Hematopoietic stem-cell transplantation from unrelated ... - Nature

Leukemia (2005) 19, 7–12 & 2005 Nature Publishing Group All rights reserved 0887-6924/05 $30.00 www.nature.com/leu

Hematopoietic stem-cell transplantation from unrelated donors in elderly patients (age455 years) with hematologic malignancies: older age is no longer a contraindication when using reduced intensity conditioning A Shimoni1, N Kro¨ger2, T Zabelina2, F Ayuk2, I Hardan1, M Yeshurun1, N Shem-Tov1, A Avigdor1, I Ben-Bassat1, AR Zander2 and A Nagler1 1

The Division of Hematology and Bone Marrow Transplantation, Chaim Sheba Medical Center, Tel-Hashomer, Israel; and 2The Department of Bone Marrow Transplantation, Hamburg University Hospital, Hamburg, Germany

Allogeneic stem cell transplantation (SCT) is a potentially curative approach for patients with hematological malignancies. Reduced-intensity conditioning regimens allow SCT in elderly patients; however, there are only limited data on the feasibility and outcomes of unrelated donor SCT in these patients. In this study, we analyzed, retrospectively, data of 36 patients with various hematological malignancies and median age 58 years (range, 55–66), who were given unrelated donor SCT after reduced-intensity conditioning. The preparative regimen consisted of fludarabine combined with oral busulfan (8 mg/kg, n ¼ 8), intravenous busulfan (6.4 mg/kg, n ¼ 11), treosulfan (30 g/m2, n ¼ 5) or melphalan (100–150 mg/m2, n ¼ 12). Patients were also given serotherapy, ATG (n ¼ 32), or alemtuzumab (n ¼ 4). The probabilities of overall survival, disease-free survival, and nonrelapse mortality at 1 year after SCT were 52, 43, and 39%, respectively. Acute graft-versus-host disease (GVHD) grade II–IV and chronic GVHD occurred in 31 and 45%, respectively. Multivariable analysis determined that survival rates were higher in patients with chemosensitive disease (HR 4.5), and patients conditioned with intravenous busulfan or treosulfan (HR 3.9). Unrelated donor SCT is feasible in elderly patients, with outcomes that are similar to younger patients. Favorable outcome was observed in patients with myeloid malignancies, and those transplanted in remission and early in the course of disease. Age alone should not be considered a contraindication to unrelated donor SCT. Leukemia (2005) 19, 7–12. doi:10.1038/sj.leu.2403591 Published online 4 November 2004 Keywords: stem cell transplantation; matched unrelated donor; nonmyeloablative; reduced intensity

Introduction Allogeneic hematopoietic stem cell transplantation (SCT) is an effective, potentially curative treatment of advanced or high-risk hematological malignancies.1 However, it is associated with significant morbidity and mortality due to the toxicity of the preparative regimen, graft-versus-host disease (GVHD), and the immune deficiency state that accompanies the procedure. These risks are significantly increased with advanced age and concurrent medical problems limiting standard SCT to younger patients in good medical condition. Treatmentrelated complications are even more frequent after SCT from unrelated donors, and thus most centers limit unrelated donor SCT to patients younger than 50–55 years.2–7 Hematological malignancies are more common and have a worse prognosis in the elderly and age, disease, or therapy-related comorbidities might preclude further intensive therapy. The elderly are Correspondence: Dr A Shimoni, Department of Bone Marrow Transplantation, Chaim Sheba Medical Center, Tel-Hashomer, Israel; Fax: þ 972 3 530 5377; E-mail: [email protected] Received 2 June 2004; accepted 9 August 2004; Published online 4 November 2004

also less likely to have a living healthy HLA-matched sibling able to donate stem cells for SCT. Thus, many patients with hematological malignancies who could benefit from SCT were often deferred from potentially curative approach. The introduction of nonmyeloablative stem cell transplantation (NST) allowed extension of allogeneic SCT to a much wider patient population including the elderly, by reducing toxicity and exploiting the graft-versus-leukemia (GVL) effect as the curative approach.8–11 Much experience has already been gained with the clinical use of this approach in the HLAmatched sibling setting; however, there are only limited data on the feasibility, and outcome of unrelated donor SCT in elderly patients over age 55 years.12 In this retrospective study, we report our experience with 36 patients with various hematologic malignancies having unrelated donor SCT following reducedintensity conditioning.

