levels can be monitored. A targeted, individualized systemic exposure (SE) dose can be achieved by calculating the area under the plasma concentration versus time curve (AUC). The objective of this study was to determine a cutoff value for safety for the AUC for busulfan plasma levels in patients undergoing HSCT. A total of 149 consecutive HSCT patients were studied. After an oral test dose of busulfan, we set target doses of 4000, 5000, or 6000 µMol⸱min/day, and analyzed the AUC of oral or intravenous Bu. These patients were compared with 53 historical control subjects who had received myeloablative conditioning regimen without busulfan pharmacokinetic monitoring. Using a test dose and the administration route had no impact on the sinusoidal obstructive syndrome (SOS) incidence, transplant-related mortality or 1-year overall survival. However, patients receiving busulfan at doses set up at AUC > 5000 had an increased risk to develop SOS after HSCT (hazard ratio 3.39, p = 0.034, 95% CI 1.09-10.52). Adjusting the busulfan dose according to SE levels target dose during conditioning is associated with lower rates of oral severe mucositis and SOS. A cutoff of 5000 µMol⸱min is safe and does not impair survival.

Busulfan systemic exposure and its relationship with efficacy and safety in hematopoietic stem cell transplantation in children: a meta-analysis

Background

Busulfan (Bu) is a key component of several conditioning regimens used before hematopoietic stem cell transplantation (HSCT). However, the optimum systemic exposure (expressed as the area under the concentration-time curve [AUC]) of Bu for clinical outcome in children is controversial.

Methods

Research on pertinent literature was carried out at PubMed, EMBASE, Web of science, the Cochrane Library and ClinicalTrials.gov. Observational studies were included, which compared clinical outcomes above and below the area under the concentration-time curve (AUC) cut-off value, which we set as 800, 900, 1000, 1125, 1350, and 1500 μM × min. The primary efficacy outcome was notable in the rate of graft failure. In the safety outcomes, incidents of veno-occlusive disease (VOD) were recorded, as well as other adverse events.

Results

Thirteen studies involving 548 pediatric patients (aged 0.3–18 years) were included. Pooled results showed that, compared with the mean Bu AUC (i.e., the average value of AUC measured multiple times for each patient) of > 900 μM × min, the mean AUC value of < 900 μM × min significantly increased the incidence of graft failure (RR = 3.666, 95% CI: 1.419, 9.467). The incidence of VOD was significantly decreased with the mean AUC < 1350 μM × min (RR = 0.370, 95% CI: 0.205–0.666) and < 1500 μM × min (RR = 0.409, 95% CI: 0182–0.920).

Conclusions

In children, Bu mean AUC above the cut-off value of 900 μM × min (after every 6-h dosing) was associated with decreased rates of graft failure, while the cut-off value of 1350 μM × min were associated with increased risk of VOD, particularly for the patients without VOD prophylaxis therapy. Further well-designed prospective and multi centric randomized controlled trials with larger sample size are necessary before putting our result into clinical practices.

Raman spectroscopy as a potential tool for label free therapeutic drug monitoring in human serum: the case of busulfan and methotrexate

A methodology is proposed, based on Raman spectroscopy coupled with multivariate analysis, to determine the Limit of Detection (LOD) and Limit of Quantification (LOQ) for therapeutic drug monitoring in human serum, using the examples of Busulfan and Methotrexate.

Sinusoidal obstruction syndrome/veno-occlusive disease after high-dose intravenous busulfan/melphalan conditioning therapy in high-risk Ewing Sarcoma

This mono-institutional observational study was conducted to determine incidence, severity, risk factors, and outcome of sinusoidal obstruction syndrome/veno-occlusive disease (SOS/VOD) in high-risk Ewing sarcoma (ES) patients treated with intravenous busulfan and melphalan (BU-MEL) followed by autologous stem cell transplantation (ASCT). During the past 10 years, 75 consecutive ES patients resulted evaluable for the analysis. After diagnosis of SOS/VOD, defibrotide therapy was started as soon as the medication was available. The variables analyzed as potential risk factors were: gender, patient's age at diagnosis, primary tumor site, disease stage, and prior radiation therapy (RT) given, focusing on RT liver exposure. The median age at diagnosis was 18.8 years. Five patients developed moderate to severe SOS/VOD (cumulative incidence, 6.67%). None of 32 pediatric patients (≤17 years) developed SOS/VOD (p = 0.0674). In univariate analysis, prior RT liver exposure resulted statistically significant (p = 0.0496). There was one death due to severe SOS/VOD. This study reports the largest series of high-risk ES patients treated with intravenous BU-MEL before ASCT. The incidence of SOS/VOD was lower when compared with other studies that used oral busulfan. Any prior RT liver exposure should be avoided. Earlier defibrotide treatment confirms to be effective.

Computed tomography findings of hepatic veno-occlusive disease caused by Sedum aizoon with histopathological correlation

This study investigated the value of computed tomography (CT) in the diagnosis and treatment of hepatic veno-occlusive disease (HVOD) caused by Sedum aizoon (SA). The clinical manifestations, treatment results, imaging findings, and histological findings of the liver were analyzed in 39 patients with HVOD caused by SA. Hepatomegaly, liver dysfunction, abdominal effusion, and geographic density changes on liver CT scans were found in all 39 patients. The pathological findings of histological liver examination included swelling and point-like necrosis of liver cells, significant expansion and congestion of the sinuses, endothelial swelling, and wall thickening with incomplete lumen occlusion of small liver vessels. CT geographic density changes were confirmed by histological examination of the liver in 18 patients. Sixteen patients with small amounts of ascites that started within 4 weeks of treatment recovered completely or significantly improved after symptomatic and supportive treatment. However, only 43.75% of the patients with larger amounts of ascites improved following symptomatic and supportive treatment. In conclusion, liver CT examination is a valuable, safe, and noninvasive tool for the diagnosis of HVOD caused by SA. In selected cases, liver CT examination may replace liver biopsy and histological analysis.

