Mini Review Myeloablative conditioning regimens for AML allografts: 30 years later

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1 (2003) 32, & 2003 Nature Publishing Group All rights reserved /03 $ Mini Review Myeloablative conditioning s for AML allografts: 30 years later V Gupta 1, HM Lazarus 2 and A Keating 1 1 Department of Medical Oncology and Hematology, Princess Margaret Hospital/Ontario Cancer Institute, Toronto, Ontario, Canada; and 2 Case Western Reserve University, Cleveland, OH, USA Summary: During the last three decades, several myeloablative conditioning s have been used for AML allografts. In this review, we systematically examine the data from studies reporting on myeloablative conditioning s for AML allografts. High-dose busulfan combined with cyclophosphamide (BuCy) and cyclophosphamide in combination with total body irradiation (CyTBI) are the two most commonly used conditioning s for AML allografts. From the available data, there are no significant differences in survival with these two s. A small benefit of decreased relapse rate with CyTBIis counterbalanced by a nonsignificant increase in treatmentrelated mortality. The incidence of veno-occlusive disease is significantly higher in patients treated with BuCy. Therapeutic monitoring of busulfan was not reported in any of the studies comparing the s. Either of the s can be used for AML allografts, and the choice may ultimately depend on local availability and expertise. Further improvements may be possible from modifications of the standard s. Data from these latter studies seem to be encouraging, but are not based on comparative randomized trials. (2003) 32, doi: /sj.bmt Keywords: AML; conditioning ; busulfan; cyclophosphamide; total body irradiation a conditioning can influence the incidence and severity of GVHD. 6 The morbidity and mortality associated with allobmt therefore, depends a great deal on the choice of conditioning. 7,8 Despite the long-standing use of allobmt in AML, the optimal myeloablative conditioning remains unknown.few data from comparative or randomized studies are available to address this issue. The outcome of transplantation in AML is dependent upon a complex interaction of many disease-, patient- and treatment-related factors. 9 Over the past decade, pretreatment cytogenetics has emerged as one of the most robust prognostic determinants of outcome for AML Cytogenetics data, however, were either not reported or unavailable in a large proportion of patients in studies comparing the conditioning s in AML.Also, several studies used different definitions of good-risk and high-risk AML.Owing to the multiple factors affecting outcome of allobmt for AML (Table 1), interpretation of these data can be difficult in the absence of well-designed randomized studies.studies addressing this question in other diseases such as CML 13,14 may not be applicable to AML because of differences in the biology of the disease and the intensity of pre-transplant treatment. The objective of this review is to examine the studies reporting on myeloablative conditioning s for AML allografts and to determine whether one particular is superior. Allogeneic bone marrow transplantation (allobmt) is the most intensive postremission therapy used for AML for more than 30 years. 1,2 The relapse-risk with this treatment is considerably lower than with autologous bone marrow transplant (ABMT) or chemotherapy alone, although high treatment-related mortality (TRM) continues to be a major limitation. 3 5 TRM is related to the direct toxicities of the conditioning s and includes interstitial pneumonitis, veno-occlusive disease (VOD) and graftversus-host disease (GVHD).Furthermore, the toxicity of Correspondence: Dr V Gupta, Department of Medical Oncology and Hematology, Rm.5-224, 610-University Avenue, Toronto, Ontario, Canada M5G 2M9; vikas.gupta@uhn.on.ca Search strategy and selection criteria Studies for this review were identified by searches of PubMed/Medline, EMBASE databases and appropriate references from the relevant articles.only papers in English were reviewed and only studies reporting on the allograft conditioning s in AML with at least 20 patients in a disease specific setting (eg CR1 or advanced disease) were included. Evolution of myeloablative conditioning s in acute leukemia Cyclophosphamide and total body irradiation (CyTBI) has long been used as a myeloablative conditioning or

2 970 Table 1 preparatory after the initial reports of encouraging results of allobmt in acute leukemia. 1,2,15 Based on studies in rats and initial allotransplant trials in patients with relapsed acute leukemia, 19,20 a myeloablative dose of busulfan (16 mg/kg p.o. over 4 days) was established. The total daily dose of busulfan is usually given in four divided doses, mainly for ease of administration of the large total dose.the busulfan/cyclophosphamide (BuCy) was considered an effective alternative to radiation-based s for AML. 21 While initial studies with BuCy used Cy at a dose of 200 mg/kg (50 mg/kg daily 4 days, also known as BuCy 4), 21,22 further attempts were made to refine this by decreasing the dose of Cy to 120 mg/ kg (60 mg/kg daily 2 days, also known as BuCy 2), which appeared to be equally effective and less toxic It is noteworthy that there has been no randomized comparison of BuCy 4 with BuCy 2.The CyTBI and BuCy s have become the two most commonly used standard myeloablative s in AML (IBMTR database, personal communication, Horowitz, MM). Comparison of BuCy vs CyTBIin AML The s will be compared for survival outcomes, treatment-related complications and relapse rate, according to the remission status, a powerful factor affecting treatment outcome. 21,26 AML CR1 Factors affecting outcome of allobmt in AML Clinicobiological features Cytogenetics at diagnosis de novo AML vs secondary AML Remission status at transplant Host Age Performance status Graft Source of stem cells PB or BM Dose of stem cells Type of donor related or unrelated Graft manipulation such as T-cell depletion Supportive care GVHD prophylaxis These two conditioning s in AML in CR1 were compared in two randomized 27,28 and two registry-based studies 29,30 in adults and one registry-based study 31 in children.the main limitation of the randomized studies from the French 27 and Nordic group 28 and the registrybased pediatric study is the small number of subjects.in contrast, the observational database studies from the EBMT 29 and IBMTR 30 groups have large numbers of patients but selection bias remains an issue despite careful matching for patient and disease characteristics. The biases relate to unknown factors that influence the choice of one particular over the other by the treating physician or center and are not possible to exclude from these studies.other center-specific effects that may affect outcome 32 are also difficult to eliminate from these studies.problems in