J Clin Oncol 24: by American Society of Clinical Oncology INTRODUCTION

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1 VOLUME 24 NUMBER 24 AUGUST JOURNAL OF CLINICAL ONCOLOGY O R I G I N A L R E P O R T Results of Genoidentical Hemopoietic Stem Cell Transplantation With Reduced Intensity Conditioning for Acute Myelocytic Leukemia: Higher Doses of Stem Cells Infused Benefit Patients Receiving Transplants in Second Remission or Beyond The Acute Leukemia Working Party of the European Cooperative Group for Blood and Marrow Transplantation Norbert-Claude Gorin, Myriam Labopin, Jean-Michel Boiron, Niklas Theorin, Tim Littlewood, Shimon Slavin, Hildegard Greinix, Jean Yves Cahn, E. Paolo Alessandrino, Alessandro Rambaldi, Arnon Nagler, Emmanuelle Polge, and Vanderson Rocha From the Department of Haematology and Cell Therapy; the European Group for Blood and Marrow Transplantation Acute Leukemia Working Party, Hopital Saint-Antoine Asistance Publique Hopitaux de Paris and Université Paris 6, Pierre et Marie Curie; Department of Hematology, Hopital Saint-Louis Asistance Publique Hopitaux de Paris and Uniersité Paris, Paris; Centre Hospitalo Universitaire Bordeaux, Hôpital Hautleveque, Pessac; Hopital A. Michallon, Department of Oncology-Hematology and Université Joseph Fourier, Grenoble, France; University Hospital, Department of Hematology, Linköping, Sweden; The Oxford Radcliffe Hospital, Clinical Haematology, Oxford, United Kingdom; Hadassah University Hospital, Department of Bone Marrow Transplantation, Jerusalem; Tel-Aviv University, Chaim Sheba Medical Center, Tel-Hashomer, Israel; Medizinische Universitaet Wien, Klinik fuer Innere Medizin I, Vienna, Austria; Policlinico San Matteo, Department of Hematology, Bone Marrow Transplantation unit, Institute for Research Against Cancers, Pavia; and the Ospedale Bergamo, Divisione di Ematologia, Bergamo, Italy. Submitted January 9, 2006; accepted June 19, 2006; published online ahead of print at on July 31, Authors disclosures of potential conflicts of interest and author contributions are found at the end of this article. Address reprint requests to Norbert- Claude Gorin, MD, PhD, Hopital Saint- Antoine, 184 rue du faubourg Saint- Antoine, Paris France; norbert-claude.gorin@sat.aphp.fr by American Society of Clinical Oncology X/06/ /$20.00 DOI: /JCO A B S T R A C T Purpose Nucleated cell dose is an important and modifiable factor in hematopoietic stem cell transplantation (HSCT), however its association with outcomes in the context of reduced intensity conditioning regimen (RIC) HSCT for adults with acute myelocytic leukemia (AML) is not known. Patients and Methods From 1998 to 2003, 253 patients with de novo AML, received transplants with RIC and peripheral blood from a genoidentical donor. Median age was 55 years (range, 18 to 72) and the median follow-up was 17 months (range, 2 to 67). One hundred forty one patients received transplants in first remission (CR1), 47 received transplants in second remission (CR2), and 65 patients received transplants in a more advanced phase. Fludarabin-based RIC was used in 91% of patients and low-dose ( 4 Gy) total-body radiation in 23% of patients. The median nucleated and CD34 cell dose infused were /kg and /kg, respectively. Results Overall, 2-year leukemia-free survival (LFS) was 41% 4% and it was 46% 5% for patients receiving a higher cell dose ( /kg) and 37% 5% for the remainders (P.03). Higher cell doses exclusively benefited patients who received transplantations in CR2 or beyond, with LFS of 47 8 versus 20 8, with no detectable effect for patients who received transplants in CR1. In a multivariate analysis of the overall patient population, higher nucleated cell dose cells were associated with higher LFS (P.04), higher incidence of chronic graft-versus-host disease (P.01), and there was a trend towards a lower relapse incidence (P.06). Interestingly, CD34 cell dose was not associated with any outcomes. Conclusion Nucleated cell dose is an important factor that can be modified to improve results of RIC for patients with AML transplanted later than in CR1. J Clin Oncol 24: by American Society of Clinical Oncology INTRODUCTION Allogeneic stem-cell transplantation following myeloablative regimens, has been widely used to treat patients with acute myelocytic leukemia (AML) since the early 1970s. 1-4 Several prognostic factors are however important for the outcome, age, and physical condition in particular. For patients younger than 35 years of age, a cure for leukemia can be achieved in approximately 60% of patients if the transplant is done in first remission (CR1), 40% of patients in second remission, and still 15% even in more advanced diseases. 5 In contrast, older age is associated with a high (unacceptable) incidence and severity of graft-versushost disease (GVHD) leading to high transplantationrelated mortality (TRM). 6 Following studies in animal models, a new modality nonmyeloablative transplant or reduced intensity conditioning (RIC) has been developed for older patients and patients with a high risk of 3959