Single Daily Busulfan Dosing for Infants with Nonmalignant Diseases Undergoing Reduced-Intensity Conditioning for Allogeneic Hematopoietic Progenitor Cell Transplantation

Busulfan (Bu) is widely used in conditioning regimens for infants undergoing allogeneic hematopoietic progenitor cell transplantation (HPCT), but the best approach to administer Bu in this population is still unknown. Here, we report a single-center experience of the use of a test dose to guide dose adjustment of intravenous (i.v.) Bu therapy in infants. Between 2004 and 2013, 33 infants younger than 1 year with nonmalignant conditions received allogeneic peripheral blood or cord blood HPCT after a reduced-intensity conditioning (RIC) regimen consisting of fludarabine, antithymocyte globulin, and 2 single daily doses of i.v. Bu. Pharmacokinetic results of a test dose of i.v. Bu (.8 mg/kg) were used to determine the dose of 2 single daily i.v. Bu regimen doses, adjusted to target an area under the curve (AUC) of 4000 μMol*minute per day in a first cohort (n = 12) and 5000 μMol*minute in a second cohort (n = 21). The mean Bu clearance in our infant patients was found to be 3.67 ± 1.03 mL/minute/kg, and the test dose clearance was highly predictive of the regimen dose clearance. The mean AUC achieved after the first single daily regimen dose was 3951 ± 1239 in the AUC 4000 cohort and 4884 ± 766 for the AUC 5000 cohort. No patient in either cohort developed hepatic sinusoidal obstructive syndrome or seizures attributable to Bu. Primary graft failure occurred in 4 patients and secondary graft failure occurred in 3, predominantly in the AUC 4000 cohort (6 of 7). Among the engrafted patients (n = 28), 16 achieved full donor chimerism and 9 patients attained stable mixed chimerism. Overall survival of patients at 6 years after transplantation was 59.5% for the AUC 4000 cohort and 85.4% for the AUC 5000 cohort, with primary graft failure in the first cohort being a major contributor to morbidity. Logistic regression analysis showed that the risk of graft failure increased significantly if cord blood hematopoietic progenitor cells were used or if total Bu exposure was below 4000 μMol*minute per day for 2 days. The difference in clinical outcomes between the 2 cohorts supports the conclusion that targeting a higher Bu AUC of 5000 μMol*minute per day for 2 days improves donor engraftment in infants with nonmalignant conditions undergoing RIC HPCT without increasing toxicity. Measuring i.v. Bu pharmokinetics using a test dose allows timely adjustment of single daily regimen doses and optimization of total Bu exposure, resulting in an effective and safe regimen for these infants.

Treosulfan-based conditioning regimen for allogeneic haematopoietic stem cell transplantation in children with sickle cell disease

Although allogeneic haematopoietic stem cell transplantation (HSCT) still represents the only consolidated possibility of cure for sickle cell disease (SCD) patients, its use has been limited by the risk of morbidity and mortality associated with conventional myeloablative therapy. The introduction of treosulfan to replace busulfan in conditioning regimens has recently been explored by virtue of its lower toxicity profile. We report our experience with a treosulfan/thiotepa/fludarabine conditioning for human leucocyte antigen (HLA)-matched sibling or unrelated donor-HSCT in 15 children with SCD, and compare patient outcomes with those of a historical cohort (15 patients) given a busulfan-based regimen. Engraftment was achieved in 28 out of 30 patients (93%), with one case of graft failure in either group. The conditioning regimen was well tolerated in both groups, with no cases of grade III-IV regimen-related toxicity. The 7-year overall survival (OS) and disease-free survival (DFS) for the whole cohort were 100% and 93%, respectively, with a 93% DFS in both busulfan and treosulfan groups. No SCD-related adverse events occurred after engraftment in patients with complete or mixed donor chimerism. This retrospective analysis suggests that a treosulfan-based conditioning regimen is able to ensure engraftment with excellent OS/DFS and low regimen-related toxicity in patients with SCD.

Association between busulfan exposure and outcome in children receiving intravenous busulfan before hematopoietic stem cell transplantation

BACKGROUND AND OBJECTIVE

Intravenous (IV) busulfan (Bu) combined with therapeutic drug monitoring-guided dosing is associated with better event-free survival (EFS), lower transplant-related mortality. But optimal target steady-state concentration (Css) of Bu in children undergoing hematopoietic stem cell transplantation (HSCT) remains unclear. This study aimed to evaluate the relation between Css of Bu and clinical outcomes in children receiving Bu before HSCT.

METHODS

This study includes 75 children receiving IV Bu in 16 doses, with first dose assigned based on age. Bu first-dose pharmacokinetic parameters were estimated from Bu plasma concentrations measured at 6 time points by high-performance liquid chromatography. Doses were adjusted at the fifth dose to a target Css of 600-900 ng/mL. Cumulative incidence of overall survival (OS), EFS, transplant-related mortality, acute graft-versus host disease (aGVHD), and other toxicities in relation to Css of Bu were analyzed using Kaplan-Meier curves in univariate and Cox's proportional hazards model in multivariate analysis.

RESULTS

After the first dose, median Css was 578 (325-1227) ng/mL. Forty-one patients had Bu IV dose increased by > 10%. Neutrophil and platelet recoveries, grade 2-4 aGVHD, and nonrelapse mortality (NRM) incidences were 90%, 91%, 12%, and 13%, respectively. Relapse incidence was 33%. Incidence of veno-occlusive disease, hemorrhagic cystitis, and lung toxicities were 13%, 24%, and 7%, respectively. OS and EFS were 70% and 58%. First-dose Bu Css >600 ng/mL was associated with a higher NRM (P < 0.001) and grade 2-4 aGVHD (P = 0.04), a lower EFS (P < 0.001), and OS (P = 0.001).

CONCLUSIONS

This study demonstrated a significant association between the first-dose pharmacokinetics of Bu and NRM, OS, and EFS. Bu therapeutic drug monitoring provides information that potentially influences outcomes of HSCT in pediatric patients.

Evaluation of effects of busulfan and DMA on SOS in pediatric stem cell recipients

BACKGROUND

Busulfan (Bu) is a DNA-alkylating agent used for myeloablative conditioning in stem cell transplantation in children and adults. While the use of intravenous rather than oral administration of Bu has reduced inter-individual variability in plasma levels, toxicity still occurs frequently after hematopoietic stem cell transplantation (HSCT). Toxicity (especially hepatotoxic effects) of intravenous (IV) Bu may be related to both Bu and/or N,N-dimethylacetamide (DMA), the solvent of Bu. In this study, we assessed the relation between the exposure of Bu and DMA with regards to the clinical outcome in children from two cohorts.