the interpretation of data from the literature on conditioning s in AML are highlighted in Table 2.Results from the five studies comparing BuCy with CyTBI are summarized in Table 3. Survival outcomes.the multicenter randomized French study is the only study in adults that showed the superiority of CyTBI (n ¼ 50) over BuCy (n ¼ 51) in disease-free survival (DFS) (72 vs 47%, Po0.01) and overall survival (OS) (75 vs 51%, Po0.02). The superior survival was attributed to a lower relapse rate (14 vs 34%, Po0.04) and low TRM (8 vs 27%, Po0.06) in favor of the CyTBI arm. 27 In contrast, the randomized study on a cohort of patients with AML and other leukemias (AML CR1 patients, BuCy (n ¼ 25), CyTBI (n ¼ 26)) from the Nordic group did not show a significant difference in the outcome of patients with early-disease treated with these two s. 28 The results for AML in CR1 are difficult to interpret in this study because several parameters were reported on a mixed cohort of patients with AML, CML and ALL with different remission status.subsequent comparative studies from the EBMT 29 and IBMTR 30 groups did not show any significant difference in survival with these two treatment s. Treatment-related complications.no difference in the incidence of GVHD, either acute or chronic, was observed with these two s in the registry database studies. 29,30 The randomized comparative studies showed more deaths from GVHD in the BuCy Group 27 and a higher number of cases with grades III V agvhd or cgvhd. 28 It is also noteworthy that the diagnosis of GVHD was mainly clinical in these studies.in the absence of a pathologic diagnosis, it may be difficult to differentiate between VOD (consistently higher in the BuCy group) and GVHD. Moreover, how VOD modifies the course and severity of GVHD is not known. Table 2 Limitations of studies on conditioning s in AML 1.Small number of study patients in randomized studies 2.Mixed cohorts of patients with different remission status 3.Different definitions of end points 4.Center-specific effects in retrospective comparisons a.bias of selection of one over other Availability Personal preference b.different perceptions of role of BMT in various risk-groups c.practice of TBI Lung shielding Source of TBI Different doses and fractionation schedules of TBI d.monitoring of busulfan blood concentration e.supportive care differences Antimicrobial prophylaxis Growth factor use f.t-cell depletion g.gvhd prophylaxis

3 Table 3 Comparison of BuCy and CyTBI in AML CR1 971 Study (study population) Design (outcome at n years) Conditioning n TRM (%) RR (%) DFS or EFS (%) OS (%) Comments Blaise et al 27 Ringden et al 28 Ringden et al 29 Litzow et al 30 Michel et al 31 (children) Randomized (outcome at 2 years) Randomized (outcome at 3 years) Comparative (outcome at 2 years) Comparative (outcome at 5 years) Comparative (outcome at 5 years) BuCy CyTBI superior for survival, relapse rate and TRM CyTBI BuCy2 25 NR* NR* 83 NR* Busulfan equally effective alternative to TBI in early disease, that is, CR1 (results reported for mixed cohort of patients) CyTBI 26 NR* NR* 58 NR* BuCy NR No difference in TRM, DFS or relapse rate. BuCy NR CyTBI NR BuCy CyTBI superior for lower relapse, no difference in survival CyTBI BuCy NR BuCy2 associated with significantly higher-risk of relapse, no difference between BuCy4 and TBI containing BuCy NR TBI** NR TRM, treatment-related mortality; RR, relapse rate; DFS, disease-free survival; EFS, event-free survival; OS, overall survival; NR, not reported; NR*, results reported for mixed cohort of patients but not separately for AML CR1 patients; TBI**, with TBI 24 patients received Cy, four Cy and additional drug and four melphalan; BuCy2, cyclophosphamide 120 mg/kg with busulfan; BuCy4, cyclophosphamide 200 mg/kg with busulfan. It is noteworthy that TRM in the CyTBI arm (8%) was significantly lower in the French study, but this has not been matched in other studies (Table 3).The cause of this discrepancy is not clear.the fractionation of TBI and lung shielding reduce the incidence of interstitial pneumonitis in TBI-based s. 33,34 Lung shielding was used in all cases in the TBI group in the French study 27 compared with 60% of evaluable cases in the IBMTR registry study. 30 The lungs receive 10 20% higher dose of radiation than the prescribed dose, because they are air-containing organs.the practice of lung shielding to eliminate this overdose effect is not universal and varies at different centers.it seems unlikely that this factor alone led to lower TRM in the TBI group in the French study and may be a chance association due to the small number of patients studied.while the EBMT study described a significantly higher proportion of cases of interstitial pneumonitis in the CyTBI arm, 29 this was not observed in the IBMTR study. 30 Other complications appear to be more frequent in patients receiving BuCy.A consistent finding in all these studies was the significantly higher incidence of VOD of the liver with BuCy compared to CyTBI Also, a significantly higher incidence of hemorrhagic cystitis was observed with the BuCy. 28,29 In addition, seizures occur in a significantly higher proportion of patients receiving busulfan. 28 Engraftment.There were no differences in the engraftment rate between the two groups in the EBMT study, 29 although the IBMTR study showed a significant difference in earlier neutrophil recovery in the BuCy cohort. 30 Relapse rate.the French randomized trial and the IBMTR registry study, but not the EBMT registry study showed significantly lower relapse rates in the CyTBI arm. A different pattern of relapse, especially increased relapses at extramedullary (EM) sites, particularly the central nervous system (CNS), was observed in patients receiving BuCy compared to CyTBI. 30 A high incidence of EM relapses was also observed in patients with AML treated with BuCy conditioning at a single center. 35 These observations suggest that TBI-based s are more effective in treating occult CNS disease. It is noteworthy that in the French study, the dose of Cy was 120 mg/kg (BuCy2).It is unlikely however, that this led to the increased relapses in the BuCy arm as previous studies suggested that the efficacy of BuCy2 may be similar to BuCy Furthermore, both registry studies found no difference in the outcome of patients treated with the lower dose of Cy. 29,30 Nevertheless, the pediatric registry study, based on a small number of patients, demonstrated the superiority of BuCy4 to BuCy2 in a comparison of BuCy2, BuCy4 and TBI-based conditioning s for patients with AML in CR1. 31 This study showed a significantly higher risk of relapse with BuCy2, but no difference between BuCy4 and CyTBI.Plasma busulfan levels, however, were not monitored in any of these studies.inter- and intrapatient variability in the kinetics of busulfan may explain the different results among the various studies.

