The pharmacokinetics and pharmacodynamics of busulfan when combined with melphalan as conditioning in adult autologous stem cell transplant recipients.

Busulfan (Bu) is an alkylating agent widely used in conditioning regimes prior to stem cell transplantation (SCT), most commonly in combination with cyclophosphamide (Bu-cy) or fludarabine (Bu-flu) as myeloablative conditioning prior to allograft or with high-dose melphalan (Bu-mel) prior to autologous SCT. Despite many decades of Bu use, initially orally but now intravenously (IV), a paucity of pharmacokinetic (PK) and pharmacodynamic (PD) data exists to inform evidence-based guidelines as how best to balance the efficacy and toxicity of this agent. This is a non-randomized retrospective real-world study at three hospitals investigating the role of PK guidance in dosing Bu in the setting of IV Bu-mel autologous SCT. The primary intent was to examine how effectively PK assessment could be used to achieve a desirable drug exposure and to evaluate factors, particularly, age, sex, actual weight, body mass index (BMI), body surface area (BSA), disease, number of prior treatments, renal function, and the use of concomitant medications that may influence Bu exposure. All patients underwent PK analysis on a test dose of Bu (1.6 mg/kg, i.e., 50% of the first dose) on D-7 and subsequently received a second 1.6 mg/kg dose on D-6. Bu dose was calculated using actual body weight (ABW) if patients were less than ideal body weight (IBW), or adjusted ideal body weight (AIBW) if ABW was greater than IBW. Thereafter, at the discretion of the investigator, the group was divided into two; a weight-based cohort at two hospitals and a PK-guided cohort at the third hospital. Thirty-seven patients received PK-adjusted dosing guided by the results of the initial PK results, targeting a specific Bu exposure expressed as the area-under-the-concentration-versus-time curve (AUC) of between 4000 and 5000 µmol min/day (median 4800). The remaining 27 patients received unadjusted weight-based doses with a further three doses of 3.2 mg/kg of Bu infused over 180 min (D-5 to - 3) irrespective of their initial PK results. For the purposes of the analysis, we selected a target AUC of 4800 µmol min/day in this group, equivalent to the median targeted AUC in the PK-adjusted group. All patients subsequently had repeated PK analysis on D-5 after receiving their "therapeutic" Bu dose. Mel (140 mg/m2 or 100 mg/m2) IV was given on D-2. Sixty-four adult patients were enrolled. Patients who received PK-guided Bu dosing received a higher median Bu dose than the unadjusted weight-based cohort (3.5 mg/kg vs 3.2 mg/kg respectively, p = 0.007). Eighty-one percent (30/37) of patients in the PK-guided group achieved their target AUC (± 15%) compared with 56% (15/27) in the weight-based cohort (p = 0.027). The respective median AUCs of 5064 µmol min/day (range 3639-6157 µmol min/day) and 4854 µmol min/day (range 3251-6305 µmol min/day) were not significantly different (p = 0.16). Multivariate analysis identified ABW as the only independent variable that affected the relationship between Bu dosing and exposure (p = 0.02) with heavier patients achieving lower than anticipated AUCs for the dose they received. On D-5, within the weight-based cohort, the mean AUCs were 12% higher than anticipated based on initial D-7 PK. No correlation between AUC and grade 3-4 transplant-related toxicities were observed, although only three patients had AUCs > 6000 µmol min/day. These results suggest that PK-directed Bu dosing may be of benefit in achieving a target level of drug exposure, with larger studies needed to determine the clinical significance of this strategy.

The effect of folinic acid on methylenetetrahydrofolate reductase polymorphisms in methotrexate-treated allogeneic hematopoietic stem cell transplants.

This study examined the contribution single nucleotide polymorphisms (SNPs) of the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene have on clinical outcomes in hematopoietic stem cell transplant patients treated with the antiproliferative drug methotrexate. Two common SNPs, 677C>T and 1298A>C, were genotyped by polymerase chain reaction-restriction fragment-length polymorphism (PCR-RFLP) from samples obtained from patient DNA samples. Eleven clinical outcomes including survival and graft-versus-host disease (GVHD) were assessed against donor and recipient MTHFR genotypes against pretransplantation variables. Folinic acid (FA) as treatment for oral mucositis toxicity was used at investigator discretion in 72 of 140. Donor MTHFR 1298AA genotype was associated with decreased 5-year survival (P = .03) and event-free survival (EFS) (P = .02) in patients withheld FA. Donor MTHFR 677CC genotype was associated with earlier GVHD (P = .003), and more severe acute GVHD (P = 0.02). FA was significantly associated with decreased survival (P = 0.02) in patients given a donor MTHFR 677CT transplant. FA was significantly associated with decreased survival (P = .04), EFS (P = .009) in patients given a donor MTHFR 1298AC transplant MTHFR gene polymorphisms indicate a potentially useful gene for donor selection where more than one donor is available. Use of FA following transplantation should be reconsidered in the context of patient and donor MTHFR genotypes.

Improved survival for relapsed diffuse large B cell lymphoma is predicted by a negative pre-transplant FDG-PET scan following salvage chemotherapy.

The utility of ([18F])fluoro-2-deoxy- d-glucose positron-emission tomography (FDG-PET) for predicting outcome after autologous stem cell transplantation (ASCT) for diffuse large B cell lymphoma (DLBCL) is uncertain - existing studies include a range of histological subtypes or have a limited duration of follow-up. Thirty-nine patients with primary-refractory or relapsed DLBCL with pre-ASCT PET scans were analysed. The median follow-up was 3 years. The 3-year progression-free survival (PFS) for patients with positive PET scans pre-ASCT was 35% vs. 81% for those who had negative PET scans (P = 0.003). The overall survival (OS) in these groups was 39% and 81% (P = 0.01), respectively. In a multivariate analysis, PET result, number of salvage cycles and the presence of relapsed or refractory disease were shown to predict a longer PFS; PET negativity (P = 0.04) was predictive of a longer OS. PET is useful for defining those with an excellent prognosis post-ASCT. Although those with positive scans can still be salvaged with current treatments, PET may useful for selecting patients eligible for novel consolidation strategies after salvage therapies.

Genetic heterogeneity of granulocytes for the JAK2 V617F mutation in essential thrombocythaemia: implications for mutation detection in peripheral blood.

AIMS: The molecular pathogenesis of essential thrombocythaemia (ET) is heterogeneous. We aimed to determine the relative sensitivity of four separate molecular assays used to detect the presence of the JAK2 V617F mutation in peripheral blood from patients with essential thrombocythaemia and related myeloproliferative disorders. METHODS: Purified granulocytes from 60 patients were analysed for the presence of the JAK2 V617F mutation by direct sequencing, denaturing high-performance liquid chromatography (DHPLC), allele-specific polymerase chain reaction (PCR) and allele-specific enrichment. Clinical data were collected for all patients and correlated with assay results. RESULTS: Direct sequencing and DHPLC were relatively insensitive assays for mutation detection, together identifying only 53% of the JAK2 V617F positive cases of ET. Allele-specific PCR and allele-specific enrichment were significantly more sensitive assays and were able to identify additional ET patients that were positive for the JAK2 V617F mutation in only a minority of circulating granulocytes. Enrichment for the mutation was demonstrated in blood platelets from two of these patients. CONCLUSIONS: The observed biological difference in circulating granulocyte involvement by the JAK2 V617F clone necessitates a sensitive molecular assay for the diagnostic investigation of thrombocytosis.