An Evaluation of Engraftment, Toxicity and Busulfan Concentration in Children Receiving Bone Marrow Transplantation for Leukemia Or Genetic Disease
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Bone Marrow Transplantation (2000) 25, 925–930 2000 Macmillan Publishers Ltd All rights reserved 0268–3369/00 $15.00 www.nature.com/bmt An evaluation of engraftment, toxicity and busulfan concentration in children receiving bone marrow transplantation for leukemia or genetic disease AM Bolinger1, AB Zangwill1, JT Slattery2,3, D Glidden4, K DeSantes5, L Heyn6, LJ Risler3, B Bostrom7 and MJ Cowan8 1University of California at San Francisco, Department of Clinical Pharmacy; 2Department of Pharmaceutics, University of Washington; 3Fred Hutchinson Cancer Research Center; 4University of California at San Francisco, Department of Epidemiology and Biostatistics; 5University of Wisconsin, Department of Pediatrics; 6University of California at San Francisco, Department of Nursing; 7University of Minnesota, Department of Pediatrics; and 8University of California at San Francisco, Department of Pediatrics, San Francisco, CA, USA Summary: children exhibit average busulfan steady-state concen- trations (Css) or an area under the curve (AUC) substan- Autologous recovery is a major problem with busulfan tially less than do older children or adults.7–9 The Css corre- as a marrow ablative agent in conditioning children for sponds to the AUC over a dosing interval divided by the allogeneic BMT. Data suggest the average concentration 6 h between doses. The AUC over a dosing interval is equal of busulfan at steady state (Bu Css) is critical for suc- to the AUC from the time the first dose is ingested to infin- cessful engraftment. We prospectively evaluated busul- ity if no subsequent doses are taken. A Css of 900 ng/ml fan pharmacokinetics in 31 children (age 0.6–18 years) is equal to an AUC of 1350 m × min. with AML (n = 9), and non-malignant diseases (n = 22) Few studies of the relationship between busulfan receiving HLA-closely matched (sibling, parent, Css (Bu Css) or AUC and outcome of the busulfan/ unrelated) donor grafts. Blood samples were obtained cyclophosphamide preparative regimen have focused on following dose 1 and 13 of a standard 16 dose, 4-day children. Adults with CML have been shown to be at regimen. The busulfan dose varied from 14 to 20 mg/kg. increased risk of relapse if Bu Css is low and exhibit less Patients received cyclophosphamide 200–240 mg/kg; busulfan-related toxicity compared to patients with other 22/31 received 80–90 mg/kg of ATG. Eight patients diseases receiving similar treatment.10,11 Excessively low failed to engraft (26%). ATG did not appear to influ- = Ͻ levels of busulfan have been related to graft rejection, while ence engraftment (P 0.38). Bu Css levels 600 ng/ml high levels have been related to severe toxicities.12,13 Of correlated with autologous recovery/mixed chimerism particular interest in children is the issue of graft rejection. (P = 0.018). There were no graft failures in patients with Since cyclophosphamide is directly toxic to mature lym- a Bu Css Ͼ600 ng/ml. A correlation between Bu Css phocytes and busulfan is not, graft rejection has been levels and regimen-related toxicity (RRT) was not ident- thought to be due to inadequate dosing of cyclophospham- ified for grade 2 or higher toxicities, only 1/31 had a Bu 1,14 Css Ͼ900 ng/ml. Our data support the use of pharmaco- ide. Thus, the relatively high incidence of graft rejection kinetic monitoring of busulfan. Bone Marrow Transplan- in children receiving a busulfan/cyclophosphamide prepara- tation (2000) 25, 925–930. tive regimen has resulted in the use of higher doses of Keywords: busulfan; children; bone marrow transplan- cyclophosphamide than are used in adults. ATG also has tation; cyclophosphamide; toxicity been added to the regimen in an attempt to gain additional immune suppression. However, graft rejection is still rela- tively frequent, even with total doses of cyclophosphamide as high as 200–240 mg/kg and ATG. We therefore sought Busulfan is a potent myelotoxin that complements the lym- to determine whether graft rejection was associated with phocyte toxicity of cyclophosphamide in preparative regi- low Bu Css in children receiving 14–20 mg/kg busulfan mens for hematopoietic stem cell transplantation.1–3 The and 200–240 mg/kg cyclophosphamide, whether toxicities standard dose is 1 mg/kg administered orally every 6 h over (primarily to the gastrointestinal (GI) mucosa, liver and 4 days. However, this regimen results in highly variable lung) were associated with high busulfan levels and concentrations in plasma, particularly when young children whether ATG facilitated