4 972 Long-term complications.concerns have been raised at the increased risk of secondary malignancies in patients treated with TBI-based s. 36,37 There are few data on the comparative risk of secondary malignancies with these two s.long-term follow-up of patients treated with these two s in the French study did not show significant difference in the number of cases of second malignancy. 38 In the absence of clear evidence that one causes more cases of cancer, it is important to keep patients treated with either under long-term surveillance for secondary malignancies. While long-term follow-up in the Nordic study found significantly more cases of obstructive bronchiolitis in the BuCy group and cataracts in TBI cohort, 39 no such long-term differences were observed in AML patients treated with these two conditioning s in the French study. 38 Quality of life and costs.the quality of life (QOL) and health care utilization costs have not been studied prospectively in any of these studies.in a combined longterm analysis of the French and Nordic studies, equal proportions of AML patients treated with CyTBI or BuCy returned to work/school (85 vs 88%). 40 Beyond CR1 Very scanty data are available to determine whether patients with advanced AML (second or later remissions, early relapse) benefit preferentially from TBI- or chemotherapy-based s.in the EBMT comparative study, no difference in TRM, relapse or LFS was observed in patients receiving CyTBI (n ¼ 46) compared with BuCy (n ¼ 46). 29 In the Nordic study, the TBI-based was superior for patients with advanced disease in a mixed cohort (beyond CR1 or CML patients beyond first chronic phase), however, the number of AML patients with advanced disease in this study was too small to reach any meaningful conclusions (BuCy, n ¼ 12; CyTBI, n ¼ 6). 28 Other comparative studies of myeloablative conditioning s in AML AML CR1 The question of the optimum dose and schedule of TBI was addressed by two randomized studies from the Seattle group.in the first randomized study, AML patients in CR1 were randomized between cyclophosphamide and single exposure 10 Gy TBI (n ¼ 27) vs 12 Gy TBI in six fractions in combination with cyclophosphamide (n ¼ 26). 41 This study showed a significant survival advantage for patients treated with the fractionated TBI. In an effort to increase the antileukemic efficacy of TBI, AML patients in CR1 were randomized to receive 12 Gy TBI in six fractions (n ¼ 34) vs Gy TBI in seven fractions (n ¼ 37). 8 Indeed, the relapses in the cohort receiving higher dose of TBI was significantly lower, however, this did not translate into a survival benefit because nonrelapse mortality from agvhd was higher.updated results of this study reported the same trend. 42 In another prospective study, the CyTBI (n ¼ 36) was compared with melphalan and TBI (n ¼ 27) in AML CR1. 43 Neither the actuarial probability of remaining in remission (66 vs 94%, P40.1), nor the OS was significantly different between the two groups (53 vs 55%). Beyond CR1 A randomized study from the Southwest Oncology Group (SWOG) of 114 leukemia patients (including AML, ALL and CML) not in first remission, compared ftbi (1320 cgy of TBI in 11 fractions) and VP-16 (60 mg/kg) for one dose vs BuCy2. 44 The investigators stratified the patients to good-risk (CR2 or accelerated phase) and poor-risk (CR3, induction failure, in relapse, blast phase) categories and showed equivalent survival outcomes with the ftbi and BuCy s (55 vs 34%, P ¼ 0.30). There were a total of 40 AML patients (good-risk (n ¼ 11), poor-risk (n ¼ 29)) in this trial.owing to the limited number of patients, the results were not analyzed according to the type of leukemia. Modifications of standard myeloablative s in AML In an effort to improve the efficacy of the s, several investigators have modified standard protocols by 1.Replacing cyclophosphamide with agents such as VP Intensifying the s with (a) Additional chemotherapy. (b) Radioimmunotherapy. 3.Using newer strategies with busulfan. 4.T-cell depletion. Replacing cyclophosphamide with VP-16 The ftbi/vp-16 was studied in 99 patients with acute leukemia in CR1 (AML, n ¼ 61). 45 The was well tolerated and for AML patients, cumulative probabilities for DFS and relapse rates at 3 years were 61 and 12% (Table 4).This has not been tested in AML CR1 patients in comparative studies.another pilot study reported encouraging results (3 years DFS 56% and relapse rate 25%) by using VP-16 with busulfan for AML autografts. 46 However, this has not been tested for AML allografts. Intensification of standard myeloablative s with (a) Additional chemotherapy.attempts were subsequently made to improve the efficacy of standard s by the addition of other agents such as VP16 (etoposide), Thiotepa, 51 and cytarabine. 52 These s were well tolerated and results from these studies are summarized in Tables 4 and 5, according to remission status.the German group have reported impressive results using a combination of VP-16 with BuCy2 in AML CR1 in a mixed group of patients (adults and children). 48,49 Of particular note, none