METHODS

In a two-centre study Bu and DMA AUC (area under the curve) were correlated in pediatric stem cell recipients to the risk of developing SOS and to the clinical outcome.

RESULT

In patients receiving Bu four times per day Bu levels >1,500 µmol/L minute correlate to an increased risk of developing a SOS. In the collective cohort, summarizing data of all 53 patients of this study, neither high area under the curve (AUC) of Bu nor high AUC of DMA appears to be an independent risk factor for the development of SOS in children.

CONCLUSION

In this study neither Bu nor DMA was observed as an independent risk factor for the development of SOS. To identify subgroups (e.g., infants), in which Bu or DMA might be risk factors for the induction of SOS, larger cohorts have to be evaluated.

Fludarabine and exposure-targeted busulfan compares favorably with busulfan/cyclophosphamide-based regimens in pediatric hematopoietic cell transplantation: maintaining efficacy with less toxicity

Busulfan (Bu) is used as a myeloablative agent in conditioning regimens before allogeneic hematopoietic cell transplantation (allo-HCT). In line with strategies explored in adults, patient outcomes may be optimized by replacing cyclophosphamide (Cy) with or without melphalan (Mel) with fludarabine (Flu). We compared outcomes in 2 consecutive cohorts of HCT recipients with a nonmalignant HCT indication, a myeloid malignancy, or a lymphoid malignancy with a contraindication for total body irradiation (TBI). Between 2009 and 2012, 64 children received Flu + Bu at a target dose of 80-95 mg·h/L, and between 2005 and 2008, 50 children received Bu targeted to 74-80 mg·h/L + Cy. In the latter group, Mel was added for patients with myeloid malignancy (n = 12). Possible confounding effects of calendar time were studied in 69 patients receiving a myeloablative dose of TBI between 2005 and 2012. Estimated 2-year survival and event-free survival were 82% and 78%, respectively, in the FluBu arm and 78% and 72%, respectively, in the BuCy (Mel) arm (P = not significant). Compared with the BuCy (Mel) arm, less toxicity was noted in the FluBu arm, with lower rates of acute (noninfectious) lung injury (16% versus 36%; P = .007), veno-occlusive disease (3% versus 28%; P = .003), chronic graft-versus-host disease (9% versus 26%; P = .047), adenovirus infection (3% versus 32%; P = .001), and human herpesvirus 6 infection reactivation (21% versus 44%; P = .005). Furthermore, the median duration of neutropenia was shorter in the FluBu arm (11 days versus 22 days; P < .001), and the patients in this arm required fewer transfusions. Our data indicate that Flu (160 mg/m(2)) with targeted myeloablative Bu (90 mg·h/L) is less toxic than and equally effective as BuCy (Mel) in patients with similar indications for allo-HCT.

Intravenous busulfan: a guide to its use as conditioning treatment before transplantation of haematopoietic progenitor cells

With intravenous administration of busulfan (Busilvex®), the therapeutic range of the drug is achieved in more paediatric patients than after oral busulfan administration. In clinical trials in paediatric and adult patients, intravenous busulfan-based preconditioning treatment regimen prior to haematopoietic progenitor cell transplantation (HPCT) provided high rates of engraftment, low transplant-related mortality rates and good overall survival and progression-free survival outcomes. Intravenous busulfan was considered to have an acceptable tolerability profile.

Intravenous busulfan: a guide to its use as conditioning treatment before transplantation of haematopoietic progenitor cells

With intravenous administration of busulfan (Busilvex®), the therapeutic range of the drug is achieved in more paediatric patients than after oral busulfan administration. In clinical trials in paediatric and adult patients, intravenous busulfan-based preconditioning treatment regimen prior to haematopoietic progenitor cell transplantation (HPCT) provided high rates of engraftment, low transplant-related mortality rates and good overall survival and progression-free survival outcomes. Intravenous busulfan was considered to have an acceptable tolerability profile.

Thrombosis in stem cell transplantation

Hemostatic changes and thrombotic events are frequent in patients undergoing stem cell transplantation. Arterial and venous thromboses are major causes of morbidity and mortality. Thrombotic complications can be classified into four groups including: catheter-related thrombosis, venous thromboembolic (VTE) events, sinusoidal obstructive syndrome (SOS)/veno-occlusive disease, and transplant-associated thrombotic microangiopathy (TAM). The incidence of catheter-related thrombosis is 8-20% in patients undergoing autologous hematopoietic stem cell transplantation (HSCT), and the incidence is low in syngeneic and allogeneic transplant patients. Venous duplex Doppler ultrasound, venogram, and computed tomography scan are required to visualize the venous thrombus. The treatment should be aimed at the prevention of pulmonary embolism, the avoidance of thrombus extension, and the preservation of catheter patency. Patients undergoing HSCT may have risk factors for VTE including underlying malignancy, traumatic brain injury, prolonged hospitalization, administration of conditioning regimens, and central venous catheters. Important risk factors are presence of history of VTE and graft-versus-host disease. One-year incidence of symptomatic VTE is 3.7%. SOS, also known as veno-occlusive disease, is a serious liver disease, seen in approximately 50-60% of HSCT patients. The mortality rate from the severe form of SOS is 84.3% and majority of the patients have multi-organ failure. The frequency is quite low after autologous transplantation. Risk factors for SOS include pre-existing hepatic damage, previous high-dose chemotherapy and abdominal irradiation, female gender and donor-recipient human leukocyte antigen disparity. Cyclophosphamide and busulphan are the most common agents with the highest incidence and fatal SOS. Histopathologic features of SOS include dilatation of sinusoids, necrosis of perivenular hepatocytes, and obstruction of small intrahepatic central venules by microthrombi and fibrin deposition. Signs of SOS usually occur within first 30 days after HSCT including hyperbilirubinemia, hepatomegaly, ascites, and weight gain. Symptoms of liver failure, including encephalopathy, coagulopathy, and renal failure will appear in severe form. A hepatic venous pressure gradient above 10 mmHg is highly specific for SOS. Early use of defibrotide has been shown to be effective in the treatment of high-risk SOS. TAM is a distinct, infrequent, and significant life-threatening complication of HSCT. TAM is seen in the range of 0·5-76% and was reported to be 10-25% in patients undergoing allogeneic HSCT with a mortality rate around 50%. It can also be seen after autologous HSCT and mainly affects the glomerular capillaries. There has been no standard therapy for TAM. Few case series reported good response to rituximab and high-dose corticosteroids were used with limited success. Trials with complement inhibitors such as eculizumab are currently underway.

