Maximally tolerated busulfan systemic exposure in combination with fludarabine as conditioning before allogeneic hematopoietic cell transplantation.
ABSTRACT Systemic exposure to high-dose busulfan has been correlated with efficacy and toxicity after hematopoietic cell transplantation for malignancy. We used the area under the concentration-time curve (AUC) to prospectively determine the maximally tolerated systemic exposure to i.v. busulfan when given once daily after fludarabine administered at 40 mg/m(2) for 4 days. Three target AUC levels were planned: 6,000, 7,500, and 9,000 μM-min. Included were patients 16 to 65 years old, with a hematologic malignancy, an HLA A, B, or C, DRB1 8/8 or 7/8 matched donor, Karnofsky performance status ≥70%, and adequate organ function. For level 1 patients, i.v. busulfan doses 1 and 2 were 170 mg/m(2)/day, then doses 3 and 4 were adjusted based on first-dose pharmacokinetic modeling to achieve an average daily AUC of 6,000 μM-min. Doses 1 and 2 for the subsequent cohorts were based on the level 1 data: 180 mg/m(2)/day for AUC 7,500 μM-min (level 2) and 220 mg/m(2)/day for AUC 9,000 μM-min (level 3), with pharmacokinetic targeting for doses 3 and 4. Pharmacokinetic analysis after the last dose showed that 88% of the patients had been exposed to a mean AUC within 10% of the target. Forty patients were treated at level 1, 29 patients at level 2, and three patients at level 3. DLT was veno-occlusive disease of the liver, which occurred in none of 40 patients (0%) at level 1, two of 29 patients (7%) at level 2, and three of three patients (100%) at level 3. Dermatitis (P < .01) and pulmonary toxicity (P = .01) were also increased at higher AUC levels. Level 2 (7,500 μM-min × 4 days) was the maximally tolerated AUC. Within the confines of the trial's small sample size, there was no suggestion that escalating busulfan AUC from 6,000 to 7,500 μM-min × 4 days increased nonrelapse mortality. Assessment of the higher busulfan AUC on relapse prevention requires trials in patients with a homogeneous risk of relapse.
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ABSTRACT: Targeted busulfan/cyclophosphamide ((T)BU/CY) for allogeneic hematopoietic cell transplantation (HCT) carries a high risk of sinusoidal obstruction syndrome (SOS) in patients transplanted for myelofibrosis. We tested the hypothesis that reversing the sequence of administration (from (T)BU/CY to CY/(T)BU) will reduce SOS and day +100 non-relapse mortality (NRM). We enrolled 51 patients with myelofibrosis (n=20), acute myeloid leukemia (AML, n=20), or myelodysplastic syndrome (MDS, n=11) in a prospective trial of CY/(T)BU conditioning for HCT. Cyclophosphamide 60 mg/kg/day IV for two days was followed by daily IV BU for four days, targeted to a concentration at steady state (Css) of 800-900 ng/mL. CY/(T)BU-conditioned patients had higher exposure to CY (p<0.0001) and lower exposure to 4-hydroxyCY (p<0.0001) compared to (T)BU/CY-conditioned patients. Clinical outcomes were compared with controls (n=271) conditioned with (T)BU/CY for the same indications. In patients with myelofibrosis, CY/(T)BU conditioning was associated with a significantly reduced incidence of SOS (0% vs. 30% after (T)BU/CY, p=0.006), while SOS incidence was low in both cohorts with AML/MDS. Day +100 mortality was significantly lower in the CY/(T)BU cohort (2% vs. 13%, p=0.01). CY/(T)BU conditioning markedly impacted CY pharmacokinetics and was associated with significantly lower incidences of SOS and day +100 mortality, suggesting that CY/(T)BU is superior to (T)BU/CY as conditioning for patients with myelofibrosis.Biology of blood and marrow transplantation: journal of the American Society for Blood and Marrow Transplantation 04/2013; · 3.15 Impact Factor
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ABSTRACT: I.v. BU plus fludarabine is an effective conditioning regimen for myeloid neoplasias with low treatment-related mortality. At standard doses, cutaneous toxicity has been reported in <5% of cases. As we observed a much higher incidence of cutaneous toxicity in patients who received predominantly pharmacokinetically based doses of BU, we performed a retrospective analysis of 61 patients who received i.v. BU plus fludarabine (+/- antithymocyte globulin; ATG) as a conditioning regimen before allogeneic PBSC transplant. Of the 58 evaluable patients, 33 (57%) developed cutaneous toxicity that fell within the spectrum of toxic erythema of chemotherapy (TEC). The median onset of TEC was 22 days and most patients had multiple sites of involvement, with the groin, axillae and palms/soles being the favored sites. In men, scrotal involvement, sometimes severe, was also commonly observed. Initially, allergic reactions to antibiotics, fungal infections and GVHD were also considered until the clinical presentation of TEC became well recognized. In all patients, the skin healed without specific therapy but resolution often required several weeks. This series suggests that TEC is common after BU/fludarabine+/- ATG and it is important for transplant physicians to recognize, particularly as misdiagnosis could lead to inappropriate treatment.Bone Marrow Transplantation advance online publication, 19 November 2012; doi:10.1038/bmt.2012.218.Bone marrow transplantation 11/2012; · 3.00 Impact Factor
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ABSTRACT: This study evaluated the influence of fludarabine on the pharmacokinetics of busulfan administered orally to patients receiving a conditioning regimen for hematopoietic allogeneic stem cell transplantation (HSCT). Twenty-six patients treated with oral busulfan (1 mg/kg/6 h for 4 days) were divided into two groups according to the concomitant administration of fludarabine (n = 11; 30 mg/m(2) for 5 days) or subsequent administration of cyclophosphamide (n = 15; 60 mg/kg for 2 days). Serial blood samples were collected on Day 4 of busulfan administration. Plasma busulfan concentrations were determined by HPLC-UV and the pharmacokinetic parameters were calculated using the WinNonlin program. Patients concomitantly treated with fludarabine showed reduced apparent clearance of busulfan (110.5 mL/h/kg vs. 157.4 mL/h/kg) and higher AUC0-6 (area under the plasma concentrations vs. time curve) than patients subsequently treated with cyclophosphamide (7.9 µg h/mL vs. 5.7 µg h/mL). No association was observed between busulfan AUC0-6 and clinical evolution of the patients. Although plasma busulfan concentrations were higher in patients receiving concomitant fludarabine, myelosuppression-related toxicity was less frequent than in patients treated with busulfan and cyclophosphamide. The results suggest that patients treated with fludarabine should receive 30% lower busulfan doses during conditioning protocols for HSCT.The Journal of Clinical Pharmacology 08/2013; · 2.84 Impact Factor