Allogeneic Hematopoietic Cell Transplantation for Chronic Myelomonocytic Leukemia

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1 Biology of Blood and Marrow Transplantation 11: (2005) 2005 American Society for Blood and Marrow Transplantation /05/ $30.00/0 doi: /j.bbmt Allogeneic Hematopoietic Cell Transplantation for Chronic Myelomonocytic Leukemia Daniella M. B. Kerbauy, 1 Faith Chyou, 1 Ted Gooley, 1,2 Mohamed L. Sorror, 1,2 Bart Scott, 1,2 John M. Pagel, 1 David Myerson, 1,2 Frederick R. Appelbaum, 1,2 Rainer Storb, 1,2 H. Joachim Deeg 1,2 1 Fred Hutchinson Cancer Research Center, Seattle, Washington; 2 University of Washington, Seattle, Washington Correspondence and reprint requests: H. Joachim Deeg, MD, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave. N., D1-100, P.O. Box 19024, Seattle, WA ( jdeeg@fhcrc.org). Received March 29, 2005; accepted May 20, 2005 ABSTRACT We evaluated the outcomes of allogeneic hematopoietic cell transplantation (HCT) in 43 patients with chronic myelomonocytic leukemia. Patients were classified according to the French-American-British and World Health Organization classifications, as well as the International Prognostic Scoring System and the M.D. Anderson prognostic score. Comorbidity scores were assessed by using an HCT-specific comorbidity index. Patients were aged 1 to 66 years (median, 48 years). Twenty-one patients received transplants from related donors (18 HLA-identical siblings and 3 HLA-nonidentical family members), and 22 received transplants from unrelated donors (18 HLA matched and 4 HLA nonidentical). Several busulfan or total body irradiation based conditioning regimens were used. Sustained engraftment was achieved in 41 patients. Eighteen are alive at 1.9 to 14.1 years, for an estimated relapse-free survival of 41% at 4 years. Ten patients have relapsed, thus leading to a cumulative incidence of 23% at 4 years. Risk category by International Prognostic Scoring System, World Health Organization, M.D. Anderson prognostic score, or proliferative/dysplastic status had no statistically significant association with outcomes. However, patients with higher comorbidity scores had worse overall survival than patients with lower scores (P.01). There was a trend for a higher relapse incidence among patients at higher risk by the M.D. Anderson prognostic score. The data suggest that patients with few or no comorbidities and those who undergo transplantation earlier in the disease course have the highest probability of successful outcome after allogeneic HCT American Society for Blood and Marrow Transplantation KEY WORDS Chronic myelomonocytic leukemia Allogeneic transplantation Relapse-free survival Comorbid conditions INTRODUCTION Chronic myelomonocytic leukemia (CMML) is a myeloid disorder, often with features of myelodysplasia and, more prominently, myeloproliferation, classified by the World Health Organization (WHO) as a myelodysplastic/myeloproliferative disorder [1]. To date, no specific cytogenetic or molecular distinction is possible between patients with more dysplastic and those with more proliferative features. According to the WHO, the disorder is subdivided into CMML-1 and CMML-2 according to the proportion of myeloblasts in peripheral blood and marrow and the presence or absence of Auer rods [1]. Investigators at M.D. Anderson have proposed a new prognostic classification that is based on analysis of disease characteristics BB&MT and survival in 213 patients with CMML [2]. Although the median survival was 12 months, they identified 4 subgroups of patients with median survivals of 24, 15, 8, and 5 months on the basis of hemoglobin levels, the presence of circulating immature myeloid cells, the absolute lymphocyte count, and the marrow myeloblast proportion. Despite the designation as a chronic leukemia, CMML is a progressive disease that often leads to death within months. Various chemotherapy regimens have been used, including hydroxyurea, etoposide, low-dose cytosine arabinoside, or more intensive combinations of cytotoxic agents such as anthracycline and cytosine arabinoside. However, responses to such therapies have generally been short. More recently developed agents, such as farne- 713