Defibrotide for prophylaxis of hepatic veno-occlusive disease in paediatric haemopoietic stem-cell transplantation: an open-label, phase 3, randomised controlled trial

BACKGROUND

Hepatic veno-occlusive disease is a leading cause of morbidity and mortality after haemopoietic stem-cell transplantation (HSCT). We aimed to assess whether defibrotide can reduce the incidence of veno-occlusive disease in this setting.

METHODS

In our phase 3 open-label, randomised controlled trial, we enrolled patients at 28 European university hospitals or academic medical centres. Eligible patients were younger than 18 years, had undergone myeloablative conditioning before allogeneic or autologous HSCT, and had one or more risk factor for veno-occlusive disease based on modified Seattle criteria. We centrally assigned eligible participants on the basis of a computer-generated randomisation sequence (1:1), stratified by centre and presence of osteopetrosis, to receive intravenous defibrotide prophylaxis (treatment group) or not (control group). The primary endpoint was incidence of veno-occlusive disease by 30 days after HSCT, adjudicated by a masked, independent review committee, in eligible patients who consented to randomisation (intention-to-treat population), and was assessed with a competing risk approach. Patients in either group who developed veno-occlusive disease received defibrotide for treatment. We assessed adverse events to 180 days after HSCT in all patients who received allocated prophylaxis. This trial is registered with ClinicalTrials.gov, number NCT00272948.

FINDINGS

Between Jan 25, 2006, and Jan 29, 2009, we enrolled 356 eligible patients to the intention-to-treat population. 22 (12%) of 180 patients randomly allocated to the defibrotide group had veno-occlusive disease by 30 days after HSCT compared with 35 (20%) of 176 controls (risk difference -7·7%, 95% CI -15·3 to -0·1; Z test for competing risk analysis p=0·0488; log-rank test p=0·0507). 154 (87%) of 177 patients in the defibrotide group had adverse events by day 180 compared with 155 (88%) of 176 controls.

INTERPRETATION

Defibrotide prophylaxis seems to reduce incidence of veno-occlusive disease and is well tolerated. Thus, such prophylaxis could present a useful clinical option for this serious complication of HSCT.

FUNDING

Gentium SpA, European Group for Blood and Marrow Transplantation.

Weight-based strategy of dose administration in children using intravenous busulfan: clinical and pharmacokinetic results

BACKGROUND

A prospective clinical trial was performed in order to validate the pharmacokinetic (PK) and clinical benefits of a new dosing schedule of intravenous busulfan (IV Bu) in children.

PROCEDURE

IV Bu was administered as a 2-hr infusion every 6 hr for 4 days. Five dose levels were given according to body-weight strata.

RESULTS

The 67 children aged from 4 months to 17.2 years were followed up over 50 months after autologous or allogeneic stem-cell transplantation. Reduced PK variability was seen after IV Bu administration enabling efficient targeting with 78% of patients within the 900-1,500 µM · min therapeutic window and reproducible exposures across administrations. No neurological complications occurred. The low incidence of hepatic veno-occlusive disease (VOD) recorded was not correlated with high area under the curve (AUC). Only stomatitis was correlated with high AUC in the autologous group. The 4-year overall survival was 59% in the autologous group and 82% in the allogeneic group.

CONCLUSION

The new dosing schedule using IV Bu provides adequate therapeutic targeting from the first administration, with low toxicity and good disease control in high-risk children. The choice of this formulation of Bu should be considered because of its low morbidity and good outcome.

Population pharmacokinetics of busulfan in children: increased evidence for body surface area and allometric body weight dosing of busulfan in children

PURPOSE

To evaluate the best method for dosing busulfan in children, we retrospectively analyzed two different data sets from three different dosing regimens by means of population pharmacokinetics using NONMEM.

EXPERIMENTAL DESIGN

The development data set consisted of plasma samples from 94 children, in the age range of 0.4 to 18.8 years, receiving either oral or intravenous busulfan. The external model evaluation data set comprised 24 children, in the age range of 0.1 to 18.9 years, who belonged to the once-daily intravenous busulfan dosing regimen. A one-compartment model with first-order absorption using body surface area (BSA) or allometric body weight (BW) as covariate on clearance (CL) and BW as covariate on volume of distribution (V) were used to describe the results sufficiently. In addition to interindividual variability on all pharmacokinetic parameters, interoccasion variability was included for CL and V.

RESULTS

CL values in the present study did not reflect the shape of the CL versus weight curve reported in previous investigations. By external model evaluation, we were able to confirm these findings. Furthermore, bioavailability was calculated to be between 93% and 99% for the development data set. On the basis of the final models, we simulated two dosing schemes according to allometric BW and BSA showing that we estimated to include about 30% more patients into the proposed therapeutic area under the curve (AUC) range of 900 to 1,500 μM*min and could, furthermore, achieve a reduction in the AUC variability when dosed according to the labeled European Medicines Agency (EMA) dosing recommendation.

CONCLUSION

We recommend a BSA or an allometric BW dosing regimen for individualizing busulfan therapy in children to reduce variability in busulfan exposure and to improve safety and efficacy of busulfan treatment.

Therapeutic drug monitoring is essential for intravenous busulfan therapy in pediatric hematopoietic stem cell recipients

Busulfan is widely used for myeloablative conditioning in HSCT. Intravenous busulfan has been introduced to reduce interindividual variability in plasma levels especially in pediatric patients. TDM of intravenous busulfan was performed in 34 pediatric HSCT patients with malignant (n = 9) and non-malignant (n = 25) diseases (50% of patients <three yr) in a single-center analysis (2006-2009). Intravenous busulfan was administered twice daily in a four-h infusion according to recommended weight-based doses. Busulfan drug levels were measured, and pharmacokinetic analysis was performed. The targeted busulfan exposure was aimed to range between AUC of 9000-12, 000 ng/mL/h. In 23/34 patients (68%), the busulfan dose had to be adjusted at least once. In 16/23 patients (70%), the dose had to be increased in a range of 7 to 33%, while in 7/23 patients (30%), the dose had to be decreased by 7-20%. The need of dose adjustment was not related to weight, age, or underlying disease. Seven out of 34 patients (21%) <20 months experienced VOD despite that their total AUCs were within the target AUC. TDM of intravenous busulfan is essential to increase the efficacy and safety of busulfan-based conditioning protocols in pediatric HSCT recipients.