2 Gorin et al TRM, 7-16 with the argument that a less intense preparative regimen would produce less organ damage, and still enable engraftment and occurrence of graft-versus-tumor effect. 17 In the past 6 years this approach has proved feasible, and the induction of graft-versus-tumor effect has indeed generated a high rate of responses. However, it remains unclear whether the reduction in antitumor activity secondary to the decrease in intensity of the preparative regimen is compensated by the graft-versus-tumor effect which in this approach is the key antitumor tool. Number of nucleated or CD34 cells infused are important risk factors in the field of hematopoietic stem-cell transplantation independent of the type of donor (autologous or allogeneic, human leukocyte antigen [HLA] identical sibling or unrelated donor) or stem cell source (bone marrow, cord blood, or peripheral blood) With the notable exception of a study from Salamanca, 24 few data, limited to small number of patients have addressed the question of the impact of cell dose in RIC transplants. Moreover, due to the possibility to modify the stem cell content, studies addressing this question are of fundamental importance. We have tested the hypothesis that nucleated or CD34 cell dose could be associated with outcomes of patients receiving an RIC transplant. Therefore, using the European Blood and Marrow database, we have selected 253 patients with AML who received an HLA identical sibling peripheral blood stem-cell transplantation using a reduced conditioning regimen in European centers from January 1998 to April PATIENTS AND METHODS Patients The study concerned all the adult patients (n 253) that received a RIC transplant for AML with non T-cell depleted peripheral-blood cells from an HLA identical sibling, during the period of January 1, 1998, to May 1, 2004, and were reported to European Group for Blood and Marrow Transplantation (EBMT). An RIC was defined as preparative regimen with total body radiation (TBI) lower than 4 Gy and/or busulfan lower than 8 mg/kg (total dose) associated with or without fludarabine. The characteristics of the patient population, the disease, and the transplants are given in Table 1. The median age of the population was 54.5 years (range, 18 to 72). The distribution of the disease by French-American-British categories and by cytogenetics was as expected in the general population of AML patients. The nonmyeloablative pretransplant regimen included TBI at 2 Gy in 23% of the patients. Seventy-seven percent of patients received chemotherapy combinations, of which 91% included fludarabine. For GVHD prevention, 28% of patients received cyclosporine alone, 25% received cyclosporine plus mycophenolate mofetil, and 45% received cyclosporine plus methotrexate. Interestingly the majority of patients (56%) was transplanted in CR1 (n 141). The follow-up for survivors was 17 months (range, 2 to 67). End Points Acute and chronic GVHD were diagnosed and graded according to published criteria. 25,26 All patients were considered assessable for acute GVHD at day 1 after transplant. Occurrence of chronic GVHD was evaluated among patients who survived with sustained engraftment from day 100 after transplant. TRM was calculated from transplantation to death related to transplant and not to relapse. Relapse was defined on the basis of morphological evidence of leukemia in bone marrow or other extra-medullary organs. Survival was calculated from transplantation to death from any cause and leukemia-free survival (LFS) was defined as time interval from transplantation to first event, either relapse or death in CR. Table 1. Characteristics of Patients, Disease, and Transplants Nonmyeloablative Transplant Characteristic No. % WBC at diagnosis, 10 9 /L Median 9.6 Range FAB M M Cytogenetics Good 13 Intermediate 72 Poor 15 NA or failed 35 Patient age, years Median 54.5 Range Patient sex Male/female 141/112 Donor age, years Median 53 Range Donor sex Male/female 140/107 Female donor to male recipient/other 58/189 CMV Neg/neg Pos/pos Nucleated cells infused, 10 8 /kg Median 9.09 Range CD34 cells infused, 10 6 /kg Median 5.83 Range Year of transplant Median 2002 Range Status at transplant CR1 141 CR2 47 Advanced 65 GVHD Prophylaxis CSA alone CSA MMF CSA metho Abbreviations: FAB, French-American-British; NA, not available; CMV, cytomegalovirus; Neg, negative; Pos, positive; CR1, first remission; CR2, second remission; GVHD, graft-versus-host disease; CSA, cyclosporin A; MMF, mycophenolate mofetyl; metho, methotrexate. 