2 D. M. B. Kerbauy et al. syl transferase inhibitors, have met with limited success [3,4]. The tyrosine kinase inhibitor imatinib mesylate (STI571) may induce remissions, but typically only in patients with mutations or gene rearrangements (for example, involving platelet-derived growth factor receptor ) that generate appropriate targets [5]. The only currently available therapy that offers the potential for cure is hematopoietic cell transplantation (HCT) [6-8]. We previously reported results with allogeneic transplantation in 21 patients with CMML [6]. Here, we update our data and summarize results in 43 patients treated at the Fred Hutchinson Cancer Research Center (FHCRC) in Seattle, WA. PATIENTS AND METHODS Patients Between June 1990 and January 2004, 43 patients with CMML received transplants from allogeneic donors at the FHCRC. Patient and disease characteristics are summarized in Table 1. The diagnosis of CMML was initially based on the French-American- British classification. For the purpose of this analysis, the disease was also classified according to WHO criteria [1]. In addition, we categorized patients for whom all required parameters were available according to the 4 risk groups recently proposed by Onida et al. [2] (M.D. Anderson Prognostic Score [MDAPS]). All classifications in this analysis were based on findings at the time of transplantation rather than at diagnosis. Patients were 1 to 66 years (median, 48 years) of age at the time of transplantation. Twenty-five patients were male, and 18 were female. The interval from diagnosis to transplantation was 2 to 156 months (median, 8 months). At the time of transplantation, 16 patients were classified as having proliferative CMML (white blood cell count [WBC] of /L), and 27 had nonproliferative CMML (WBC of /L) [9]. Lymphocyte counts ranged from 0.04 to /L, with a median of /L. Five patients had what was considered secondary CMML after therapy for aplastic anemia (n 2), Hodgkin disease (n 1), POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, M protein, and skin changes; n 1), and chronic lymphocytic leukemia (n 1). Three patients had undergone splenectomy. Twelve patients had received either no treatment or transfusion only before transplantation. Fourteen patients had received hydroxyurea, 6 had received steroids or erythropoietin (or both), 2 had received imatinib, and 9 had received various kinds of chemotherapy other than hydroxyurea. There were 26 patients with nonproliferative CMML who could be scored according to the International Prognostic Scoring System (IPSS). Table 1. Patient Characteristics at Transplantation Variable Data Population studied 43 Age (y) 48 (1-66) Sex (male/female) 25/18 Disease duration (mo) 8 (2-156) Diagnosis Proliferative 16 Nonproliferative 27 WHO CMML-1/2 32/11 IPSS risk (26 scored) Low 4 Int-1 11 Int-2 8 High 3 MDAPS Low 18 Int-1 9 Int-2 12 High 4 CMV serology ( / ) 24/19 Hematologic parameters Lymphocytes ( 10 9 /L) 1.8 ( ) WBC/ANC ( 10 9 /L) 8.8 ( )/2.913 ( ) Platelets ( 10 9 /L) 59 (3-594) Hemoglobin (g/dl) 10.2 ( ) Cytogenetic findings Normal 23 Monosomy 7 ( others) 5 Other abnormalities 15 Pretransplantation therapy None 9 Transfusion only 3 Imatinib 2 Hydroxyurea 14 Combination chemotherapy 9 Erythropoietin 2 Prednisolone 4 Splenectomy 3 WHO indicates World Health Organization; IPSS, International Prognostic Scoring System; MDAPS, M.D. Anderson Prognostic Score; CMV, cytomegalovirus; Int, intermediate; ANC, absolute neutrophil count. Data are n or median (range). Among these, 4 were low risk, 11 were intermediate 1, 8 were intermediate 2, and were 3 high risk [10]. By IPSS criteria, 23 patients had good-risk cytogenetics (normal karyotype), 9 had poor-risk cytogenetics (monosomy 7 in 5 and complex abnormalities in 4 patients), and 11 had intermediate-risk cytogenetics (3 with trisomy 8, single miscellaneous in 5, and double miscellaneous in 2). Overall, 32 patients had CMML-1 and 11 had CMML-2 by WHO criteria. By the M.D. Anderson criteria, considering hemoglobin 12 g/dl, immature myeloid cells in peripheral blood, marrow blasts 10%, and absolute lymphocyte counts of /L,18patients were in the low-risk category, 9 were intermediate 1, 12 were intermediate 2, and 4 were in the high-risk category. 714

3 Allogeneic Transplants for CMML Comorbidities Information concerning comorbidities was obtained through medical chart review. Comorbidities were scored by using a recently developed HCTspecific comorbidity index (HCT-SCI). This index was developed by modifying the Charlson comorbidity index [11], and it has shown good prediction for the risks of nonrelapse mortality and overall survival [12]. Specific comorbidities, definitions, and assigned weights were assessed as previously described [13]. HCT-SCI could be applied for 42 patients. Thirteen patients had a score of 0; 5, a score of 1; 11, a score of 2; 8, a score of 3; 2, a score of 4; 1, a score of 5, and 2, a score of 6 [12]. Donors