Safety, efficacy, and pharmacokinetics of intravenous busulfan in children undergoing allogeneic hematopoietic stem cell transplantation

PURPOSE

To determine the safety, efficacy, and PK profile of intravenous busulfan (Bu) in the context of a Bu and cyclophosphamide (IVBuCy) preparative regimen in children undergoing allogeneic hematopoietic stem cell transplantation (HSCT).

METHODS

Twenty-four children were enrolled in an open-label, multicenter trial of IVBuCy as the preparative regimen for HLA-matched sibling allogeneic HSCT. IVBu was administered q6 hr for 16 doses with a targeted area under the curve (AUC) of 900-1,350 microMol-min. The initial dose was 0.8 mg/kg for children >4 years of age and 1 mg/kg for those <4 years of age. PK of the first dose IVBu was determined to calculate a single dosage adjustment, and with the 9th and 13th doses to confirm steady-state PK.

RESULTS

The targeted AUC was achieved with the first dose in 17/24 (71%) of the children using the age-adjusted dosing approach. Dosing was increased in five patients, and reduced in two patients to achieve target values. After dose adjustment based on PK, 91% of the children had an AUC within the target range at steady state (AUCss). Median final dosing and clearance (CL) of IVBu were 1.1 mg/kg and 4.1 ml/min/kg in patients < or =4 years, and 0.9 mg/kg and 2.9 ml/min/kg in patients >4 years. All children were engrafted with documented donor chimerism. No late rejections or graft failures occurred. Four patients had veno-occlusive disease, three of which resolved within 2 weeks of onset. Two children died from transplant-related causes unrelated to Bu.

CONCLUSION

IVBu is a safe and effective and offers the benefit of predictable and consistent systemic exposure.

Hepatic veno-occlusive disease following stem cell transplantation: incidence, clinical course, and outcome

The occurrence of hepatic veno-occlusive disease (VOD) has been reported in up to 60% of patients following stem cell transplantation (SCT), with incidence varying widely between studies depending on the type of transplant, conditioning regimen, and criteria used to make the diagnosis. Severe VOD is characterized by high mortality and progression to multiorgan failure (MOF); however, there is no consensus on how to evaluate severity. This review and analysis of published reports attempts to clarify these issues by calculating the overall mean incidence of VOD and mortality from severe VOD, examining the effect of changes in SCT practice on the incidence of VOD over time, and discussing the methods used to evaluate severity. Across 135 studies performed between 1979 and October 2007, the overall mean incidence of VOD was 13.7% (95% confidence interval [CI]=13.3%-14.1%). The mean incidence of VOD was significantly lower between 1979-1994 than between 1994-2007 (11.5% [95% CI, 10.9%-12.1%] vs 14.6% [95% CI, 14.0%-15.2%]; P <.05). The mortality rate from severe VOD was 84.3% (95% CI, 79.6%-88.9%); most of these patients had MOF, which also was the most frequent cause of death. Thus, VOD is less common than early reports suggested, but the current incidence appears to be relatively stable despite recent advances in SCT, including the advent of reduced-intensity conditioning. The evolution of MOF in the setting of VOD after SCT can be considered a reliable indication of severity and a predictor of poor outcome.

Influence of GST gene polymorphisms on busulfan pharmacokinetics in children

Busulfan (BU) is a key compound in conditioning myeloablative regimens for children undergoing hematopoietic stem cell transplantation (HSCT). There are wide interindividual differences in BU pharmacokinetics, which increase the risk of veno-occlusive disease, graft rejection and disease relapse. As BU is mainly metabolized by glutathione S-transferase (GST), it is hypothesized that functional polymorphisms in GST genes may explain in part the variability in BU pharmacokinetics. We analyzed polymorphisms in GSTA1 (C-69T, A-513G, G-631T, C-1142G), GSTM1 (deletion) and GSTP1 (A1578G, C2293T) genes in 28 children undergoing HSCT. All patients had individualized dosing based on pharmacokinetics after the first dose of intravenous BU. GSTM1-null individuals had higher drug exposure (P(Cmax)=0.008; P(AUC)=0.003; P(Css)=0.02) and lower clearance (P(CL)=0.001). Multivariate regression models showed that, other than the drug dose and age, the GSTM1 genotype was the best predictor of first-dose pharmacokinetic variability. GSTM1-null patients also received lower cumulative BU doses (P=0.02). No association was found between BU exposure and major GSTA1 or GSTP1 gene variants. In children, GSTM1 polymorphism seems to modify BU pharmacokinetics after intravenous drug administration.

Busulfan in hematopoietic stem cell transplantation

The development of intravenous busulfan (Bu) and its incorporation in the preparative regimens for allogeneic stem cell transplantation has changed transplantation for myelogenous malignancies. Bypassing the oral route to achieve 100% bioavailability translated into improved control over drug administration, with increased safety and reliability of generating therapeutic Bu levels, maximizing antileukemic efficacy. Bu-nucleoside analog-based conditioning chemotherapy, thus far represented by fludarabine (Flu), is becoming the conditioning chemotherapy regimen of choice for patients with acute myelogenous leukemia (AML) at many transplant centers. The use of busulfan Bu-based conditioning is extending rapidly also to hematopoietic stem cell transplantation (HSCT) for lymphoid malignancies, genetic diseases, and umbilical cord blood transplantation.

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 <or= .01). Population pharmacokinetic modeling demonstrated that carriers of GSTA1*B reduced busulfan clearance by 30%. Monte Carlo simulations were then performed to assess busulfan dosing regimens based on GSTA1 genotypes. Simulations determined that dosing based on GSTA1 genotype, weight, and age resulted in fewer children exceeding the upper therapeutic limit compared with dosing using age and weight only. Larger, prospective studies are needed to confirm these findings.