2 M3, 10 unknown. Statistical Analysis Variables considered were recipient age and sex; disease characteristics (French-American-British classification, cytogenetics, WBC at time of diagnosis, cytomegalovirus [CMV] serology), donor characteristics (age, sex, CMV serology), disease status at transplant (CR1, second remission [CR2], or more advanced disease); transplant characteristics (conditioning regimen including TBI or not, GVHD prophylaxis, and dose of peripheral-blood cells in nucleated cells and CD34 cells:kg infused). For these prognostic analyses, continuous variables, such as cell dose, were categorized as follows. Each variable was first divided into four categories at approximately the 25th, 50th, and 75th percentiles. If the relative event rates (ratio of the observed number of events to 3960 JOURNAL OF CLINICAL ONCOLOGY

3 Reduced Conditioning Transplantations for AML the expected number of events in a category, assuming no variation across categories) in two or more adjacent categories (and the mean time-to-event) were not substantially different, these categories were grouped. 27 If a linear trend was observed in the relative event rates, the variable was used as a continuous factor. Otherwise, if no clear pattern was observed, the median was used as a cut off point. Potential prognostic factors with a P value less than.20 in univariate analyses and factors known to influence outcomes (such as status at transplant) were included in the final models. In order to test for a center effect on LFS, we introduced a random effect or frailty for each center into the model. 28,29 Cumulative incidence curves were used in a competing risks setting, death being treated as a competing event to calculate probabilities of chronic GVHD, TRM, and relapse. 30 Probabilities of survival and LFS were calculated using the Kaplan-Meier estimate; the log-rank test was used for univariate comparisons. Associations of graft characteristics with outcomes were evaluated in multivariate analyses, using Cox proportional hazards for LFS and survival, and proportional subdistribution hazard regression model of Fine and Gray for other outcomes. 31 All P values are two sided with type I error rate fixed at.05. Statistical analyses were performed with SPSS (version 11.5, SPSS Inc, Chicago, IL) and Splus (version 6.1, MathSoft Inc, Seattle, WA) software packages. RESULTS Overall Outcomes In the total population of patients at 2 years, the LFS was 41% 4%, the relapse incidence (RI) was 45% 3%, and the TRM was 13% 2%. The incidence of acute GVHD with a score of 2 or greater was 20% 2% and the incidence of chronic GVHD in patients living beyond day 100 was 50% 3%. In patients transplanted in CR1 (Figs 1 and 2), the results were 49% 6% for LFS, 37% 4% for RI, and 14% 3% for TRM. In patients transplanted in CR2, the results were 50% 8% for LFS, 34% 7% for RI, and 16% 5% for TRM. Patients who received a transplant at later stages had a poorer outcome with an LFS of 23% 6% (P 10 4 ), an RI of 69% 6% (P 10 4 ), and a TRM of 11% 3%. The incidence of acute GVHD was 19% 3% for CR1 patients, 32% 7% in CR2, and 13% 4% for more advanced diseases. The incidence of chronic GVHD was 52% 4%, 59% 9%, and 33% 8%, respectively. Fig 1. Leukemia-free survival in patients receiving a nonmyeloablative transplant for acute myelocytic leukemia, in first remission (CR1), second remission (CR2), and for more advanced disease. Fig 2. Relapse incidence and transplant-related mortality (TRM; competitive risks) in patients receiving a nonmyeloablative transplant for acute myelocytic leukemia, in first remission (CR1), second remission (CR2), and for more advanced disease. Univariate Analyses for Outcomes Table 2 gives the detailed results of the univariate analyses. In addition to the status of the disease, the use of low-dose (2 Gy) TBI in the pretransplant regimen and the dose of nucleated cells infused with the graft were potentially significant factors associated with RI and LFS, respectively. In particular, regarding the doses, higher doses resulted in better LFS (46% 5% v 37% 5%; P.03), and also a higher incidence of chronic GVHD (59% 5% v 41% 5%; P.006) with a trend for a lower incidence of relapses (42% 5% v 47% 4%; P.09). This in fact resulted from an effect in patients