and Sources of Hematopoietic Stem Cells Transplant characteristics are summarized in Table 2. Patients and donors were typed for HLA-A, -B, -C, -DRB1, and -DQB1. Eighteen patients received marrow from HLA-identical siblings, 3 from HLAnonidentical family members (parent, sibling, or child differing for HLA-A; HLA-A, -B, and -DR; and HLA-A and -DR, respectively), 17 from HLAmatched unrelated donors, and 5 from HLA-nonidentical unrelated donors. Among these, 3 differed from the patients for HLA-A, and 2 differed from the patients for HLA-DR. All HLA-nonidentical transplants were from donors mismatched at the antigen level. Twenty-three patients received bone marrow, and 20 patients received granulocyte colony-stimulating factor mobilized peripheral blood as the source of stem cells. Conditioning Regimen The conditioning regimens used were determined by sequential protocols designed for patients with myelodysplastic syndrome (MDS) that were active at the time of transplantation (Table 2). Nine patients were conditioned with busulfan (BU) 7 mg/kg orally, cyclophosphamide (CY) 50 mg/kg intravenously, and total body irradiation (TBI) cgy over 3 days for a total of 12 Gy. Eight patients received BU 7 mg/kg orally and fractionated TBI cgy over 3 days for a total of 12 Gy. Four patients received fludarabine 120 mg/m 2 intravenously over 3 days and BU 16 mg/kg orally over 4 days (targeted to plasma levels of ng/ml). Three patients received targeted BU 16 mg/kg, CY 120 mg/kg, and antithymocyte globulin (Thymoglobulin; Genzyme, Cambridge, MA) 4.5 mg/kg over 3 days. Three patients received CY 120 mg/kg and TBI 14.4/13.2 Gy, and 12 patients received BU 16 mg/kg and CY 120 mg/kg. Of the remaining 4 patients, 1 received BU 7 mg/kg, TBI 12 Gy, and amifostine 340 mg/m 2 ; 1 received CY 120 mg/kg, antithymocyte globulin 90 mg/kg, and TBI 13.2 Gy; 1 received fludarabine 90 mg/m 2 and TBI 2.0 BB&MT Table 2. Donor and Transplant Characteristics Variable Data Donor age, y, median (range) 38 (3-69) Sex (male/female) 26/17 Donor/patient CMV status / 13 / 6 / 16 / 8 Donor-patient relationship HLA-identical sibling 18 HLA-nonidentical related donor 3 HLA-identical unrelated donor 17 HLA-nonidentical unrelated donor 5 Preparative regimen BU (7 mg/kg)/cy (50 mg/kg)/tbi (12 Gy) 9 BU (7 mg/kg)/tbi (12 Gy) 8 BU (7 mg/kg)/tbi (12 Gy)/amifostine (340 mg/m 2 ) 1 BU (14 mg/kg)/cy (120 mg/kg) 12 BU (16 mg/kg)/cy (120 mg/kg)/thy (4.5 mg/kg) 3 CY (120 mg/kg)/tbi (14.4/13.2 Gy) 3 CY (120 mg/kg)/atg (90 mg/kg)/tbi (13.2 Gy) 1 FLU (90 mg/m 2 )/TBI (2 Gy) 1 FLU (120 mg/m 2 )/BU (16 mg/kg) 4 TBI (2.0 Gy)/iodine 131 anti-cd45 antibody 1 GVHD prophylaxis CSP/MTX 38 CSP/MTX/prednisone 2 CSP/prednisone 2 MTX/tacrolimus 1 Cells transplanted, median (range) Bone marrow cell dose: ( ) 10 8 /kg 23 Peripheral blood stem cells, CD34 cell dose: ( ) 10 6 /kg 20 CMV indicates cytomegalovirus; BU, busulfan; CY, cyclophosphamide; TBI, total body irradiation; FLU, fludarabine; ATG, antithymocyte globulin (Thymoglobulin); CSP, cyclosporine; MTX, methotrexate. Data are numbers of patients unless otherwise noted. Gy; and 1 received TBI 2.0 Gy plus iodine 131 anti- CD45 antibody (approximately 18 Gy was delivered to liver plus bone marrow) [14-20]. Graft-versus-Host Disease Prophylaxis Graft-versus-host disease (GVHD) prophylaxis consisted of cyclosporine and methotrexate in 38 patients. Two patients were treated with prednisone in addition to the cyclosporine and methotrexate, 2 were treated with cyclosporine and prednisone, and 1 was treated with methotrexate and tacrolimus [21-23]. Evaluation Time of engraftment was defined as the first of 3 consecutive days on which the absolute neutrophil count reached /L [24]. GVHD was determined by previously established criteria [21,25]. Survival time was the time from transplantation until death or the date of last contact. Relapse-free survival was the time from transplantation until relapse or death from non relapse-related causes. Relapse was 715