5 Table 4 Studies using chemotherapy modifications of standard myeloablative s in AML CR1 973 Study (study population) Design (outcome at n years or months) Conditioning n TRM (%) RR (%) DFS or EFS (%) OS (%) Comments Snyder et al 45 (adults and children) Zander et al 48 (adults and children) Kroger et al 49 (adults and children) Single arm (outcome at 3 years) Single arm (outcome at 30.5 months) Comparison of two doses of VP16 added to BuCy2 (outcome at 3 years) FTBI+VP (i) Mixed population of adults and children, median age 26.3 years ( ) (ii) Age a significant prognostic variable (iii) Not tested with a standard myeloablative BuCy2+VP16 (VP mg/kg) BuCy2+VP mg/kg vs BuCy+VP mg/kg (i) Well-tolerated, (ii) Adult and pediatric patients combined, median age 30 years (4 51) (iii) Not compared with a standard myeloablative NR (i) Highly efficacious, no relapses NR (ii) Lower dose of etoposide (30 mg/kg) better tolerated (iii) Adult and pediatric patients combined (iv) Not compared with a standard myeloablative TRM, treatment-related mortality; RR, relapse rate; DFS, disease-free survival; EFS, event-free survival; OS, overall survival; NR, not reported. of the patients relapsed in these two studies.the data suggest that VP mg/kg for one dose with BuCy2 is well tolerated.another study reported severe pulmonary toxicity of this in patients with a prior history of chest irradiation undergoing ABMT and allobmt. 53 The dose of VP-16 in this study was 40 mg/kg for one dose along with BuCy2. (b) Radioimmunotherapy.Targeted radioimmunotherapy, either in combination with radiation-based or chemotherapy-based s is another means of increasing the radiation dose without increasing toxicity. 54 Clinical trials using 131 I-labeled anti-cd33 antibody M195, I-labeled anti-cd45 antibody 56,57 and 188 Rhenium-labeled anti- CD66 antibody 58 in combination with the CyTBI and BuCy s demonstrate the feasibility of this approach.these approaches mainly use b-emitting isotopes conjugated to monoclonal antibodies.more recently, an a- particle emitter, 213 Bi in conjugation with Hum195, was shown to be active in a phase I study in advanced myeloid leukemias. 59 Unlike b-particle emitting isotopes, a emitters can selectively kill individual cancer cells.the use of a- particle-based targeted radiation with conditioning s has not yet been studied.these strategies appear promising and may further improve the efficacy of the conditioning s, but are restricted to larger centers because of the requirement for special facilities. Newer strategies with busulfan A major limitation of p.o. busulfan is wide interpatient variability of pharmacokinetics due to unpredictable intestinal absorption, dosing uncertainties due to emesis, erratic bioavailability and a narrow therapeutic window.a suboptimal dose of busulfan expressed as a low area under the curve (AUC) resulted in a higher frequency of graft rejection and relapses 60 and a higher AUC correlated with increased toxicity, mainly VOD and seizures The pharmacokinetics of busulfan are also age-dependent and children tend to clear busulfan faster. 61 Some of these issues may be addressed by monitoring blood busulfan levels using limited sampling models followed by dose adjustment to achieve a targeted steady-state concentration. 64,65 Cyclophosphamide levels however, are not routinely monitored after conditioning therapy.it was recently shown in patients treated with CyTBI protocols that increased exposure to toxic metabolites of cyclophosphamide resulted in increased liver toxicity and nonrelapse mortality. 66 Whether a targeting strategy with cyclophosphamide similar to the approach used with busulfan will result in better survival is currently not known. More recently, intravenous (i.v.) preparations of busulfan have become available.four different formulations of busulfan have been tested in phase I/II studies The safety profile of i.v. preparations of busulfan is favorable with fewer acute side effects and better engraftment. A comparative retrospective analysis of i.v. busulfan vs p.o. busulfan in the BuCy2 showed a significantly lower VOD (8 vs 33%, P=0.002) and significantly superior 100-day survival in favor of i.v. preparation. 71 It is important to note that busulfan levels were not reported in this study. The superiority of i.v. busulfan over p.o. busulfan with targeted levels is not known at present

6 974 Table 5 Studies using chemotherapy modifications of standard myeloablative s in AML beyond CR1 Study (study population) Design (outcome at n years or months) Conditioning N TRM (%) RR (%) DFS or EFS (%) OS (%) Comments Brown et al 50 Bibawi et al 51 Single arm (outcome at 44 months) Etoposide+ CyTBI NR Patients in untreated first relapse Single arm (outcome at 3 years) Thiotepa+ BuCy a 43 a NR 26 a (i) Active in advanced AML (ii) Comparable TRM to standard myeloablative s (iii) Dose of busulfan reduced to 12 mg/kg (iv) Results reported for combined AML and advanced MDS patients TRM, treatment-related mortality; RR, relapse rate; DFS, disease-free survival; EFS, event-free survival; OS, overall survival; NR, not reported. a Results reported for mixture of patients with AML and advanced MDS. and this remains a key study question for future clinical trials in this area. Initial studies with i.v. busulfan used the four times daily dosing schedule as with p.o. busulfan. A recent study reported once daily i.v. busulfan (3.2 mg/kg i.v. 4 days) with fludarabine as a myeloablative conditioning for hematologic malignancies. 72 Pharmacokinetic studies on a subset of patients showed linear kinetics with this approach with cumulative AUC comparable to that established for p.o. busulfan. The once daily may help to further simplify the treatment. T-cell depletion As GVHD is one of the main factors that influences TRM, approaches to decrease the incidence and severity of GVHD by decreasing the number of T cells in the donor marrow have caught investigative attention.several methods of T-cell depletion such as negative selection by physical separation or antibody-based purging have been tried. 