Patients and methods

Patient eligibility This study included patients aged 55 years and above with an unrelated donor available for SCT. Patients were eligible for this study if they had any hematologic malignancy at high risk for relapse. Patients with acute leukemia could be at first remission but at high risk for relapse due to adverse cytogenetical abnormalities, prior hematological disorder, excessive blast count at presentation (4100 109/l) or slow response to induction therapy (two or more chemotherapy cycles required for remission induction), or at any status beyond first remission. Patients with myelodysplastic syndrome (MDS) had to be at least with excess of blasts but could be previously untreated. Patients with chronic myeloid leukemia (CML) had to be resistant to interferon and/or imatinib mesylate or beyond the first chronic phase. Patients were required to be free of marked organ dysfunction and to have an ECOG performance score of 0–2. All patients gave written informed consent and the study was approved by the institution review boards.

Donor selection Donors were selected based on serologic typing of A and B antigens, and high-resolution typing of DR antigens. Donors and recipients could be complete matched or mismatched at one antigen based on these criteria. For some donor–recipient pairs (n ¼ 12), high-resolution typing of Class I antigens was also available. Donors were selected trying to allow minimal allelic mismatches and no more than two when possible. Donors’ work-up was according to donor center guidelines. Donors

Unrelated donor SCT in the elderly A Shimoni et al

8 could donate either bone marrow or G-CSF mobilized peripheral blood stem cells.

Results

Patient characteristics Conditioning regimen All patients were given reduced-intensity conditioning based on fludarabine 125–180 mg/m2 intravenously combined with oral busulfan (a total of 8 mg/kg, n ¼ 8), intravenous busulfan (a total of 6.4 mg/kg, n ¼ 11), intravenous treosulfan (30 g/m2, n ¼ 5), or melphalan (100–150 mg/m2, n ¼ 12). The alkylating agent used was selected based on disease type, physician discretion, prior therapy, and/or institutional protocols at the time of SCT. Patients with multiple myeloma were preferentially treated with melphalan, whereas patients with leukemia were preferentially given oral or intravenous busulfan. All patients were given serotherapy in the form of antithymocyte globulin (ATG, Fresenius) at a total dose of 15–90 mg/kg (n ¼ 32) or alemtuzumab at a total dose of 80 mg (n ¼ 4). Phenytoin was administered before and until 24 h after completion of busulfan. Prophylaxis against GVHD consisted of cyclosporin A and a short course of methotrexate (15 mg/m2 on day 1 and 10 mg/m2 on days 3 and 6). Patients given alemtuzumab were given cyclosporine alone. G-CSF was administered routinely from day þ 4 until engraftment. The standard institutional regimen of antibiotics was employed for the prevention of bacterial, viral, fungal, and pneumocystis infections.

Evaluation of response Neutrophil and platelet engraftment were defined as the first of 3 days with absolute neutrophil count (ANC) 40.5 109/l and the first of 7 days with an untransfused platelet count 420 109/l, respectively. Toxicity post-transplantation was graded by the Bearman scale.13 Acute and chronic GVHD were graded and staged by standard criteria. Chimerism was tested using FISH with X and Y chromosome probes in sex-mismatched transplants and with PCR analysis of microsatellite markers in sexmatched transplants.14 Response and relapse were determined by standard hematologic criteria. Cytogenetic and molecular markers were used when applicable but were not used for determination of disease status.

A total of 36 patients with various hematological malignancies were included in the study. The median age was 58 years (range, 55–66), 20 males and 16 females. In all, 10 patients were aged 60 years and above. Of these, 15 patients had AML (in 10 patients AML was secondary to prior MDS or prior therapy), four had MDS, three had CML, two had myelofibrosis, eight had multiple myeloma, and four had non-Hodgkin’s lymphoma. The disease characteristics and status at transplantation are outlined in Table 1. In all, 15 patients had a prior autologous SCT and allogeneic SCT was given for treatment of post-SCT relapse (n ¼ 12), secondary leukemia (n ¼ 1), or on an auto/allo program (n ¼ 2). A total of 28 patients had a malignancy that either had at least partial response to prior chemotherapy (n ¼ 22) or were previously untreated (n ¼ 6), and eight patients had chemorefractory malignancy.