4 D. M. B. Kerbauy et al. defined as the detection of reappearance of morphologic criteria of CMML or detection of previously present cytogenetic abnormalities. Statistical Analysis Overall and relapse-free survivals were summarized by using the Kaplan-Meier method [26], and relapse probabilities were obtained from cumulative incidence estimates. Death without relapse (nonrelapse mortality) was considered a competing risk for relapse. Cox regression was used to assess the association of various factors with each of these outcomes. Factors analyzed included IPSS, WHO, MDAPS, and HCT-SCI scoring systems; age; duration of disease; presence of proliferative disease; and the use of highdose TBI as part of the conditioning. The association of GVHD with outcome was assessed by modeling GVHD as a time-dependent covariate. All 2-sided P values associated with regression models were obtained by using the Wald test, and no adjustments were made for multiple comparisons. Results were analyzed as of July 1, RESULTS Engraftment Sustained engraftment was achieved in 41 of the 43 patients. Neutrophil counts of /L were reached at a median of 19 days (range, days). Two patients died without meeting hematologic criteria for engraftment, although 1 of these had clinical and histologic evidence of acute GVHD. Relapse Recurrence (or progression) of CMML occurred in 10 patients at 45 to 657 days (median, 150 days) after transplantation. The estimated probability of relapse at 4 years was 23%. There were no statistically significant correlations between the hazard of relapse and IPSS score, WHO classification, age, use of highdose TBI, or disease duration before transplantation (Table 3). Patients with proliferative disease had a slightly lower hazard of relapse, but outcome was not statistically significantly different from that in patients with nonproliferative disease. There was a suggestion that the hazard of relapse was higher with a higherrisk classification by MDAPS (hazard ratio [HR], 3.79; 95% confidence interval [CI], ; P.09). No correlation of comorbidity index with relapse was observed (Table 3). Six (33%) of 18 patients without chronic GVHD relapsed, compared with 4 (19%) of 21 with chronic GVHD. With the numbers of observations available, there was no significant correlation between GVHD and relapse. Causes of Death Causes of death are summarized in Table 4. Ten patients died with relapse of CMML. Fifteen patients (34%) died from complications related to the transplantation (nonrelapse mortality), including 8 patients with infections with or without concurrent GVHD and 5 patients with multiorgan failure. Overall and Relapse-Free Survival With a follow-up of 230 to 5135 days (median, 2096 days), 18 patients are alive in remission for an estimated overall (and relapse-free) survival at 4 years of 41% (Figure 1). All patients who relapsed died, and the time from relapse to death was less than 100 days for 6 of the 10 patients. As a result, regression models for overall and relapse-free survival are similar, and we present those for overall survival only. Six of the 18 patients who received transplants from HLA-identical siblings, 3 of 3 who received transplants from HLAnonidentical relatives, 8 of 17 who received transplants from HLA-identical unrelated donors, and 1 of 5 who received transplants from HLA-nonidentical unrelated donors are alive. Patients with grade II to IV acute GVHD had a higher hazard of mortality than did patients with grade 0 or I acute GVHD; however, the difference was not statistically significant (HR, 1.34; 95% CI, ; P.47). Survival was also comparable for patients with and without chronic GVHD (HR, 1.06; 95% CI, ; P.92). With the number of patients available, no significant effect of conditioning regimen on outcome was observed. In particular, there was no significant difference between patients conditioned with high-dose TBI and those prepared with chemotherapy-only regimens (Table 3). There were no statistically significant associations between overall survival and IPSS, WHO, or MDAPS, nor with classification as proliferative versus nonproliferative or with disease duration before transplantation. Increasing age was suggestively associated with an increased hazard of death (Table 3). Sorror et al. [13] showed in a previous study that a breakdown by scores into 0, 1 to 2, and 3 was useful to evaluate risks of nonrelapse mortality and overall survival. Here, patients were categorized into 2 groups only, by scores of 0 to 2 and 3, because of the small cohort size. Patients with comorbidity scores of 3 had an increased hazard of mortality compared with those who had lower scores (HR, 2.81; 95% CI, ; P.01). The corresponding probabilities of surviving in remission were 15% and 54% for patients with comorbidity scores 0 to 2 and 3, respectively (Figure 2). The comorbidities present in patients with scores of 3 are summarized in Table