73 The results of clinical trials using this approach in AML patients in CR1 are summarized in Table No additional GVHD prophylaxis to CR1 patients was given in these trials.the main problem with this approach remains the higher risk of relapse, graft failure and immune reconstitution. 77 Graft rejection with T-cell depletion allografts may be overcome by increasing pretransplant immunosuppression and myeloablation with ATG and thiotepa. 76,78 All AML patients in these two studies achieved primary and sustained engraftment with full donor chimerism.moreover, GVHD was either significantly reduced (grade I agvhd o5%, no cases of grades II IV agvhd, cgvhd 3%) 76 or not seen at all. 78 Despite the increased scientific knowledge gained over the last two decades in this area, the exact role of T-cell depletion in allotransplants for AML remains unclear. Novel strategies for conditioning s More recently, several groups have focused on nonmyeloablative or reduced intensity conditioning s.the main aim is to exploit the beneficial graft-versus-leukemia (GVL) effect and reduce -related complications such as GVHD.These approaches offer patients who are not candidates for myeloablative transplants due to age or concomitant medical problems, the opportunity to benefit from a GVL effect. 79,80 Experience with AML however is limited A high relapse rate continues to be a major issue with nonmyeloablative protocols. 84,85 Although the comparison of nonmyeloablative and myeloablative protocols for the incidence of GVHD is difficult because of different patient eligibility criteria, a recent study showed that the cumulative incidence of grades II IV agvhd was significantly in favor of nonmyeloablative transplants (64 vs 85%, P ¼ 0.001). 86 Nonetheless, there was no difference in cgvhd requiring treatment (73 vs 71%).More disease-specific and long-term data are needed to fully evaluate the efficacy of these approaches. At present, myeloablative conditioning s, clinically tested for over 30 years, remain the gold standard of treatment and allotransplants with novel strategies for patients at high risk of TRM should only be offered as a part of a clinical trial. Conclusion Based on an assessment of the literature, survival with the two most commonly used myeloablative conditioning s, BuCy and CyTBI, are similar.local availability and expertise may determine the preference of one over the other.neither is suitable for all the situations and a particular should be avoided in selected clinical situations; for example, BuCy should be avoided in a patient with abnormal liver function and CyTBI, in patients with a prior history of radiation to the lung. Modification of these s by intensification with additional chemotherapy or radioimmunotherapy, newer preparations of busulfan and T-cell depletion may enhance efficacy and tolerability.whether these modifications will result in better survival in AML patients remain to be established in randomized studies.

7 Table 6 Studies evaluating myeloablative conditioning s with T-cell depletion in AML CR1 975 Study (study population) Design (outcome at n years or months) Conditioning n TRM (%) RR (%) DFS or EFS (%) OS (%) Comments Young et al 74 Soiffer et al 75 Papadopoulos et al 76 Single arm (outcome at 3 years T-cell depletion of BM grafts (physical method) Single arm (outcome at 4 years CD6 depleted donor grafts by T12 monoclonal antibody) Single arm (outcome at 4 years T-cell depletion of BM grafts) (physical method) CyTBI 31 a (i) 12 patients died of treatment related causes (ii) Graft rejection major cause of treatment failure CyTBI mainly BuCy 1 patient ATG & Thiotepa+ CyTBI b Several results reported for combined AML and ALL patients NR (i) Low relapse rate (ii) agvhd grade I o5%, no cases of II IV agvhd (iii) cgvhd 3% TRM, treatment-related mortality; RR, relapse rate; DFS, disease-free survival; EFS, event-free survival; OS, overall survival; agvhd, acute GVHD; cgvhd, chronic GVHD. a 12/31 patients died of causes related to transplant and one indeterminate cause. b Reported for mixture of AML and ALL patients. Acknowledgements We thank Dr JM Rowe for a careful review of the manuscript and helpful comments.ak holds the Gloria and Seymour Epstein Chair in Cell Therapy and Transplantation at University Health Network and University of Toronto. References 1 Thomas ED, Buckner CD, Banaji M et al. One hundred patients with acute leukemia treated by chemotherapy, total body irradiation, and allogeneic marrow transplantation. Blood 1977; 49: Thomas ED, Buckner CD, Clift RA et al. Marrow transplantation for acute nonlymphoblastic leukemia in first remission. N Engl J Med 1979; 301: Zittoun RA, Mandelli F, Willemze R et al. Autologous or allogeneic bone marrow transplantation compared with intensive chemotherapy in acute myelogenous leukemia. European Organization for Research and Treatment of Cancer (EORTC) and the Gruppo Italiano Malattie Ematologiche Maligne dell Adulto (GIMEMA) Leukemia Cooperative Groups. N Engl J Med 1995; 332: Cassileth PA, Harrington DP, Appelbaum FR et al. Chemotherapy compared with autologous or allogeneic bone marrow transplantation in the management of acute myeloid leukemia in first remission. N Engl J Med 1998; 339: Burnett AK, Wheatley K, Goldstone AH et al. The value of allogeneic bone marrow transplant in patients with acute myeloid leukaemia at differing risk of relapse: results of the UK MRC AML 10 trial. Br J Haematol 2002; 118: Ferrera J, Antin J. Pathophysiology of Graft-vs-Host Disease. Hematopoietic