who received transplants in CR2 or beyond (LFS, 47% 8% v 20% 8%; P.003; chronic GVHD, 62% 9% v 31% 8%; P.006; RI, 44% 8% v 65% 7%; P.01) with no statistically significant effect in CR1. Also, the incidence of chronic GVHD was higher with donors CMV positive by serology (51% 4% v 35% 6%; P.05). We did not find any statistically significant impact of cytogenetics on outcome. Moreover, cytogenetics were evenly distributed in the groups of patients receiving doses in nucleated cells/kg below and above the median. Table 3 shows that other prognostic factors also were equally distributed between the two cell dose groups. Multivariate Analyses for Outcomes Table 4 presents the results of the multivariate analyses. There was no significant risk factor selected in the statistical model which was associated with TRM. LFS Two factors were associated with better LFS: the status of the patient at transplant (CR v more advanced) and the nucleated cell dose infused. Patients receiving doses of cells above the median had a better LFS compared with those receiving lower doses (P.036; risk ratio [RR], 0.68; 95% CI, 0.48 to 0.98; Fig 3). RI Status of the disease at transplant (CR v more advanced) and the pretransplant regimen (TBI v chemotherapy) were significant risk factors associated with increased RI. Patients receiving TBI at 2 Gy had a higher RI than patients receiving pretransplant regimens containing chemotherapy only (Fig 4; P.02; RR, 1.81; 95% CI, 1.11 to 2.93). The nucleated cell dose infused was borderline significant (P.06;

4 Gorin et al Table 2. Univariate Analyses of Prognostic Factors in Patients Receiving a Nonmyeloablative Transplant for Acute Myelocytic Leukemia in Europe (N 253) LFS RI TRM Acute GVHD Chronic GVHD Global Recipient age median median P Donor age median median P Nucleated cells (all patients, n 253) median median P Nucleated cells (CR1 patients, n 141) median median P Nucleated cells ( CR2 patients, n 112) median median P CD34 median median P Patient sex Male Female P Donor sex Male Female P Female to male No Yes P FAB M Other P TBI No Yes P Status at Tx CR CR Other P Cytogenetics Good (n 28) Intermediate (n 158) Poor (n 31) P.29 Poor v other Other (continued on next page) 3962 JOURNAL OF CLINICAL ONCOLOGY

5 Reduced Conditioning Transplantations for AML Table 2. Univariate Analyses of Prognostic Factors in Patients Receiving a Nonmyeloablative Transplant for Acute Myelocytic Leukemia in Europe (N 253) (continued) LFS RI TRM Acute GVHD Chronic GVHD CMV patient Neg Pos P CMV donor Neg Pos P CMV donor/patient Neg to neg Neg to pos Pos to neg Pos to pos P GVHD prevention CSA alone CSA MMF CSA MTX P Abbreviations: LFS, leukemia-free survival; RI, relapse incidence; TRM, transplantation-related mortality; GVHD, graft-versus-host disease; CR1, first remission; CR2, second remission; FAB, French-American-British; TBI, total body radiation; Tx, treatment; CMV, cytomegalovirus; Neg, negative; Pos, positive; CSA, cyclosporin A; MMF, mycophenolate mofetyl; metho, methotrexate. Grade 2 or higher; 100 days. Patients alive at 100 days. RR, 0.73; 95% CI, 0.47 to 1.13) with a trend for a lower RI in those receiving the higher cell dose. Chronic GVHD A higher nucleated cell dose was associated with an increase in the incidence of chronic GVHD. DISCUSSION This retrospective study concerns a series of 253 patients reported to the EBMT registry and who received transplants for AML with an HLA identical sibling, after a reduced-intensity conditioning regimen. Table 3. Distribution of Prognostic Factors in Patients Receiving Lower and Higher Doses of Nucleated Cells /Kg Dose of Cells /Kg Factor No. % No. % P CR CR2 or beyond Cytogenetics.57 Good Intermediate Poor TBI.25 No Yes Female to male.35 No Yes CMV donor serology.22 Negative Positive Abbreviations: CR1, first remission; TBI, today body irradiation; CMV, cytomegalovirus. Table 4. Multivariate Analyses of Prognostic Factors in Patients Receiving a Nonmyeloablative Transplant for Acute Myelocytic Leukemia in Europe (N 253) Factor RR 95% CI P LFS Nucleated cells median to Female to male v other.1 CR v other to Team (frailty).34 RI Nucleated cells median to TBI to CR v other to Team.83 Acute GVHD (grade 2) NS Chronic GVHD Nucleated cells median to CMV donor positive.44 CR v other.8 Team.59 Abbreviations: RR, risk ratio; LFS, leukemia-free survival; CR, complete remission; RI, relapse incidence; TBI, total body radiation; GVHD, graft-versushost disease, NS, not significant; CMV, cytomegalovirus