5 Allogeneic Transplants for CMML Table 3. Hazard Rates for Relapse, Nonrelapse Mortality, and Mortality by Various Characteristics and Scoring Systems Characteristic/Score Relapse Nonrelapse Mortality Mortality IPSS ( ; P.48) 0.38 ( ; P.23) 0.74 ( ; P.55) WHO CMML CMML ( ; P.47) 0.38 ( ; P.2) 0.77 ( ; P.58) M.D. Anderson ( ; P.09) 0.98 ( ; P.98) 1.51 ( ; P.32) HCT-SCI ( ; P.92) 4.36 ( ; P.006) 2.81 ( ; P.01) Nonproliferative CMML Proliferative CMML 0.66 ( ; P.54) 1.0 ( ; P.99) 0.82 ( ; P.63) Disease duration <12 mo >12 mo 0.89 ( ; P.87) 1.86 ( ; P.23) 1.45 ( ; P.36) Age* 1.23 ( ; P.42) 1.49 ( ; P.11) 1.38 ( ; P.08) Conditioning regimen No TBI High-dose TBI 1.12 ( ; P.87) 0.79 ( ; P.66) 0.87 ( ; P.74) IPSS indicates International Prognostic Scoring System; WHO, World Health Organization; HCT-SCI, hematopoietic cell transplantation specific comorbidity index. Shown for the 3 end points are the reference value (1) and the relative hazard rate for the comparison value (with confidence interval and P value). *Age was modeled as a continuous linear variable; hazard ratio represents the increase in hazard associated with an increase in age of 10 years. Excludes the patients who received nonmyeloablative transplants. BB&MT DISCUSSION CMML is a hematopoietic stem cell disorder with heterogeneous clinical presentation. The classification remains a matter of debate. The WHO classified CMML in a new category of MDS/myeloproliferative disease [1]. Previously, the total WBC had been considered to distinguish between truly dysplastic (MDS- CMML; WBC /L) and proliferative (myeloproliferative disease-cmml; WBC /L) types [9]. However, although the distinction of proliferative and nonproliferative subtypes has provided relevant survival information in some series, the prognostic significance of this classification has been questioned [27-29]. A prognostic scoring system proposed by the M.D. Anderson team categorizes patients on the basis of clinical features into low-risk, intermediate 1 or 2, and high-risk groups with median life expectancies ranging from 5 to 24 months. This emphasizes that despite the chronic nature implied by the term, CMML is often a rapidly progressive disease and that effective therapeutic strategies are needed. HCT offers potentially curative therapy for patients with CMML; however, the risk of fatal complications is high, and the relevance of the various classification schemes to posttransplantation outcomes is not clear. Here, we present an update of results in patients with CMML who underwent transplantation at the FHCRC. We analyzed posttransplantation outcomes depending on pretransplantation classification and risk assessments. Overall, the data confirm the results reported previously in a smaller cohort of patients [6], with estimated overall and relapse-free survival at 4 years of 41%. These results compare favorably to those of Kroger et al. [7], who observed a relapse-free survival of 18% at 40 months. However, that study included patients from multiple institutions, some of whom had received T cell depleted transplants; this might have contributed to a higher relapse rate than that reported here. This observation would suggest a graft-versus-leukemia effect in patients with CMML, even though in this study the relapse incidence in patients with and without GVHD did not differ significantly. In disagreement with our previous report [6], but in agreement with reports by others [7,8], disease duration by itself had no statistically significant effect on outcome. Furthermore, indicators of prognostic significance for the natural disease course, such as WHO classification and IPSS scores, failed to convincingly define groups of patients with superior or inferior outcome after transplantation. We were also unable to demonstrate differences in outcome between proliferative and nonproliferative forms of the disease, in agreement with previous data [2,29], although small patient numbers limited the power of the analysis. It is of note that in the patient cohort that 717

6 D. M. B. Kerbauy et al. Table 4. Causes of Death Cause of Death No. Patients (%) Relapse 10 (23) Graft failure 1 (2) Multiorgan failure 5 (12) Pneumonia/pulmonary hemorrhage GVHD 5 (12) Viral infection GVHD 3 (7) Intracranial bleed 1 (2) GVHD indicates graft-versus-host disease. formed the basis for the recently proposed MDAPS, there was a trend for shorter survival among patients with leukocytosis (indicative of proliferative features), but no differences were observed in regard to the risk of evolution into acute leukemia. In this analysis, the MDAPS score was not statistically significantly associated with outcome, although results were suggestive for relapse and overall survival. Because several conditioning regimens were used in our study, results need to be interpreted with caution. Nevertheless, if confirmed, the