engraftment in our patients who are compared to older children or adults.4–7 At a given dose, were conditioned with busulfan and cyclophosphamide. normalized to either body weight or surface area, young Correspondence: Dr AM Bolinger, University of California, San Franci- sco, School of Pharmacy, 521 Parnassus, Room C-152 Box 0622, San Francisco, CA 94143-0622, USA Received 18 October 1999; accepted 19 January 2000 Busulfan concentration and BMT outcome in children AM Bolinger et al 926 Methods ning at 9 a.m. on the first day of conditioning. In the 31 patients evaluated, the total oral busulfan dose varied from Patients and treatments 14 to 20 mg/kg. Busulfan was followed by cyclophospham- ide administered i.v. at 50 to 60 mg/kg on 4 consecutive We prospectively evaluated busulfan pharmacokinetics in days (only one patient received a total dose of 240 mg/kg); n = 38 pediatric patients (age 0.6 to 18 years) with AML ( 22/31 patients (71%) received a total dose of 80 to 90 14) and non-malignant diseases (n = 24) who were receiv- mg/kg ATG (Table 1). A compounded suspension of oral ing HLA-matched or closely matched sibling (n = 28), par- busulfan was administered through a nasogastric tube in n = n = ent ( 3), or unrelated ( 4) donor marrow grafts. Donor children unable to reliably swallow tablets. All other cell dose was approximately 5 × 108 per kilogram for all patients received doses as commercially available 2 mg tab- patients. Patient demographics are described in Table 1. All lets. Patients were NPO for at least 1 h before and 1 h after patients enrolled in BMT protocols from May 1991 to April busulfan administration. Graft-versus-host disease (GVHD) 1996 that included busulfan as a conditioning agent were prophylaxis was methotrexate (MTX) (n = 1); cyclosporine eligible. Seven patients were excluded: two received auto- (CsA) (n = 3); or a combination of CsA/MTX (n = 25), logous transplants, one received a syngeneic transplant, two CsA/MTX/methylprednisolone (n = 3) or CsA/prednisone received a T cell-depleted transplant, one received mel- (n = 1). Phenytoin (PHT), dose adjusted to maintain thera- phalan and one was excluded due to problems in obtaining peutic levels, was administered to nine patients (29%) as samples. Parents of all patients provided informed consent prophylaxis against busulfan-related seizures. for participation in this study which was approved by the Committee on Human Research at the University of Cali- fornia, San Francisco. Patients over 12 years of age also Samples and pharmacokinetic analysis provided assent to participate. Busulfan was administered as part of the BMT prepara- Blood samples were collected for analysis in heparinized tive regimen as the standard 16 dose, 4 day regimen begin- tubes at times 0, 30, 60, 120, 180, 240, 300 and 360 min Table 1 Patient demographics UPN Age (years) Diagnosis Donora Weight (kg) Bu/Cy dose ATG (mg/kg) GVHD Other (mg/kg) prophylaxis 123 0.9 AML 1 8.7 16/200 0 MTX 124 1.9 Hurlers 2 13.2 16/200 80 MTX/CsA 126 0.8 SCID 1 8 16/200 80 MTX/CsA 131 2 AML 1 10.9 16/200 0 CsA 143 8.2 ALD 1 22.7 18/240 80 MTX/CsA 146 6.8 B-Thalassemia 1 19.5 16/200 80 MTX/CsA 152 1.3 AML 1 12.9 16/200 0 CsA 153 0.8 B-Thalassemia 1 9.6 16/200 80 MTX/CsA 155 2.9 B-Thalassemia 1 14.6 16/200 80 MTX/CsA 156 12 B-Thalassemia 1 24 16/200 80 MTX/CsA 165 12.5 EPHL 1 45.7 16/200 0 MTX/CsA VP-16/PHT 170 12 BFD 1 32 16/200 80 MTX/CsA PHT 175 17 AML 1 82.7 16/200 0 MTX/CsA 181 2.7 B-Thalassemia 1 16 16/200 80 MTX/CsA 188 10 B-Thalassemia 1.4 30.3 16/200 80 MTX/CsA 191 2.2 WAS 1.3 12.9 16/200 80 MTX/CsA 195 12.3 Sickle cell anemia 1 54b 14/200 90 MTX/CsA PHT 198 17.9 AML 1 42.6 16/200 0 MTX/CsA PHT 199 0.7 WAS 2 7.6 20/200 80 MTX/CsA/MP PHT 205 5.9 BFD 1 15 16/200 80 MTX/CsA 208 5.3 B-Thalassemia 1 17 16/200 80 MTX/CsA 209 7.8 B-Thalassemia 1 20 16/200 80 MTX/CsA 214 11.7 AML 1 42 16/200 0 MTX/CsA 215 3.5 B-Thalassemia 1 17.6 16/200 80 MTX/CsA 218 1.6 Hurlers 2 12.1 20/200 80 MTX/CsA/MP PHT 223 2.9 AML 2 14 16/200 80 MTX/CsA/MP 229 1.1 B-Thalassemia 1 11.2 16/200 80 MTX/CsA PHT 232 0.7 CID 1 8 16/200 80 MTX/CsA 239 4.9 AML 1 17.9 16/200 0 MTX/CsA 241 16.3 AML 1 62 16/200 0 CsA/PDN PHT 252 6.2 Sickle cell anemia 1 18.6 16/200 90 MTX/CsA PHT UPN = unique patient number; Bu = busulfan; CY = cyclophosphamide; ATG = anti-thymocyte globulin; GVHD = graft-versus-host disease; AML = acute myelogenous leukemia; SCID = severe combined immunodeficiency syndrome; ALD = adrenoleukodystrophy; EPLH = erythrophagocytic lymphohi- stiocytosis; BFD = Blackfan–Diamond syndrome; WAS = Wiskott–Aldrich syndrome; CID = combined immunodeficiency disease; MTX = methotrexate; CsA = cyclosporine; MP = methylprednisolone; PDN = prednisone; PHT = phenytoin.