6 Gorin et al Fig 3. Impact of the nucleated cell dose infused: leukemia-free survival of patients receiving doses above and below the median value. Since RIC is still an emergent new transplant modality, this series appears at the time of this publication to be the largest available and it conveys several important pieces of information on demographics, outcome of patients, and prognostic factors among which the nature of the reduced-intensity pretransplant regimen and the cell dose infused appear important. While RIC has been originally applied to older patients and/or patients at higher risk of toxicity and TRM, usually translating into patients with more advanced disease, it is of interest in this European series that despite an expected elevated median age of 54.5 years, the range was very wide and included patients as young as 18 years of age (52 patients were younger than 45 years of age). In addition, more than 50% of the patient population received a transplant in CR1. One might conclude from this first observation that RIC has gained recognition in the treatment of AML and is being used more widely, with indications reaching younger patients and earlier stages of the disease than originally designed for. In this survey, patients who received transplants in CR1 and CR2 (Figs 1 and 2) had a similar LFS at 2 years of approximately 50%, a similar RI at approximately 35%, and a similar TRM at approximately 15%. These results suggest that RIC transplant can possibly be delayed Fig 4. Impact of the pretransplantation regimen: relapse incidence (RI) and transplantation-related mortality (TRM; competitive risks) in patients receiving a nonmyeloablative transplant for acute myelocytic leukemia with a conditioning regimen with or without total body radiation (TBI) at the dose of 2 Gy. to CR2, although this statistical finding is not necessarily easy to apply to individual patients at time of initial diagnosis or while in CR1 because in case of relapse, reaching a CR2 cannot be guaranteed. In contrast, patients who received transplants at later stages had a much worse outcome with a very high RI at approximately 70% leading to a poor LFS of only 23%. This information is valuable because, despite a considerable number of reports already published on RIC, there has been little indication on the benefit in patients with AML. With the exception of the recent multicenter retrospective study with a total of 122 patients with AML, which compared the outcome of transplants with related and unrelated donors, 32 most retrospective reports have concerned small series of patients from single institutions 33 and larger series, still limited, have combined various diseases. 34,35 Using a genetic random assignment through a donor versus no donor comparison among 95 adult high-risk acute myeloid leukemia patients, Mohty et al 36 found in an intention-to-treat analysis, that LFS and overall survival were significantly higher in the donor group who received a RIC transplant with a genoidentical donor as compared with the no donor group who received chemotherapy only. However, the key question at the present is the comparison of RIC to conventional transplants. There have been no randomized studies addressing this question, although some are being planned. A retrospective comparison has recently been done by the Acute Leukemia Working Party of the EBMT in patients older than 50 years of age. 37 In this study, patients receiving an RIC had, at 2 years, a disease-free survival of 40% 3% and an overall survival of 47% 3%, which was not different from the figures found after a conventional transplant. This study, of course, was not designed to compare genoidentical allogeneic stem-cell transplants to other transplant modalities. Its goal was in fact to identify prognostic factors of RIC transplants in AML. Obviously, in addition to the short follow-up, the series presented here suffers from the usual limitation of retrospective registry studies; however, it gives a rough estimate of a possible outcome in a very heterogeneous population of patients with AML, which regroups all patients with AML receiving a nonmyeloablative stem cell transplantation since the initiation of this new transplant modality. This patient population contains a large fraction of patients who have been selected for RIC and not conventional transplant because of their age, and indeed this has been confirmed as following transplant policies of the centers in a previous EBMT survey. However, we have no indication why so many younger patients have received RIC in CR1 rather than conventional transplants and we only can assume that the medical teams had in many, if not all of them, identified adverse conditions with a higher risk of TRM. RIC transplant