results would suggest that HCT should be offered to CMML patients earlier (lowerrisk categorization) rather than later in the disease course. HCT seems to offer outcomes that are better than what is achievable with nontransplantation therapy; when compared with the data that formed the basis for the MDAPS proposal, the life expectancies with HCT were superior in all patients with CMML, except possibly for those in the lowest MDAPS group, who had a median survival of 24 months. Comorbid conditions, which are more frequent in older patients, are not reflected in any of the currently used classification schemes for myelodysplastic and myeloproliferative disorders. However, they seem to have a significant negative effect on posttransplantation outcomes in patients with CMML, as previously Figure 1. Relapse-free survival. Eighteen patients are alive without relapse; 5 of the 18 have been followed up for 9.6 to 14.1 years after transplantation and are indicated as censored at 9 years (censored patients are indicated by tick marks). Figure 2. Probability of survival according to the hematopoietic cell transplantation specific comorbidity index (HCT-SCI). Patients with scores of 0 to 2 (solid lines) were compared with patients with scores of 3 to 6 (dotted line; 1 patient could not be scored because of incomplete data). Four patients with scores of 0 to 2 are alive at 9.6 to 14.1 years, and 1 patient with a score of 3 to 6 is alive at 12.2 years. These patients are indicated as censored at 9 years in the figure. observed in other disease categories [30,31]. The HCT-SCI has shown higher sensitivity in capturing comorbidities and has more predictive power for mortality among patients given myeloablative HCT than the original Charlson comorbidity index [12,13]. Patients with comorbidity scores of 3 had a very high rate of mortality. The use of this HCT-specific index may thus be useful to identify patients who are at high risk of posttransplantation mortality and may assist in Table 5. Individual Organ Comorbidities among Patients with Scores of 3 as Assessed by the Hematopoietic Cell Transplantation Specific Comorbidity Index (HCT-SCI) [12,13] Patient No. HCT-SCI Comorbidities Mild elevation of LFTs; moderate impairment of PFTs Mild elevation of LFTs; moderate impairment of PFTs Severe impairment of PFTs Severe impairment of PFTs Severe impairment of PFTs Rheumatologic disease; obesity Severe impairment of PFTs Severe impairment of PFTs Mild elevation of LFTs; severe impairment of PFTs Severe impairment of PFTs; infection Mild elevation of LFTs; severe impairment of PFTs; infection Mild elevation of LFTs; severe impairment of PFTs; arrhythmia; low ejection fraction Myocardial infarction; severe impairment of PFTs; peptic ulcer LFTs indicates liver function tests; PFTs, pulmonary function tests. 718

7 Allogeneic Transplants for CMML the selection of high-risk patients for different transplantation regimens. No conclusions in this respect can be drawn from this study, because only 2 patients were conditioned with reduced-intensity (nonmyeloablative) regimens. One of these patients died with relapse, and 1 is surviving in remission. In summary, despite remaining problems, allogeneic HCT is currently the only treatment option with curative potential for CMML. It resulted in estimated overall and relapse-free survival at 4 years of 41% (54% for patients without major comorbidities). The use of additional clinical or laboratory data, such as the MDAPS and the HCT-SCI, should help in arriving at decisions about the optimal timing of HCT and the selection of appropriate conditioning regimens. ACKNOWLEDGMENTS We thank the transplant teams for their services; Joanne Greene for maintaining the database; Eileen Bryant, PhD, for providing cytogenetic information; and Helen Crawford, Bonnie Larson, and Sue Carbonneau for help with manuscript preparation. This work was supported in part by National Institutes of Health grant nos. HL36444, CA18029, CA15704, CA78902, and CA D.M.B.K. was supported by a grant from Fundação Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Brazil) and by the Oncology Research Faculty Development Program of the Office of International Affairs of the National Cancer Institute. M.L.S. was supported in part by a grant from the Oncology Research Faculty Development Program of the Office of International Affairs of the National Cancer Institute. J.M.P. is recipient of a Lymphoma Research Foundation Career Development Award. REFERENCES 1. Vardiman JW, Harris NL, Brunning RD. 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