Donor characteristics A total of 31 donor recipient pairs were 6/6 HLA-matched by the above criteria. Five pairs were HLA mismatched; three had allelic mismatch at DR and two had antigen mismatch at the A locus. High-resolution class 1 typing was available for 12 of the matched pairs. Four of the pairs considered complete matches by the standard criteria had a single allelic mismatch. The allograft source was peripheral blood stem cells (n ¼ 31) or bone marrow (n ¼ 5).

Engraftment A total of 32 patients engrafted. The median time to ANC 0.5 109/l was 14 days (range, 8–25 days). The median time to platelet 20 109/l was 17 days (range, 10–111 days, four patients did not achieve platelet transfusion independency).

Table 1

Disease characteristics at SCT

Disease

Number

Disease status at SCT

Myeloid (n ¼ 24)

AML 15

CR1 5 CR2 7 Refractory 3 Previously untreated 4 Chronic phase 1 Advanced 2 Previously untreated 2

Statistical analysis Overall survival (OS) was calculated from the day of transplantation until death of any cause or last follow-up. Disease-free survival (DFS) was calculated from the day of transplantation until relapse or death of any cause or last follow-up. The probabilities of survival and disease-free survival were estimated and plotted using the Kaplan–Meier method.15 Relapse and nonrelapse mortality rates were estimated using cumulative incidence analysis and were considered as competing risks. Similarly, in the analysis of GVHD rates, death due to other causes or relapse leading to early withdrawal of immune suppression were considered as competing risk. The effect of various patient and disease categorical variables on survival probabilities was studied with the log-rank test. A Cox proportional hazard model with limited variables due to small sample was used to determine the significance of multiple variables in determining these outcomes. Leukemia

MDSa 4 CML 3 AMM 2 Lymphoid (n ¼ 12)

MMb 8 c

NHL 4

PR PD PR PD

5 3 2 2

AML, acute myeloid leukemia; MDS, myelodysplastic syndromes; CML, chronic myeloid leukemia; AMM, agnogeneic myeloid metaplasia with myelofibrosis; MM, multiple myeloma; NHL, non-Hodgkin’s lymphoma; CR, complete remission; PR, partial response; PD, progressive disease. SCT, stem cell transplantation; auto, autologous; allo, allogeneic. a All these patients were with excess blasts or in transformation. b All patients had a prior autologous SCT, six have relapsed after autologous SCT and two patients were treated on an auto/mini-allo program. c All patients relapsed after a prior autologous SCT.


9 occurred in two patients, grade III renal toxicity occurred in three patients, and CNS toxicity in two patients (some patients had grade III–IV toxicity in more than one system). Grade II–IV and III–IV acute GVHD occurred in 11 (31%) and four (11%) patients, respectively. The cumulative incidence is 28% (95% Confidence Interval (CI) 16–49%) and 14% (95% CI 5–35%), respectively. Chronic GVHD occurred in nine of 20 evaluable patients (45%). Overall, nonrelapse mortality (NRM) occurred in 13 patients with a cumulative incidence of 39% (95% CI 26–60%) at 1 year after SCT. Eight patients died of direct regimen-related organ toxicities, three died of complications related to acute GVHD, and two from infections. The most significant factor predicting of NRM was the type of conditioning used prior to SCT (Tables 2 and 3, Figure 2). In all, 11 of 20 patients treated with the old generation regimens containing melphalan or oral busulfan died of NRM in comparison with only two of 16 given the new generation regimens containing intravenous busulfan or treosulfan (P ¼ 0.02). This difference is even more striking when comparing only deaths related to organ

Four patients died before engraftment. At the time of first testing after engraftment, 17 patients had complete donor chimerism and seven had mixed chimerism, ranging from 60 to 98% donor. Data are not available for 12 patients, six have died prior to testing, one had persistent leukemia, and five were not tested for other reasons. Six of the seven patients with mixed chimerism converted spontaneously to complete chimerism, and one has so far remained a mixed chimera. The median time to detection of complete chimerism was 29 days (range 15–58).