is not a standardized modality. Patients receiving RIC are conditioned with various pretransplant regimen, some containing TBI at 2 Gy as originally designed by the Seattle team, 10 other containing chemotherapy only, which most frequently contained fludarabin as initially proposed by Slavin et al. 38 The graft itself is not standardized for the dose of cells infused. When planning the analysis of prognostic factors, we were particularly interested in these two variables. Our finding that TBI alone at 2 Gy was associated with a higher RI is in agreement with the known reduced antileukemic effect of this low-dose radiation and the efficacy of fludarabin and other chemotherapeutic agents usually combined to it, such as cyclophosphamide, busulfan, or melphalan. The dose of cells infused for a transplant has long been recognized as an important parameter for outcome and a considerable number of studies in patients receiving a 3964 JOURNAL OF CLINICAL ONCOLOGY

7 Reduced Conditioning Transplantations for AML conventional allogeneic transplant have clearly shown that higher stem cell doses infused improve the outcome through a decrease of the TRM, and also in some studies and somewhat less expected, a reduction of RI This RI reduction has been attributed to a graft-versusleukemia effect mediated by higher doses of T cells in richer grafts and/or a competition effect whereby the normal hematopooietic stem cell compartment somehow refrains the leukemic clone development by other means. 19,23 While the same scheme could apply to RIC, we were concerned that the situation might differ in that RIC transplant is a specific model of GVHD/graft-versus-leukemia induction with minimal antitumor effect provided by the conditioning, where there could be an optimal stem cell dose window to infuse to get a maximum graft-versus-leukemia effect with a minimum TRM resulting from GVHD. 39 Recent studies in RIC transplants have shown the impact of the stem-cell graft composition on the outcome; in particular, higher numbers of CD34 cells resulted in more rapid T-cell engraftment, higher incidence of chronic GVHD, and better survivals. 40,41 This study in fact shows an interaction between the cell dose and the status of the disease at transplant: higher nucleated cell doses benefited patients transplanted in CR2 or more advanced disease, with higher LFS and lower RI. There was no detectable benefit in CR1. All prognostic factors including cytogenetics were evenly distributed. In a recent study from Salamanca 24 on a smaller population of 86 patients receiving RIC for various malignancies, higher cell doses (above the 75th percentile) were infused, evaluated in CD34 /kg, and were associated with lower RI, but in high-risk patients only. Although we found an effect with the nucleated cell dose, but not with the CD34 cell dose (Fig 5), our study shares some similarity with the report from Salamanca, and likewise suggests that infusing high-cell doses may ameliorate the negative effect of advanced disease status. Unfortunately, the registry did not contain exhaustive information and while we had information on the nucleated cell dose and the CD34 cell Fig 5. Leukemia-free survival according to the CD34 cell dose infused. dose infused, we were unable to get information on the doses of T cells. The finding that the nucleated cell dose but not the CD34 cell dose impacted the outcome may suggest a role for the dose of T-cells infused with the graft. In this study, as in a previous EBMT studies on the impact of cell doses after conventional genoidentical allogeneic transplants for AML, we found no correlation with the incidence and severity of acute GVHD, but as already shown with peripheral blood CD 34 doses and not with marrow a correlation with the incidence of chronic GVHD which supports the accompanying T and dendritic cell dose increase impact. 42 In fact, a CD8 dose range window for a better outcome has been reported as existing in the context of RIC, including the administration of antithymocyte globulin by the Marseille team, albeit on a much smaller patient population combining various hematological malignancies. 