Stem Cell Transplantation.Blackwell Scientific Publications: Boston, MA, 1999, pp Gluckman E.Influence of conditioning on the outcome of allogeneic bone marrow transplantation. Int J Radiat Oncol Biol Phys 1990; 19: Clift RA, Buckner CD, Appelbaum FR et al. Allogeneic marrow transplantation in patients with acute myeloid leukemia in first remission: a randomized trial of two irradiation s. Blood 1990; 76: Appelbaum FR.Is there a best transplant conditioning for acute myeloid leukemia? Leukemia 2000; 14: Grimwade D, Walker H, Oliver F et al. The importance of diagnostic cytogenetics on outcome in AML: analysis of 1,612 patients entered into the MRC AML 10 trial.the Medical Research Council Adult and Children s Leukaemia Working Parties. Blood 1998; 92: Slovak ML, Kopecky KJ, Cassileth PA et al. Karyotypic analysis predicts outcome of preremission and postremission therapy in adult acute myeloid leukemia: a Southwest Oncology Group/Eastern Cooperative Oncology Group Study. Blood 2000; 96: Byrd JC, Mrozek K, Dodge RK et al. Pretreatment cytogenetic abnormalities are predictive of induction success, cumulative incidence of relapse, and overall survival in adult patients with de novo acute myeloid leukemia: results from Cancer and Leukemia Group B (CALGB 8461). Blood 2002; 100: Clift RA, Buckner CD, Thomas ED et al. Marrow transplantation for chronic myeloid leukemia: a randomized study comparing cyclophosphamide and total body irradiation with busulfan and cyclophosphamide. Blood 1994; 84: Devergie A, Blaise D, Attal M et al. Allogeneic bone marrow transplantation for chronic myeloid leukemia in first chronic phase: a randomized trial of busulfan-cytoxan vs cytoxan-total body irradiation as preparative : a report from the French Society of Bone Marrow Graft (SFGM). Blood 1995; 85: Beutler E, Blume KG, Bross KJ et al. Bone marrow transplantation as the treatment of choice for good risk adult patients with acute leukemia. Trans Assoc Am Phys 1979; 92: Santos GW, Tutschka PJ.Effect of busulfan on antibody production and skin allograft survival in the rat. J Natl Cancer Inst 1974; 53: Tutschka PJ, Santos GW.Bone marrow transplantation in the busulfan-treated rat.i.effect of cyclophosphamide and rabbit antirat thymocyte serum as immunosuppression. Transplantation 1975; 20:

8 Tutschka PJ, Santos GW.Bone marrow transplantation in the busulfan-treated rat.ii.effect of cyclophosphamide and antithymic serum on the presensitized state. Transplantation 1975; 20: Tutschka PJ, Santos GW, Elfenbein GJ.Marrow transplantation in acute leukemia following busulfan and cyclophosphamide. Haematol Blood Transfus 1980; 25: Santos GW, Kaizer H.Bone marrow transplantation in acute leukemia. Semin Hematol 1982; 19: Santos GW, Tutschka PJ, Brookmeyer R et al. Marrow transplantation for acute nonlymphocytic leukemia after treatment with busulfan and cyclophosphamide. N Engl J Med 1983; 309: Geller RB, Saral R, Piantadosi S et al. Allogeneic bone marrow transplantation after high-dose busulfan and cyclophosphamide in patients with acute nonlymphocytic leukemia. Blood 1989; 73: Tutschka PJ, Copelan EA, Klein JP.Bone marrow transplantation for leukemia following a new busulfan and cyclophosphamide. Blood 1987; 70: Tutschka PJ, Copelan EA, Kapoor N.Replacing total body irradiation with busulfan as conditioning of patients with leukemia for allogeneic marrow transplantation. Transplant Proc 1989; 21: Copelan EA, Biggs JC, Thompson JM et al. Treatment for acute myelocytic leukemia with allogeneic bone marrow transplantation following preparation with BuCy2. Blood 1991; 78: Zapatero A, Martin de Vidales C, Pinar B et al. Prognostic factors affecting leukemia relapse after allogeneic BMT conditioned with cyclophosphamide and fractionated TBI. Bone Marrow Transplant 1996; 18: Blaise D, Maraninchi D, Archimbaud E et al. Allogeneic bone marrow transplantation for acute myeloid leukemia in first remission: a randomized trial of a busulfan-cytoxan vs cytoxan-total body irradiation as preparative : a report from the Group d Etudes de la Greffe de Moelle Osseuse. Blood 1992; 79: Ringden O, Ruutu T, Remberger M et al. A randomized trial comparing busulfan with total body irradiation as conditioning in allogeneic marrow transplant recipients with leukemia: a report from the Nordic Group. Blood 1994; 83: Ringden O, Labopin M, Tura S et al. A comparison of busulphan vs total body irradiation combined with cyclophosphamide as conditioning for autograft or allograft bone marrow transplantation in patients with acute leukaemia. Acute Leukaemia Working Party of the European Group for Blood and Marrow Transplantation (EBMT). Br J Haematol 1996; 93: Litzow MR, Perez WS, Klein JP et al. Comparison of outcome following allogeneic bone marrow transplantation with cyclophosphamide-total body irradiation vs busulphan-cyclophosphamide conditioning s for acute myelogenous leukaemia in first remission. Br J Haematol 2002; 119: Michel G, Gluckman E, Esperou-Bourdeau H et al. Allogeneic bone marrow transplantation for children with acute myeloblastic leukemia in first complete remission: impact of conditioning without total-body irradiation a report from the Societe Francaise de Greffe de Moelle. J Clin Oncol 1994; 12: Frassoni F, Labopin M, Powles R et al. Effect of centre on outcome of bone-marrow transplantation for acute myeloid leukaemia.acute Leukaemia Working Party of the European Group for Blood and Marrow Transplantation. Lancet 2000; 355: Pino y Torres JL, Bross DS, Lam WC et al. Risk factors in interstitial pneumonitis following allogenic