Toxicity and GVHD Grade III–IV organ toxicity by the Bearman criteria occurred in 11 patients (31%) and was directly related to eight deaths. Three patients died of grade IV liver toxicity, and two of pulmonary toxicity (diffuse alveolar hemorrhage). In two patients, the major cause of death was thrombotic microangiopathy and heart failure resulted in one death. Additionally, grade III mucositis

Table 2

Clinical characteristics in relation to OS, DFS, and NRM after SCTa

Variable

n

Total Age (years) X60 o60 Gender Male Female Disease Myeloid Lymphoid Prior auto Yes No Chemosens Yes No HLA Matched mm Cond. i.v. Bu/Treo oral Bu/M

OS Alive

OS (%)

36

20

5279

12 24

8 12

60717 46711

20 16

28 2

24 12

DFS P

Dis-free

DFS (%)

17

4379

NS

6 11

40720 42711

40712 67712

NS

8 9

15 5

57711 42714

NS

15 21

6 14

40713 61712

28 8

18 2

31 5 16 20

NRM P

Died NRM

NRM (%)

P

13

3979

NS

4 9

40718 40710

NS

32712 59712

NS

9 4

48712 26711

NS

14 3

57711 22713

NS

7 6

33711 50714

NS

NS

4 13

25712 61712

0.08

7 6

47713 34712

NS

61710 16714

0.04

15 2

50711 16714

0.03

9 4

31718 53719

NS

18 2

5579 40722

NS

15 2

45710 40722

NS

10 3

3479 60722

NS

12 8

66715 40711

0.06

12 5

66715 29710

0.03

2 11

19713 55711

0.02

a

Survival rates estimated by the Kaplan–Meier method and categorical values compared with log-rank test. NRM was estimated using cumulative incidence analysis with relapse considered competing risk. Results are given with 7standard error. OS, overall survival; DFS, disease-free survival; NRM, non-relapse mortality; chemosens; chemosensitive or previously untreated; HLA, donor– recipient matching (see text); mm, mismatched; cond., conditioning regimen; i.v. Bu/Treo, fludarabine combined with intravenous busulfan or treosulfan; oral Bu/M, fludarabine combined with oral busulfan or intravenous melphalan; NS, nonsignificant.

Table 3

Proportional hazards regression model for survival, DFS and TRM after SCTa

Variable

Disease type (lymhoid) Cond. (oral Bu/M) Chemosen

Overall survival

DFS

NRM

Hazard ratio (95% CI)

P


P


P

2.3 (0.7–8.1) 3.9 (1.2–13.3) 4.5 (1.3–15.5)

NS 0.03 0.02

1.6 (0.5–4.8) 3.9 (1.2–12.6) 3.6 (1.0–12.2)

NS 0.03 0.04

2.8 (0.7–11.1) 6.3 (1.3–30.5) 1.9 (0.5–7.2)

NS 0.02 NS

a

Factors evaluated in the univariable analysis (Table 2) were included in a limited Cox regression model. Hazard ratios for reduced survival or increased TRM of categorical variable are given in parentheses. Abbreviations as in Table 2. Leukemia


10 toxicities reaching a cumulative incidence of 35 and 6%, respectively (P ¼ 0.04).