43 Therefore, it is important to take this into account when infusing the graft. REFERENCES 1. Appelbaum FR, Clift RA, Buckner CD, et al: Allogeneic marrow transplantation for acute nonlymphoblastic leukemia after first relapse. Blood 61: , Santos GW, Tutschka PJ, Brookmeyer R, et al: Marrow transplantation for acute nonlymphocytic leukemia after treatment with busulfan and cyclophosphamide. N Engl J Med 309: , 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 49: , Thomas ED, Buckner CD, Clift RA, et al: Marrow transplantation for acute nonlymphoblastic leukemia in first remission. N Engl J Med 301: , Frassoni F, Labopin M, Gluckman E, et al: Results of allogeneic bone marrow transplantation for acute leukemia have improved in Europe with time A report of the acute leukemia working party of the European group for blood and marrow transplantation (EBMT). Bone Marrow Transplant 17:13-18, Ringden O, Horowitz MM, Gale RP, et al: Outcome after allogeneic bone marrow transplant for leukemia in older adults. JAMA 270:57-60, Bertz H, Potthoff K, Finke J: Allogeneic stemcell transplantation from related and unrelated donors in older patients with myeloid leukemia. J Clin Oncol 21: , Champlin R, Khouri I, Shimoni A, et al: Harnessing graft-versus-malignancy: Non-myeloablative preparative regimens for allogeneic haematopoietic transplantation, an evolving strategy for adoptive immunotherapy. Br J Haematol 111:18-29, Giralt S, Estey E, Albitar M, et al: Engraftment of allogeneic hematopoietic progenitor cells with purine analog-containing chemotherapy: Harnessing graft-versus-leukemia without myeloablative therapy. Blood 89: , McSweeney PA, Niederwieser D, Shizuru JA, et al: Hematopoietic cell transplantation in older patients with hematologic malignancies: Replacing high-dose cytotoxic therapy with graft-versus-tumor effects. Blood 97: , Shimoni A, Giralt S, Khouri I, et al: Allogeneic hematopoietic transplantation for acute and chronic myeloid leukemia: Non-myeloablative preparative regimens and induction of the graft-versus-leukemia effect. Curr Oncol Rep 2: , Shimoni A, Nagler A: Non-myeloablative stem cell transplantation (NST): Chimerism testing as guidance for immune-therapeutic manipulations. Leukemia 15: , Shimoni A, Nagler A: Non-myeloablative hematopoietic stem cell transplantation (NST) in the treatment of human malignancies: From animal models to clinical practice. Cancer Treat Res 110: , Slavin S, Aker M, Shapira MY, et al: Reducedintensity conditioning for the treatment of malignant and life-threatening non-malignant disorders. Clin Transpl , Slavin S: Reduced intensity versus truly nonmyeloablative conditioning for stem-cell transplant recipients. Transplantation 78: , Wong R, Giralt SA, Martin T, et al: Reducedintensity conditioning for unrelated donor hematopoietic stem cell transplantation as treatment for myeloid malignancies in patients older than 55 years. Blood 102: , Horowitz MM, Gale RP, Sondel PM, et al: Graft-versus-leukemia reactions after bone marrow transplantation. Blood 75: , Bittencourt H, Rocha V, Chevret S, et al: Association of CD34 cell dose with hematopoietic recovery, infections, and other outcomes after HLAidentical sibling bone marrow transplantation. Blood 99: , Gorin NC, Labopin M, Laporte JP, et al: Importance of marrow dose on posttransplant outcome in acute leukemia: Models derived from patients autografted with mafosfamide-purged marrow at a single institution. Exp Hemat 27: , Gorin NC, Labopin M, Rocha V, et al: Marrow versus peripheral blood for geno-identical allogeneic stem cell transplantation in acute myelocytic leukemia: Influence of dose and stem cell source shows better outcome with rich marrow. Blood 102: , Rocha V, Labopin M, Gluckman E, et al: Relevance of bone marrow cell dose on allogeneic transplantation outcomes for patients with acute myeloid

8 Gorin et al leukemia in first complete remission: Results of a European survey. J Clin Oncol 20: , Sierra J, Storer B, Hansen JA, et al: Transplantation of marrow cells from unrelated donors for treatment of high-risk acute leukemia: The effect of leukemic burden, donor HLA matching and marrow cell dose. Blood 89: , Gorin NC, Labopin M, Pichard P, et al: Feasibility and recent improvement of autologous stem cell transplantation for acute myelocytic leukaemia in patients over 60 years of age: Importance of the source of stem cells. Br J Haematol 110: , Perez-Simon JA, Diez-Campelo M, Martino R, et al: Impact of CD34 cell dose on the outcome of patients undergoing reduced-intensity-conditioning allogeneic peripheral blood stem cell transplantation. Blood 102: , Glucksberg H, Storb R, Fefer A, et al: Clinical manifestations of graft-versus-host disease in human recipients of marrow from HLA-matched sibling donors. Transplantation 18: , Rowlings PA, Przepiorka D, Klein JP, et al: IBMTR severity index for grading acute graft-versushost disease: Retrospective comparison with Glucksberg grade. Br J Haematol 97: , Byar DP: Identification of prognostic factors, in Buyse ME, Staquet MJ, Sylvester RJ (eds): Cancer Clinical Trials Methods and Practice. Oxford, United