Intravenous busulfan: in the conditioning treatment of pediatric patients prior to hematopoietic stem cell transplantation

An intravenous formulation of busulfan, a cytotoxic bifunctional alkylating agent, has been developed to replace oral busulfan as a conditioning treatment prior to hematopoietic stem cell transplantation (HSCT) in pediatric patients. Doses of intravenous busulfan based on actual bodyweight, but not age, reduce inter- and intraindividual variability in exposure. In a study of intravenous busulfan as a conditioning treatment prior to allogeneic or autologous HSCT, the majority of pediatric patients, who received one of five bodyweight-based doses, achieved busulfan area under the plasma concentration-time curve (AUC) values within the targeted therapeutic range. Although mean busulfan clearance values were highly variable between bodyweight strata, exposure was not affected, with no significant differences between bodyweight groups in mean AUC values. The achievement of therapeutic AUC values with intravenous busulfan resulted in a high rate of sustained engraftment, low transplant-related mortality, and promising survival outcomes post-transplant. Intravenous busulfan was considered to be well tolerated, in the particular context of HSCT, and no failure of HSCT due to organ toxicity was reported. Nonhematologic adverse events commonly associated with busulfan conditioning regimens were frequent, but generally of mild to moderate severity. The intravenous busulfan regimen was frequently associated with elevated liver enzymes, but hepatic veno-occlusive disease (HVOD) was infrequent, of mild to moderate severity, and resolved within 10 days of diagnosis. Unlike oral busulfan, intravenous busulfan does not appear to be associated with severe HVOD or death due to organ toxicity.

Hepatic veno-occlusive disease after tranexamic acid administration in patients undergoing allogeneic hematopoietic stem cell transplantation

Tranexamic acid is one of the widely used antifibrinolytic agents. In spite of its effective inhibitory activity against plasminogen, thromboembolic adverse events caused by tranexamic acid are rare. We encountered three recipients of allogeneic hematopoietic stem cell transplantation (HSCT) who developed hepatic veno-occlusive disease (VOD) shortly after the administration of tranexamic acid. Hepatic VOD was resolved completely in all patients with the discontinuation of the drug, and with supportive measures with or without intravenous tissue plasminogen activator administration. These findings suggest that administration of tranexamic acid could be one of the possible risk factors for developing hepatic VOD in HSCT recipients.

Pharmacokinetic disposition and clinical outcomes in infants and children receiving intravenous busulfan for allogeneic hematopoietic stem cell transplantation

We conducted a retrospective pharmacokinetic analysis of i.v. busulfan in children undergoing hematopoietic stem cell transplantation (HSCT) and describe its relation to transplantation outcomes. Forty-five children (median age, 3 yr) underwent HSCT at The Hospital for Sick Children from April 2003 through January 2006 and received i.v. busulfan every 6 h as part of their conditioning regimen. Initial busulfan doses were based on actual patient weight: <9 kg, 0.95 mg/kg per dose; 9-16 kg, 1.2 mg/kg per dose; 16-23 kg, 1.1 mg/kg per dose; 24-34 kg, 0.95 mg/kg per dose; >34 kg, 0.8 mg/kg per dose. Plasma busulfan concentrations were obtained after the first dose. The fourth and subsequent busulfan doses were adjusted to achieve an area under the concentration versus time curve (AUC) of 900-1500 microM.min. Development of hepatic venous occlusive disease (HVOD; modified Baltimore criteria) and engraftment (absolute neutrophil count >or=0.5 x 10(9)/L) were evaluated. Busulfan pharmacokinetic parameters were calculated using 1-compartment methods. Mean busulfan pharmacokinetic parameters were maximum concentration (C(max); 4.7 +/- 0.75 microM), volume of distribution at steady state (0.68 +/- 0.17 L/kg), elimination rate constant (0.0051 +/- 0.0010 min(-1)), total body clearance (3.5 +/- 1.23 mL/[min.kg]), and AUC (1271 +/- 280 microM.min). Mean volume of distribution at steady state was larger in children <1 yr of age (0.77 +/- 0.24 vs 0.64 +/- 0.11 L/kg; P = .040) and children <4 yr of age (0.73 +/- 0.18 vs 0.60 +/- 0.11 L/kg; P = .001) than in older children. Compared with older children, mean weight-adjusted total body clearance was higher in children <4 yr of age (3.8 +/- 1.40 versus 3.0 +/- 0.76 mL/[min.kg]). HVOD was diagnosed in 8 children (18%), including 4 children <1 yr of age. Children who developed HVOD achieved a lower C(max) than did those without HVOD (4.2 +/- 0.68 versus 4.8 +/- 0.73 microM; P = .035). Other than C(max), no association was observed between busulfan disposition and development of HVOD in children for whom i.v. busulfan doses were adjusted to achieve a target AUC. The influence of factors other than busulfan disposition on transplantation outcomes, such as genetic polymorphisms, should be evaluated.

Outcomes of hematopoietic stem cell transplantation for Hurler's syndrome in Europe: a risk factor analysis for graft failure

Hurler's syndrome (HS), the most severe form of mucopolysaccharidosis type-I, causes progressive deterioration of the central nervous system and death in childhood. Allogeneic stem cell transplantation (SCT) before the age of 2 years halts disease progression. Graft failure limits the success of SCT. We analyzed data on HS patients transplanted in Europe to identify the risk factors for graft failure. We compared outcomes in 146 HS patients transplanted with various conditioning regimens and grafts. Patients were transplanted between 1994 and 2004 and registered to the European Blood and Marrow Transplantation database. Risk factor analysis was performed using logistic regression. ‘Survival’ and ‘alive and engrafted’-rate after first SCT was 85 and 56%, respectively. In multivariable analysis, T-cell depletion (odds ratio (OR) 0.18; 95% confidence interval (CI) 0.04–0.71; P=0.02) and reduced-intensity conditioning (OR 0.08; 95% CI 0.02–0.39; P=0.002) were the risk factors for graft failure. Busulfan targeting protected against graft failure (OR 5.76; 95% CI 1.20–27.54; P=0.028). No difference was noted between cell sources used (bone marrow, peripheral blood stem cells or cord blood (CB)); however, significantly more patients who received CB transplants had full-donor chimerism (OR 9.31; 95% CI 1.06–82.03; P=0.044). These outcomes may impact the safety/efficacy of SCT for ‘inborn-errors of metabolism’ at large. CB increased the likelihood of sustained engraftment associated with normal enzyme levels and could therefore be considered as a preferential cell source in SCT for ‘inborn errors of metabolism’.

Cytotoxicity of Dimethylacetamide and Pharmacokinetics in Children Receiving Intravenous Busulfan

Purpose

To assess the cytotoxicity and the exposure of N,N-dimethylacetamide (DMA) in children during high-dose therapy with an intravenous (IV) formulation of busulfan containing the potentially hepatotoxic and neurotoxic DMA as a solvent.