Outcome With a median follow-up of 10 months (range, 1–54), 20 patients are alive and 16 have died. Of these, 13 patients died of treatment-related complications and three of disease relapse. The actuarial 1-year OS is 52% (95% CI 34–69%) (Figure 1). A total of 17 patients remain alive and disease-free. Six patients have relapsed, three with AML and three with multiple myeloma. The cumulative incidence of relapse is 28% (95% CI 12–62%). Two patients with AML died shortly after relapse. One of these patients is alive in remission 22 months after a second SCT. Two of the three patients with myeloma were given DLI but did not respond. One died and two are alive but not in complete remission and are given other therapies. Overall, the actuarial 1-year DFS is 43% (95% CI 24–62%). Five patients are currently alive more than 20 months from SCT. Three are still disease-free; one is the patient alive and disease-free 22 months after a second allogeneic SCT. The fifth is been treated for disease recurrence. Table 2 outlines the univariable analysis of factors influencing outcome. The status of disease at SCT and the conditioning regimen used were the most significant predictors of outcome. Patients with chemosensitive or previously untreated malignancy had an OS of 61% (95% CI 42–80%), whereas patients with refractory malignancy had an OS of 16% (95% CI 0–43%). Patients conditioned with fludarabine and intravenous busulfan or treosulfan had a better outcome than those conditioned with fludarabine and oral busulfan or intravenous melphalan (Figure 3). This is mostly related to increased nonrelapse mortality with the later regimens (Figure 2). A limited multivariable analysis confirmed the independent impact of these factors (Table 3) with hazard ratios for decreases OS of 4.5 and 3.9, respectively. When a more homogenous subgroup of 19 patients with AML or MDS was analyzed, the 1-year OS and DFS was 55% (95% CI 28–82%) and NRM was 32% (95% CI 15–71%). The same factors predicted outcomes although with only borderline statistical significance due to the lower number of patients (data not shown).

Figure 2 Comparison of the cumulative incidence of NRM rates after unrelated donor SCT using different reduced-intensity regimens. NRM is higher when oral busulfan or intravenous melphalan are used than when intravenous busulfan or treosulfan are used as alkylating agents in addition to fludarabine during conditioning.

Figure 3 Comparison of OS rates after unrelated donor SCT using different reduced-intensity regimens. Survival rates are higher when intravenous busulfan or treosulfan are used than when oral busulfan or intravenous melphalan are used as alkylating agents in addition to fludarabine during conditioning.

Discussion

Figure 1 Kaplan–Meier analysis of overall survival (middle curve) with 95% confidence interval (upper and lower curves) in 36 patients, aged 55–66 years, after unrelated donor SCT with reduced-intensity conditioning. Leukemia

This study shows the feasibility of unrelated donor SCT in elderly patients, age 55–66 years, who until recently were not considered good candidates for SCT, in particular with donors other than HLA-matched siblings. Outcome after unrelated donor SCT has been inferior to SCT from HLA-matched siblings despite some compensation offered by better GVL for increased treatment-related mortality (TRM). Recent advances in SCT such as better supportive care modalities (eg in GVHD and infection control), larger donor registries, and improved tissue typing techniques for selection of unrelated donors,16 and introduction of new chemotherapeutic agents such as intravenous busulfan17 and treosulfan18 have made this treatment much safer with outcomes that in younger patients are now approaching those of matched-sibling SCT. Low-intensity conditioning has been