Kingdom, Oxford Medical Publications, 1988, pp Andersen PK, Klein JP, Zhang MJ: Testing for centre effects in multi-centre survival studies: A Monte Carlo comparison of fixed and random effects tests. Stat Med 18: , Hoogard P: Frailty model for survival data. Lifetime Data Anal 1: , Gooley TA, Leisenring W, Crowley J, et al: Estimation of failure probabilities in the presence of competing risks: New representations of old estimators. Stat Med 18: , Fine JP, Gray RJ: A proportional hazards model for subdistribution of a competing risk. Journal of American Statistical Association 94: , Hegenbart U, Niederwieser D, Sandmaier BM, et al: Treatment for acute myelogenous leukemia by low-dose, total-body, irradiation-based conditioning and hematopoietic cell transplantation from related and unrelated donors. J Clin Oncol 24: , Blaise DP, Michel Boiron J, Faucher C, et al: Reduced intensity conditioning prior to allogeneic stem cell transplantation for patients with acute myeloblastic leukemia as a first-line treatment. Cancer 104: , Alyea EP, Kim HT, Ho V, et al: Comparative outcome of nonmyeloablative and myeloablative allogeneic hematopoietic cell transplantation for patients older than 50 years of age. Blood 105: , Shimoni A, Kroger N, Zabelina T, et al: Hematopoietic stem-cell transplantation from unrelated donors in elderly patients (age 55 years) with hematologic malignancies: Older age is no longer a contraindication when using reduced intensity conditioning. Leukemia 19:7-12, Mohty M, de Lavallade H, Ladaique P, et al: The role of reduced intensity conditioning allogeneic stem cell transplantation in patients with acute myeloid leukemia: A donor vs no donor comparison. Leukemia 19: , Aoudjhane M, Labopin M, Gorin NC, et al: Comparative outcome of reduced intensity and myeloablative conditioning regimen in HLA identical sibling allogeneic haematopoietic stem cell transplantation for patients older than 50 years of age with acute myeloblastic leukaemia: A retrospective survey from the Acute Leukemia Working Party (ALWP) of the European group for Blood and Marrow Transplantation (EBMT). Leukemia 19: , Slavin S, Nagler A, Naparstek E, 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 91: , Ringden O, Hermans J, Labopin M, et al: The highest leukaemia-free survival after allogeneic bone marrow transplantation is seen in patients with grade I acute graft-versus-host disease: Acute and Chronic Leukaemia Working Parties of the European Group for Blood and Marrow Transplantation (EBMT). Leuk Lymphoma 24:71-79, Baron F, Maris MB, Storer BE, et al: High doses of transplanted CD34 cells are associated with rapid T-cell engraftment and lessened risk of graft rejection, but not more graft-versus-host disease after nonmyeloablative conditioning and unrelated hematopoietic cell transplantation. Leukemia 19: , Panse JP, Heimfeld S, Guthrie KA, et al: Allogeneic peripheral blood stem cell graft composition affects early T-cell chimaerism and later clinical outcomes after non-myeloablative conditioning. Br J Haematol 128: , Mielcarek M, Martin PJ, Heimfeld S, et al: CD34 cell dose and chronic graft-versus-host disease after human leukocyte antigen-matched sibling: Hematopoietic stem cell transplantation: Leukemia Lymphoma 45:27-34, Mohty M, Bagattini S, Chabannon C, et al: CD8 T cell dose affects development of acute graft versus host disease following reduced-intensity conditioning allogeneic peripheral blood stem cell transplantation. Exp Hematol 32: , 2004 Appendix The Appendix is included in the full-text version of this article, available online at It is not included in the PDF version (via Adobe Reader ). Authors Disclosures of Potential Conflicts of Interest The authors indicated no potential conflicts of interest. Author Contributions Conception and design: Norbert-Claude Gorin, Myriam Labopin, Vanderson Rocha Financial support: Vanderson Rocha Administrative support: Norbert-Claude Gorin, Myriam Labopin, Vanderson Rocha Provision of study materials or patients: Jean-Michel Boiron, Niklas Theorin, Tim Littlewood, Shimon Slavin, Hildegard Greinix, Jean Yves Cahn, E. Paolo Alessandrino, Alessandro Rambaldi, Arnon Nagler, Vanderson Rocha Collection and assembly of data: Myriam Labopin, Emmanuelle Polge Data analysis and interpretation: Myriam Labopin, Vanderson Rocha Manuscript writing: Norbert-Claude Gorin Final approval of manuscript: Norbert-Claude Gorin, Myriam Labopin, Jean-Michel Boiron, Niklas Theorin, Tim Littlewood, Shimon Slavin, Hildegard Greinix, Jean Yves Cahn, E. Paolo Alessandrino, Alessandro Rambaldi, Arnon Nagler, Vanderson Rocha 3966 JOURNAL OF CLINICAL ONCOLOGY