bone marrow transplantation. Int J Radiat Oncol Biol Phys 1982; 8: Labar B, Bogdanic V, Nemet D et al. Total body irradiation with or without lung shielding for allogeneic bone marrow transplantation. Bone Marrow Transplant 1992; 9: Simpson DR, Nevill TJ, Shepherd JD et al. High incidence of extramedullary relapse of AML after busulfan/cyclophosphamide conditioning and allogeneic stem cell transplantation. Bone Marrow Transplant 1998; 22: Witherspoon RP, Fisher LD, Schoch G et al. Secondary cancers after bone marrow transplantation for leukemia or aplastic anemia. N Engl J Med 1989; 321: Curtis RE, Rowlings PA, Deeg HJ et al. Solid cancers after bone marrow transplantation. N Engl J Med 1997; 336: Blaise D, Maraninchi D, Michallet M et al. Long-term followup of a randomized trial comparing the combination of cyclophosphamide with total body irradiation or busulfan as conditioning for patients receiving HLA-identical marrow grafts for acute myeloblastic leukemia in first complete remission. Blood 2001; 97: Ringden O, Remberger M, Ruutu T et al. Increased risk of chronic graft-vs-host disease, obstructive bronchiolitis, and alopecia with busulfan vs total body irradiation: long-term results of a randomized trial in allogeneic marrow recipients with leukemia.nordic Group. Blood 1999; 93: Socie G, Clift RA, Blaise D et al. Busulfan plus cyclophosphamide compared with total-body irradiation plus cyclophosphamide before marrow transplantation for myeloid leukemia: long-term follow-up of 4 randomized studies. Blood 2001; 98: Thomas ED, Clift RA, Hersman J et al. Marrow transplantation for acute nonlymphoblastic leukemic in first remission using fractionated or single-dose irradiation. Int J Radiat Oncol Biol Phys 1982; 8: Clift RA, Buckner CD, Appelbaum FR et al. Long-term follow-up of a randomized trial of two irradiation s for patients receiving allogeneic marrow transplants during first remission of acute myeloid leukemia. Blood 1998; 92: Helenglass G, Powles RL, McElwain TJ et al. Melphalan and total body irradiation (TBI) versus cyclophosphamide and TBI as conditioning for allogeneic matched sibling bone marrow transplants for acute myeloblastic leukaemia in first remission. Bone Marrow Transplant 1988; 3: Blume KG, Kopecky KJ, Henslee-Downey JP et al. A prospective randomized comparison of total body irradiation-etoposide vs busulfan-cyclophosphamide as preparatory s for bone marrow transplantation in patients with leukemia who were not in first remission: a Southwest Oncology Group study. Blood 1993; 81: Snyder DS, Chao NJ, Amylon MD et al. Fractionated total body irradiation and high-dose etoposide as a preparatory for bone marrow transplantation for 99 patients with acute leukemia in first complete remission. Blood 1993; 82: Linker CA, Ries CA, Damon LE et al. Autologous bone marrow transplantation for acute myeloid leukemia using busulfan plus etoposide as a preparative. Blood 1993; 81: Spitzer TR, Cottler-Fox M, Torrisi J et al. Escalating doses of etoposide with cyclophosphamide and fractionated total body irradiation or busulfan as conditioning for bone

9 marrow transplantation. Bone Marrow Transplant 1989; 4: Zander AR, Berger C, Kroger N et al. High dose chemotherapy with busulfan, cyclophosphamide, and etoposide as conditioning for allogeneic bone marrow transplantation for patients with acute myeloid leukemia in first complete remission. Clin Cancer Res 1997; 3: Kroger N, Zabelina T, Sonnenberg S et al. Dose-dependent effect of etoposide in combination with busulfan plus cyclophosphamide as conditioning for stem cell transplantation in patients with acute myeloid leukemia. Bone Marrow Transplant 2000; 26: Brown RA, Wolff SN, Fay JW et al. High-dose etoposide, cyclophosphamide, and total body irradiation with allogeneic bone marrow transplantation for patients with acute myeloid leukemia in untreated first relapse: a study by the North American Marrow Transplant Group. Blood 1995; 85: Bibawi S, Abi-Said D, Fayad L et al. Thiotepa, busulfan, and cyclophosphamide as a preparative for allogeneic transplantation for advanced myelodysplastic syndrome and acute myelogenous leukemia. Am J Hematol 2001; 67: Ratanatharathorn V, Karanes C, Lum LG et al. Allogeneic bone marrow transplantation in high-risk myeloid disorders using busulfan, cytosine arabinoside and cyclophosphamide (BAC). Bone Marrow Transplant 1992; 9: Crilley P, Topolsky D, Styler MJ et al. Extramedullary toxicity of a conditioning containing busulphan, cyclophosphamide and etoposide in 84 patients undergoing autologous and allogenic bone marrow transplantation. Bone Marrow Transplant 1995; 15: Reske SN, Bunjes D, Buchmann I et al. Targeted bone marrow irradiation in the conditioning of high-risk leukaemia prior to stem cell transplantation. Eur J Nucl Med 2001; 28: Jurcic JG, Caron PC, Nikula TK et al. Radiolabeled anti- CD33 monoclonal antibody M195 for myeloid leukemias. Cancer Res 1995; 55: 5908s 5910s. 56 Matthews DC, Appelbaum FR, Eary JF et al. Development of a marrow transplant for acute leukemia using targeted hematopoietic irradiation delivered by 131I-labeled anti-cd45 antibody, combined with cyclophosphamide and total body irradiation. Blood 1995; 85: Matthews DC, Appelbaum FR, Eary JF et al. Phase I study of (131)I-anti-CD45 antibody plus cyclophosphamide and total body irradiation for advanced acute leukemia and myelodysplastic syndrome. Blood 1999; 94: Bunjes D, Buchmann I, Duncker C et al. Rhenium 188-labeled anti-cd66 (a, b, c, e) monoclonal antibody to intensify the conditioning prior to stem cell transplantation