Patients and Methods

Eighteen children aged 0.9 to 17.3 years (median age, 4.0 years) received IV busulfan in 15 doses of 0.7 to 1.0 mg/kg busulfan containing overall DMA amounts of between 5 mmol (437 mg) and 70.5 mmol (6,142 mg) per dose. Plasma concentrations of DMA and busulfan were quantified and analyzed using nonlinear mixed-effects modeling. Four different leukemic cell lines were incubated with DMA, and cytotoxicity was assessed in comparison with busulfan as well as in a combination reflecting the ratio in the formulation.

Results

Maximal plasma concentrations of DMA up to 3.09 mmol/L were observed. No accumulation of the solvent occurred. Instead, the trough levels decreased over the 4 treatment days. The population pharmacokinetic analysis revealed a clearance of 86.9 mL h−1kg−1± 27% that increased to 298 mL h−1kg−1on the fourth day and a volume of distribution of 469 mL kg ± 22% (population mean ± interindividual variability). DMA volume of distribution correlated with the volume of distribution of busulfan. The cytotoxicity of DMA in vitro was 3 orders of magnitude lower than that of busulfan. No synergism was observed.

Conclusion

The lack of accumulation of DMA confirms that there is no safety concern related to the DMA content in this IV busulfan formulation. The contribution of DMA to the antileukemic effect of the formulation seems to be limited.

Prospective validation of a novel IV busulfan fixed dosing for paediatric patients to improve therapeutic AUC targeting without drug monitoring

INTRODUCTION

Oral busulfan clearance is age-dependent and children experience a wide variability in plasma exposure. BSA- or age-based dosing is used with therapeutic drug monitoring (TDM) to reduce this variability.

PURPOSE

A new intravenous (IV) dosing of busulfan (Bu) based on body weight, designed to improve AUC targeting without TDM and dose-adjustment, was prospectively evaluated.

METHOD

Bu was administered as a 2 h IV infusion every 6 h over 4 days (16 administrations). Five dose levels were defined on body weight as follows: 1.0 mg/kg for <9 kg; 1.2 mg/kg for 9 to <16 kg; 1.1 mg/kg for 16-23 kg; 0.95 mg/kg for >23-34 kg; 0.80 mg/kg for >34 kg. Bu treatment was followed by Cyclophosphamide or Melphalan prior to allogeneic or autologous transplantation in 55 children aged 0.3-17.2 years (median 5.6 years).

RESULTS

No difference in AUC values was observed between weight strata (mean +/- SD 1248 +/- 205 micromol.min), whereas a significant difference in Bu clearance was demonstrated. This new dosing enabled to achieve a mean exposure comparable to that in adults. At dose 1, 91% of patients achieved the targeted AUC range (900-1500 micromol.min) while no patients were underexposed. At doses 9 and 13, over 75% of patients remained within that target whilst most of the others were slightly above. Successful engraftment was achieved in all patients. In conclusion, from infants to adults this new dosing enabled, without TDM and dose adjustment, to successfully target a therapeutic AUC window.

Elevated plasma ferritin and busulfan pharmacodynamics during high-dose chemotherapy regimens in children with malignant solid tumors

Hepatic veno-occlusive disease (HVOD) is a frequent complication during hematopoietic stem-cell transplantation (HSCT). A strong relationship has been demonstrated between busulfan exposure and HVOD for busulfan-cyclophosphamide and allogeneic HSCT in adults. Busulfan disposition after the first intake was studied in 77 children treated for solid malignancies with high-dose busulfan-containing regimens and autologous HSCT. Busulfan was combined with cyclophosphamide and melphalan (n=30), melphalan (n=27), and thiotepa (n=20). No relationship was observed between busulfan exposure and HVOD. In contrast, plasma ferritin at baseline was higher in patients with HVOD (750 ng/ml (20-3,110)) compared with those without HVOD (189 ng/ml (8-3,967), P=0.012). Multivariate analysis showed that a ferritin level exceeding 300 ng/ml was the only risk factor for HVOD with an odds ratio of 4.0 (confidence interval 95% (1.5-11.2), P=0.0071). A high ferritin level at baseline was explained by the diagnosis of neuroblastoma, related treatments and transfusions.

Pharmacokinetics of a Test Dose of Intravenous Busulfan Guide Dose Modifications to Achieve an Optimal Area Under the Curve of a Single Daily Dose of Intravenous Busulfan in Children Undergoing a Reduced-Intensity Conditioning Regimen with Hematopoietic Stem Cell Transplantation

We studied 30 pediatric patients with malignant (n = 16) or nonmalignant (n = 14) conditions. The preparative regimen consisted of fludarabine, intravenous (IV) busulfan (Bu) for 2 daily doses, and antithymocyte globulin before stem cell transplantation. A test dose of IV Bu (0.8 mg/kg), anticipated to target an area under the concentration-time curve (AUC) of 800 to 1200 micromol.min, was followed later by 2 daily doses adjusted according to the pharmacokinetics (PK) to target an AUC of 3200 to 4800 micromol.min. The median test dose AUC was 953 micromol.min (range, 439-1315 micromol.min). The median AUC of single daily doses was 3798 micromol.min (range, 1511-7254 micromol.min). PK-based dose modification was required in 20 patients: 12 were adjusted to a higher dose, and in 8 the dose was decreased. Nausea and vomiting were noted in 15 patients. No patient developed hepatic veno-occlusive disease or seizures. Full donor chimerism was attained in 20 patients (mean of 24.5 days), 3 achieved partial chimerism, 5 did not engraft, and in 2 it is too early to assess chimerism. Acute graft-versus-host disease developed in 11 patients, grades I to II developed in 10 patients, and grade III developed in 1. Four patients died of infection and 5 of progressive disease. Thus, PK of a test dose of IV Bu provided information to adjust subsequent daily doses of IV Bu: this resulted in a regimen that was feasible, safe, and convenient for administration to children.

Quantification of Busulfan in Saliva and Plasma in Haematopoietic Stem Cell Transplantation in Children

BACKGROUND AND OBJECTIVE

Busulfan pharmacokinetic studies suggest that an individual dosing strategy may be necessary to optimise systemic exposure in order to decrease toxicity and improve outcome in haematopoietic stem cell transplantation. Therapeutic and toxic effects of the busulfan/cyclophosphamide regimen have been related to the area under the busulfan plasma concentration-time curve. Because of practical limitations in obtaining blood from children, saliva was evaluated as an alternative matrix for therapeutic drug monitoring, offering the advantages of a non-invasive, rapid and easy sampling procedure. Another objective was to evaluate an easy and robust liquid chromatography- tandem mass spectrometry method for plasma and saliva busulfan determination.

METHODS

An online extraction cartridge with column-switching technique, analytical liquid chromatography over a Chromolith RP 18 e column, and tandem mass spectrometry were used to quantify busulfan concentrations in matched plasma and saliva samples. The study population consisted of ten patients, aged 1.3-19 years (median age 11.8 years, seven females, three males), undergoing haematopoietic stem cell transplantation. All patients received busulfan 0.8-1.3 mg/kg orally every 6 hours for a total of 16 doses, followed by two doses of cyclophosphamide (60 mg/kg/day).

RESULTS

The lowest limit of detection was 2 microg/L and the lower limit of quantification was 10 microg/L. Only 100 microL of plasma/saliva was needed. The mean recoveries (SD) of busulfan were 97.2% (2.7) in plasma and 100.4% (1.3) in saliva. Intra- and inter-assay imprecision was 2-3% and 2-4% for plasma, and 1-2% and 2-4% for saliva (concentration range 30-1,500 microg/L). The bias was <4% for both plasma and saliva. The correlation between the busulfan concentration in plasma and saliva was highly significant (r=0.958; p<0.0001; saliva/plasma ratio=1.09+/-0.04; n=69 sample pairs). The apparent plasma clearance was slightly higher than the apparent saliva clearance (202+/-31 mL/h/kg vs 189+/-28 mL/h/kg; p=0.001). The mean elimination half-life was found to be 2.31+/-0.46 hours for plasma and 2.30+/-0.36 hours for saliva; these were not significantly different (p=0.83).

CONCLUSION

The present study demonstrated that busulfan analysis in saliva could be a valuable and reliable alternative to plasma analysis.

Myeloablative and immunosuppressive properties of treosulfan in mice

OBJECTIVE

Treosulfan is a prodrug with a specific clinical activity in ovarian carcinoma and other solid tumors. Due to its myeloablative and immunosuppressive effects, its use in conditioning regimens prior to allogeneic stem cell treatment (SCT) has been proposed. In the present preclinical study, myeloablative as well as immunosuppressive properties of treosulfan were compared with those of busulfan and cyclophosphamide.

METHODS

Three groups of BALB/c mice were treated with treosulfan, cyclophosphamide, or busulfan at sublethal doses that maintained survival without bone marrow support. The control group was left untreated. At different intervals, colony-forming unit granulocyte macrophage assay was performed on marrow cells. Additionally, immunological analyses were performed using spleen cells.

RESULTS

We found that treosulfan and busulfan induced a high and persisting degree of myeloablation, as compared with cyclophosphamide. Moreover, treosulfan was more effective in depletion of splenic B and T cells in comparison with busulfan and cyclophosphamide. Furthermore, T cells isolated from the spleens of treosulfan- or busulfan-treated mice were not responsive to allogeneic cells compared with that observed in controls and cyclophosphamide-treated mice. Treatment with treosulfan induced only interleukin-2 production in spleen cells for a short time and had no significant effect on synthesis of tumor necrosis factor-alpha and/or interferon-gamma as compared with that observed in splenic T cells isolated from mice treated with either busulfan or cyclophosphamide.

CONCLUSION

Our findings suggest that treosulfan possesses both myeloablative and immunosuppressive properties and may be used as a single agent for conditioning prior to bone marrow transplantation.

Platelet transfusion containing ABO-incompatible plasma and hepatic veno-occlusive disease after hematopoietic transplantation in young children

BACKGROUND

Hepatic veno-occlusive disease is a major limiting factor of high-dose chemotherapy in children. The cells lining the hepatic vascular endothelium express blood group A and/or B antigens according to the patient's blood group. We designed a study evaluating the impact of platelet concentrates containing ABO-incompatible plasma transfused to young children with a high risk of hepatic veno-occlusive disease.

METHODS

In all, 186 consecutive children (median age: 4 years, range: 0.75-17 years), treated with high-dose chemotherapy containing busulfan followed by hematopoietic stem cell transplantation for neuroblastoma (n=112) or brain tumor (n=74) between 1988 and 1998, were investigated. The main endpoint was the occurrence of hepatic veno-occlusive disease. Multivariate analysis was performed using a Cox's regression model with transfusion of platelet concentrates containing ABO-incompatible plasma as a time-dependent covariate.

RESULTS

We found that 73 out of 186 (39%) children developed hepatic veno-occlusive disease after transplantation. Multivariate analysis demonstrated that two factors significantly increased the risk of hepatic veno-occlusive disease occurrence: transfusion of platelet concentrates containing ABO-incompatible plasma (P=0.003) and use of melphalan in the conditioning regimen (P=0.006). Conversely, the number of platelet concentrates transfusions per week, child's age, weight, sex, and use of cyclophosphamide in the conditioning regimen had no effect.

CONCLUSIONS

Transfusion of platelet concentrates containing ABO-incompatible plasma increases the risk of hepatic veno-occlusive disease in young children treated with a busulfan-containing regimen. Binding of A and/or B antigens expressed on the surface of hepatic endothelial cells may promote this complication. Transfusion of platelet concentrates containing ABO-incompatible plasma should be avoided in these children.

Portal vein thrombosis during antineoplastic chemotherapy in children: Report of five cases and review of the literature

We report five paediatric cases of portal vein thrombosis (PVT) occurring during chemotherapy, observed in two institutions over an 8-year time period. These children aged 2.5-15 years were treated for Burkitt's lymphoma, Ewing's tumour, small cell bone tumour or medulloblastoma. PVT was diagnosed on colour Doppler ultrasonography (US). In four patients, thrombosis occurred 2-45 days after severe hepatic veno-occlusive disease (HVOD) secondary to intensive chemotherapy containing busulfan. In one case, PVT occurred in the absence of HVOD in a patient with pre-existing periportal lymphomatous infiltration. Four patients experienced persistent portal hypertension, which resulted in death in one. PVT during chemotherapy in children is a rare event and appears to be closely related to intensive chemotherapy containing busulfan and to be associated with HVOD.