11 shown to be sufficient to ensure engraftment in the unrelated setting and reduce toxicity, and elderly patients have been included in such studies.19–22 It is now established that patient performance and comorbidity score are more important than age per se in predicting the ability to tolerate intensive therapies.23,24 This study supports the notion that patients should not be deferred from potentially curative therapy based on age alone, as outcomes were not significantly different from that expected in similar settings at a younger age. The patients included in this study had underlying malignancies that were predictive of a short survival, mostly secondary leukemias and relapsing malignancies after a prior autologous SCT. The median follow-up of patients in this study is relatively short and care should be taken when predicting long-term outcome. However, the predicted 1-year survival of 52% in this setting seems encouraging, and similar to that reported in younger patients. Favorable outcome was seen mostly in patients with myeloid malignancies, especially when in remission at the time of SCT. Acute leukemia in the elderly is often secondary to prior MDS, and carries poor prognosis. Among 19 patients with AML and MDS (only five with de novo AML) included in this study, 1-year OS, DFS, and NRM were 55, 55, and 32%, respectively. The MD Anderson group reported in a series of 29 patients over age 54 years with myeloid malignancies that the probabilities were 44, 37, and 55% at 1year post-SCT, respectively.25 Similarly, Bertz et al26 reported that 10 of 12 elderly patients with high-risk leukemia survived after SCT from unrelated donors given relatively early in the disease course. These results compare favorably with those reported by the EBMT3 and NMDP.4 The OS of 198 patients with MDS and secondary AML after unrelated donor SCT reported to EBMT was 25%, and only 11% in patients over the age of 40 years, mostly related to excessive TRM rates of 58, and 73%, respectively.3 Selected patients with lymphoma and myeloma also fared from unrelated donor SCT, but with a lower chance for prolonged DFS. This can be related to a less effective graft versus malignancy effect in these diseases. However another important consideration is that patients with leukemia more often had SCT earlier in the course of disease, whereas patients with lymphoma and myeloma were only considered for unrelated donor SCT after failure of a prior autologous SCT, when they had advanced disease and been heavily pretreated, and susceptible to both higher TRM, and a lesser opportunity for disease control. Therefore, unrelated donor SCT needs to be considered early in selected groups of patients. An auto/miniallo approach can combine the advantages of high-dose chemotherapy, and GVM, early in the disease course, and was evaluated mostly in patients with multiple myeloma (including two patients in this study).27 TRM rates were still high in this study with a cumulative 1year incidence of 39%. Similarly, the MD Anderson study reported TRM rates of 55%.24 Reduced-intensity conditioning did not reduce TRM markedly but rather made unrelated donor SCT feasible. However, considering the very poor outcome expected without SCT these TRM rates may be considered acceptable. In contrast, the Seattle group, using a regimen consisting of low dose total body irradiation with fludarabine and intensive pre- and post-transplant immunosuppression for unrelated donor SCT in 89 patients (median age 53 years), reported 1-year TRM of only 16%.20 The differences relate to the use of different dose intensities. NST regimens comprise of a spectrum of regimens with different immunosuppressive and myelosuppressive properties.8 Conditioning regimens have been referred to as nonmyeloablative if they do not completely

eradicate host hematopoiesis and immunity and commonly result in induction of mixed chimerism. The Seattle regimen is the prototype of these regimens.11 Reduced-intensity regimens, like those used in this study, are more intensive and myelosuppressive. They rapidly induce complete chimerism and allogeneic responses. They are more toxic than the nonmyeloablative regimens and probably associated with a higher risk for acute GVHD.12 However, there are initial suggestions that in aggressive malignancies, such as myeloid leukemias, better cytoreduction, as that offered by the reducedintensity regimens may be needed for transient disease control prior to induction of GVL. Recurrence rate may be lower, translating to better DFS despite the larger TRM rate.28 Reducedintensity regimens may also be required in patients not given prior chemotherapy, such as those with CML or previously untreated MDS, who may have a high risk of graft rejection with nonmyeloablative regimens.20 Most of the NRM deaths in this study were related to organ toxicity with a relative low incidence of GVHD. This may be related to the use of ATG in the conditioning in most patients29 and alemtuzumab22 in some patients and to the limitation of tissue injury, which is involved in the pathogenesis of acute GVHD by the use of reduced-intensity conditioning.12 The susceptibility of older patients to organ toxicity may have competed with the incidence of GVHD, or its diagnosis. We observed encouraging results with some of the regimens used. The cumulative incidence of NRM was only 19% in patients conditioned with intravenous busulfan or treosulfan, compared to 55% in those conditioned with melphalan or oral busulfan, despite similar dose intensities. TRM associated with these new reduced-intensity regimens was similar to that observed with nonmyeloablative regimens, and translated to better survival rates. Elderly patients may be extremely susceptible to the extramedullary toxicity of intensive regimens. Therefore, the advantages of more tolerable chemotherapeutic agents may become significant not only in myeloablative doses17 but also in lower dose intensities. These observations suggest that not all NST regimens are similar, and modifications in regimen composition may have significant influence on outcome. Further studies will be needed to determine the best NST regimen, and different regimens may have better outcomes in different settings, depending on factors such as age, type, aggressiveness, and chemosensitivity of the underlying disease, prior therapy, etc. In conclusion, unrelated donor SCT is feasible in elderly patients, aged 55 years and above, although with a significant NRM rate. Favorable outcome can be observed mostly in patients with myeloid malignancies, and those transplanted in remission and early in the course of disease. Novel regimens need to be explored trying to further reduce toxicity, while preserving the antimalignancy effect. Prospective studies with a larger patient group and longer follow-up are needed to better define the role of unrelated donor SCT in the elderly. However, age alone should no longer be considered a contraindication to such SCT.

References 1 Thomas ED, Storb R, Clift RA, Fefer A, Johnson L, Neiman PE et al. Bone marrow transplantation. N Engl J Med 1975; 292: 832–843. 2 Kernan NA, Bartsch G, Ash RC, Beatty PG, Champlin R, Filipovich A et al. Analysis of 462 transplantations from unrelated donors facilitated by the National Marrow Donor Program. N Engl J Med 1993; 328: 593–602. Leukemia


12 3 de Witte T, Hermans J, Vossen J, Bacigalupo A, Meloni G, Jacobsen N et al. Haematopoietic stem cell transplantation for patients with myelo-dysplastic syndromes and secondary acute myeloid leukaemias: a report on behalf of the Chronic Leukaemia Working Party of the European Group for Blood and Marrow Transplantation (EBMT). Br J Haematol 2000; 110: 620–630. 4 Castro-Malaspina H, Harris RE, Gajewski J, Ramsay N, Collins R, Dharan B et al. Unrelated donor marrow transplantation for myelodysplastic syndromes: outcome analysis in 510 transplants facilitated by the National Marrow Donor Program. Blood 2002; 99: 1943–1951. 5 Cornelissen JJ, Carston M, Kollman C, King R, Dekker AW, Lowenberg B et al. Unrelated marrow transplantation for adult patients with poor-risk acute lymphoblastic leukemia: strong graftversus-leukemia effect and risk factors determining outcome. Blood 2001; 97: 1572–1577. 6 Sierra J, Storer B, Hansen JA, Martin PJ, Petersdorf EW, Woolfrey A et al. Unrelated donor marrow transplantation for acute myeloid leukemia: an update of the Seattle experience. Bone Marrow Transplant 2000; 26: 397–404. 7 McGlave PB, Shu XO, Wen W, Anasetti C, Nademanee A, Champlin R et al. Unrelated donor marrow transplantation for chronic myelogenous leukemia: 9 years’ experience of the national marrow donor program. Blood 2000; 95: 2219–2225. 8 Champlin R, Khouri I, Shimoni A, Gajewski J, Kornblau S, Molldrem J et al. Harnessing graft-versus-malignancy: nonmyeloablative preparative regimens for allogeneic haematopoietic transplantation, an evolving strategy for adoptive immunotherapy. Br J Haematol 2000; 111: 18–29. 9 Slavin S, Nagler A, Naparstek E, Kapelushnik Y, Aker M, Cividalli G et al. Nonmyeloablative stem cell transplantation and cell therapy as an alternative to conventional bone marrow transplantation with lethal cytoreduction for the treatment of malignant and nonmalignant hematologic diseases. Blood 1998; 91: 756–763. 10 Giralt S, Estey E, Albitar M, van Besien K, Rondon G, Anderlini P et al. Engraftment of allogeneic hematopoietic progenitor cells with purine analog-containing chemotherapy: harnessing graftversus-leukemia without myeloablative therapy. Blood 1997; 89: 4531–4536. 11 McSweeney PA, Niederwieser D, Shizuru JA, Sandmaier BM, Molina AJ, Maloney DG et al. Hematopoietic cell transplantation in older patients with hematologic malignancies: replacing highdose cytotoxic therapy with graft-versus-tumor effects. Blood 2001; 97: 3390–3400. 12 Shimoni A, Nagler A. Nonmyeloablative stem-cell transplantation: lessons from the first decade of clinical experience. Curr Hematol Rep 2004; 3: 242–248. 13 Bearman SI, Appelbaum FR, Buckner CD, Petersen FB, Fisher LD, Clift RA et al. Regimen-related toxicity in patients undergoing bone marrow transplantation. J Clin Oncol 1988; 6: 1562–1568. 14 Shimoni A, Nagler A. Non-myeloablative stem cell transplantation (NST): chimerism testing as guidance for immune-therapeutic manipulations. Leukemia 2001; 15: 1967–1975. 15 Kaplan EL, Meier P. Nonparametric estimation from incomplete observations. J Am Stat Assoc 1958; 53: 457–481. 16 Petersdorf EW, Gooley TA, Anasetti C, Martin PJ, Smith AG, Mickelson EM et al. Optimizing outcome after unrelated marrow transplantation by comprehensive matching of HLA class I and II alleles in the donor and recipient. Blood 1998; 92: 3515–3520. 17 Shimoni A, Bielorai B, Toren A, Hardan I, Avigdor A, Yeshurun M et al. Intravenous busulfan-based conditioning prior to allogeneic

Leukemia

18

19

20

21

22

23

24

25

26 27

28

29

hematopoietic stem cell transplantation: myeloablation with reduced toxicity. Exp Hematol 2003; 31: 428–434. Casper J, Knauf W, Kiefer T, Wolff D, Steiner B, Hammer U et al. Treosulfan and fludarabine: a new toxicity-reduced conditioning regimen for allogeneic hematopoietic stem cell transplantation. Blood 2004; 103: 725–731. Nagler A, Aker M, Or R, Naparstek E, Varadi G, Brautbar C et al. Low-intensity conditioning is sufficient to ensure engraftment in matched unrelated bone marrow transplantation. Exp Hematol 2001; 29: 362–370. Maris MB, Niederwieser D, Sandmaier BM, Storer B, Stuart M, Maloney D et al. HLA-matched unrelated donor hematopoietic cell transplantation after nonmyeloablative conditioning for patients with hematologic malignancies. Blood 2003; 102: 2021–2030. Giralt S, Thall PF, Khouri I, Wang X, Braunschweig I, Ippolitti C et al. Melphalan and purine analog-containing preparative regimens: reduced-intensity conditioning for patients with hematologic malignancies undergoing allogeneic progenitor cell transplantation. Blood 2001; 97: 631–637. Chakraverty R, Peggs K, Chopra R, Milligan DW, Kottaridis PD, Verfuerth S et al. Limiting transplantation-related mortality following unrelated donor stem cell transplantation by using a nonmyeloablative conditioning regimen. Blood 2002; 99: 1071–1078. Diaconescu R, Flowers CR, Storer B, Sorror ML, Maris MB, Maloney DG et al. Morbidity and mortality with nonmyeloablative compared to myeloablative conditioning before hematopoietic cell transplantation from HLA matched related donors. Blood 2004; 104: 1550–1558. Sorror ML, Maris MB, Storer B, Sandmaier BM, Diaconescu R, Flowers C et al. Comparing morbidity and mortality of HLA-matched unrelated donor hematopoietic cell transplantation after nonmyeloablative and myeloablative conditioning: Influence of pretransplant comorbidities. Blood 2004; 104: 961–968. Wong R, Giralt SA, Martin T, Couriel DR, Anagnostopoulos A, Hosing C et al. Reduced-intensity conditioning for unrelated donor hematopoietic stem cell transplantation as treatment for myeloid malignancies in patients older than 55 years. Blood 2003; 102: 3052–3059. Bertz H, Potthoff K, Finke J. Allogeneic stem-cell transplantation from related and unrelated donors in older patients with myeloid leukemia. J Clin Oncol 2003; 21: 1480–1484. Kroger N, Schwerdtfeger R, Kiehl M, Sayer HG, Renges H, Zabelina T et al. Autologous stem cell transplantation followed by a dose-reduced allograft induces high complete remission rate in multiple myeloma. Blood 2002; 100: 755–760. De Lima M, Anagnostopoulos A, Munsell M, Shahjahan M, Ueno N, Ippoliti C et al. Non-ablative versus reduced intensity conditioning regimens in the treatment of acute myeloid leukemia and high-risk myelodysplastic syndrome. Dose is relevant for long-term disease control after allogeneic hematopoietic stem cell transplantation. Blood 2004; 104: 865–872. Zander AR, Kroger N, Schleuning M, Finke J, Zabelina T, Beelen D et al. ATG as part of the conditioning regimen reduces transplantrelated mortality (TRM) and improves overall survival after unrelated stem cell transplantation in patients with chronic myelogenous leukemia (CML). Bone Marrow Transplant 2003; 32: 355–361.