for patients with high-risk acute myeloid leukemia or myelodysplastic syndrome: results of a phase I II study. Blood 2001; 98: Jurcic JG, Larson SM, Sgouros G et al. Targeted alpha particle immunotherapy for myeloid leukemia. Blood 2002; 100: Slattery JT, Sanders JE, Buckner CD et al. Graft-rejection and toxicity following bone marrow transplantation in relation to busulfan pharmacokinetics. Bone Marrow Transplant 1995; 16: Vassal G, Deroussent A, Hartmann O et al. Dose-dependent neurotoxicity of high-dose busulfan in children: a clinical and pharmacological study. Cancer Res 1990; 50: Dix SP, Wingard JR, Mullins RE et al. Association of busulfan area under the curve with veno-occlusive disease following BMT. Bone Marrow Transplant 1996; 17: Ljungman P, Hassan M, Bekassy AN et al. High busulfan concentrations are associated with increased transplant-related mortality in allogeneic bone marrow transplant patients. Bone Marrow Transplant 1997; 20: Chattergoon DS, Saunders EF, Klein J et al. An improved limited sampling method for individualised busulphan dosing in bone marrow transplantation in children. Bone Marrow Transplant 1997; 20: Schuler U, Schroer S, Kuhnle A et al. Busulfan pharmacokinetics in bone marrow transplant patients: is drug monitoring warranted? Bone Marrow Transplant 1994; 14: McDonald GB, Slattery JT, Bouvier ME et al. Cyclophosphamide metabolism, liver toxicity, and mortality following hematopoietic stem cell transplantation. Blood 2003; 101: Andersson BS, Madden T, Tran HT et al. Acute safety and pharmacokinetics of intravenous busulfan when used with oral busulfan and cyclophosphamide as pretransplantation conditioning therapy: a phase I study. Biol Blood Marrow Transplant 2000; 6: Olavarria E, Hassan M, Eades A et al. A phase I/II study of multiple-dose intravenous busulfan as myeloablation prior to stem cell transplantation. Leukemia 2000; 14: Schuler US, Renner UD, Kroschinsky F et al. Intravenous busulphan for conditioning before autologous or allogeneic human blood stem cell transplantation. Br J Haematol 2001; 114: Hassan M, Nilsson C, Hassan Z et al. A phase II trial of liposomal busulphan as an intravenous myeloablative agent prior to stem cell transplantation: 500 mg/m(2) as a optimal total dose for conditioning. Bone Marrow Transplant 2002; 30: Kashyap A, Wingard J, Cagnoni P et al. Intravenous vs oral busulfan as part of a busulfan/cyclophosphamide preparative for allogeneic hematopoietic stem cell transplantation: decreased incidence of hepatic venoocclusive disease (HVOD), HVOD-related mortality, and overall 100-day mortality. Biol Blood Marrow Transplant 2002; 8: Russell JA, Tran HT, Quinlan D et al. Once-daily intravenous busulfan given with fludarabine as conditioning for allogeneic stem cell transplantation: study of pharmacokinetics and early clinical outcomes. Biol Blood Marrow Transplant 2002; 8: Ho VT, Soiffer RJ.The history and future of T-cell depletion as graft-versus-host disease prophylaxis for allogeneic hematopoietic stem cell transplantation. Blood 2001; 98: Young JW, Papadopoulos EB, Cunningham I et al. T-celldepleted allogeneic bone marrow transplantation in adults with acute nonlymphocytic leukemia in first remission. Blood 1992; 79: Soiffer RJ, Fairclough D, Robertson M et al. CD6-depleted allogeneic bone marrow transplantation for acute leukemia in first complete remission. Blood 1997; 89: Papadopoulos EB, Carabasi MH, Castro-Malaspina H et al. T-cell-depleted allogeneic bone marrow transplantation as postremission therapy for acute myelogenous leukemia: freedom from relapse in the absence of graft-versus-host disease. Blood 1998; 91: Marmont AM, Horowitz MM, Gale RP et al. T-cell depletion of HLA-identical transplants in leukemia. Blood 1991; 78: Aversa F, Terenzi A, Carotti A et al. Improved outcome with T-cell-depleted bone marrow transplantation for acute leukemia. J Clin Oncol 1999; 17: Maris M, Woolfrey A, McSweeney PA et al. Nonmyeloablative hematopoietic stem cell transplantation: transplantation for the 21st century. Front Biosci 2001; 6: G13 G McSweeney PA, Niederwieser D, Shizuru JA et al. Hematopoietic cell transplantation in older patients with hematologic 977

10 978 malignancies: replacing high-dose cytotoxic therapy with graftvs-tumor effects. Blood 2001; 97: Devine SM, Sanborn R, Jessop E et al. Fludarabine and melphalan-based conditioning for patients with advanced hematological malignancies relapsing after a previous hematopoietic stem cell transplant. Bone Marrow Transplant 2001; 28: Pawson R, Potter MN, Theocharous P et al. Treatment of relapse after allogeneic bone marrow transplantation with reduced intensity conditioning (FLAG +/ Ida) and second allogeneic stem cell transplant. Br J Haematol 2001; 115: Martino R, Caballero MD, Simon JA et al. Evidence for a graft-vs-leukemia effect after allogeneic peripheral blood stem cell transplantation with reduced-intensity conditioning in acute myelogenous leukemia and myelodysplastic syndromes. Blood 2002; 100: Feinstein LC, Sandmaier BM, Hegenbart U et al. Nonmyeloablative allografting from human leucocyte antigenidentical sibling donors for treatment of acute myeloid leukaemia in first complete remission. Br J Haematol 2003; 120: Djulbegovic B, Seidenfeld J, Bonnell C et al.nonmyeloablative allogeneic stem-cell transplantation for hematologic malignancies: a systematic review. Cancer Control 2003; 10: Mielcarek M, Martin PJ, Leisenring W et al. Graft-versus-host disease after nonmyeloablative vs conventional hematopoietic stem cell transplantation. Blood 2003; 102: