Scholarly article on topic 'Infused CD34+ cell dose predicts long-term survival in acute myelogenous leukemia patients who received allogeneic bone marrow transplantation from matched sibling donors in first complete remission'

Infused CD34+ cell dose predicts long-term survival in acute myelogenous leukemia patients who received allogeneic bone marrow transplantation from matched sibling donors in first complete remission Academic research paper on "Clinical medicine"

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Abstract of research paper on Clinical medicine, author of scientific article — Se-Hoon Lee, Mark H. Lee, Je-Hwan Lee, Yoo Hong Min, Kyoo-Hyung Lee, et al.

Abstract Allogeneic stem cell transplantation (ASCT) has improved the outcome of acute myelogenous leukemia (AML). To further improve the treatment outcome of ASCT in AML, finding a modifiable prognostic factor is mandatory. We evaluated the effect of CD34+ cell dose on survival in allogeneic bone marrow transplantation (BMT) from HLA-matched sibling donors for AML patients in first complete remission (CR1). The 99 patients included in our analysis were classified into high CD34+ cell dose group (CD34+ cells ≥ 2.5 × 106/kg) and low CD34+ cell dose group (CD34+ cells < 2.5 × 106/kg). The high CD34+ cell dose patients had better overall survival (5-year overall survival rate, 75% ± 6% vs 52% ± 9%; P = .01) and leukemia-free survival (5-year leukemia-free survival rate, 70% ± 6% vs 44% ± 9%; P = .04). CD34+ cell dose was the only independent prognostic factor in overall survival and leukemia-free survival. The high CD34+ cell dose group had a lower relapse incidence with a borderline statistical significance (5-year relapse rate, 27% ± 6% vs 50% ± 10%; P = .09). There were no differences in the engraftment of neutrophil and platelet, grade II-IV acute graft-versus-host disease (GVHD), extensive-stage chronic GVHD, and transplant-related mortality between the high and low CD34+ cell dose groups. We confirmed that high CD34+ cell dose favorably affects the outcomes in allogeneic BMT for AML. The effort to attain a high CD34+ cell dose should be pursued during bone marrow harvest in allogeneic BMT for AML in CR1.

Academic research paper on topic "Infused CD34+ cell dose predicts long-term survival in acute myelogenous leukemia patients who received allogeneic bone marrow transplantation from matched sibling donors in first complete remission"

Biology of Blood and Marrow Transplantation 11:122-128 (2005) © 2005 American Society for Blood and Marrow Transplantation l083-879l/05/ll02-0007$30.00/0 doi:l0.l0l6/j.bbmt.2004.ll.0l8

AS BMI

American Society for Blood and Marrow Transplantation

Infused CD34+ Cell Dose Predicts Long-Term Survival in Acute Myelogenous Leukemia Patients Who Received Allogeneic Bone Marrow Transplantation From Matched Sibling Donors in First Complete Remission

Se-Hoon Lee,1 Mark H. Lee,2 Je-Hwan Lee,3 Yoo Hong Min,4 Kyoo-Hyung Lee,3 June-Won Cheong,4 Jeeyun Lee,1 Keon Woo Park,1 Jung Hun Kang,1 Kihyun Kim,1 Won Seog Kim,1 Chul Won Jung,1 Seong-Jun Choi,3 Jung-Hee Lee,3 Keunchil Park1

1Division of Hematology and Oncology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea; 2Division of Hematology and Oncology, Department of Internal Medicine, The Brody School of Medicine, Greenville, North Carolina; 3Division of Hematology and Oncology, Department of Medicine, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea; and 4Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea

Correspondence and reprint requests: Mark H. Lee, MD, Division of Hematology and Oncology, Department of Internal Medicine, The Brody School of Medicine, 3E-127 Brody Medical Sciences Building, 600 Moye Boulevard, Greenville, NC 27858 (e-mail: leema@mail.ecu.edu).

Received September 19, 2004; accepted November 10, 2004

ABSTRACT

Allogeneic stem cell transplantation (ASCT) has improved the outcome of acute myelogenous leukemia (AML). To further improve the treatment outcome of ASCT in AML, finding a modifiable prognostic factor is mandatory. We evaluated the effect of CD34+ cell dose on survival in allogeneic bone marrow transplantation (BMT) from HLA-matched sibling donors for AML patients in first complete remission (CR1). The 99 patients included in our analysis were classified into high CD34+ cell dose group (CD34+ cells > 2.5 X 106/kg) and low CD34+ cell dose group (CD34+ cells < 2.5 X 106/kg). The high CD34+ cell dose patients had better overall survival (5-year overall survival rate, 75% ± 6% vs 52% ± 9%; P = .01) and leukemia-free survival (5-year leukemia-free survival rate, 70% ± 6% vs 44% ± 9%; P = .04). CD34+ cell dose was the only independent prognostic factor in overall survival and leukemia-free survival. The high CD34+ cell dose group had a lower relapse incidence with a borderline statistical significance (5-year relapse rate, 27% ± 6% vs 50% ± 10%; P = .09). There were no differences in the engraftment of neutrophil and platelet, grade II-IV acute graft-versus-host disease (GVHD), extensive-stage chronic GVHD, and transplant-related mortality between the high and low CD34+ cell dose groups. We confirmed that high CD34+ cell dose favorably affects the outcomes in allogeneic BMT for AML. The effort to attain a high CD34+ cell dose should be pursued during bone marrow harvest in allogeneic BMT for AML in CR1. © 2005 American Society for Blood and Marrow Transplantation

KEY WORDS

Allogeneic BMT • Acute myelogenous leukemia • CD34+ cell dose

INTRODUCTION

Allogeneic stem cell transplantation (ASCT) has improved the treatment outcome of acute myelogenous leukemia (AML) in first complete remission (CR1) with evidence of a beneficial graft-versus-leu-

kemia effect [1]. To improve the outcome after ASCT for AML in CR1, efforts have been made to find the prognostic factors. The following prognostic factors have been found to have some possibility of predicting survival: age, sex, prior hepatitis, duration of symptoms at the time of presentation [2], acute graft-ver-

sus-host disease (GVHD), interstitial pneumonia, presenting white blood cell (WBC) count [3], number of induction therapies needed to achieve CR, shorter time to attain CR [4], earlier time from diagnosis to ASCT [5], and cytogenetics [6,7]. These potentially significant prognostic factors cannot be modified, and modifiable factors such as pretransplantation consolidation therapy [8], preparatory regimen [9], GVHD prophylaxis [10], and ASCT cell source [11-13] have not shown consistent and significant differences in overall outcome.

Infused cell dose, one of the modifiable factors, has raised interest as a potential prognostic factor in ASCT for AML in CR1. The clinical relevance of total nucleated cell (TNC) number during ASCT was identified earlier in aplastic anemia [14]. TNC number has been shown to predict survival of patients with hematologic malignancies [15-20].

CD34 has been used as a surrogate marker of hematopoietic stem cells. Several studies have investigated the prognostic role of CD34+ cell dose during ASCT in AML. Some studies have explored CD34+ in specific settings, such as T-cell-depleted transplantation [21,22] and human leukocyte antigen (HLA) haplo-identical-related donor transplantation [23]. Other studies included heterogeneous patients in terms of disease (eg, AML, acute lymphocytic leukemia [ALL], chronic myelocytic leukemia [CML]) and the risk of disease (ie, standard vs high) [24-26].

In the present study, we analyzed 99 patients with AML in CR1 who underwent allogeneic BMT from HLA-identical sibling donors, to study the association between CD34+ cell dose and clinical outcome.

MATERIALS AND METHODS

Data Collection and Patient Selection

Our study group included all patients fulfilling the following criteria in 3 institutions: (1) AML in CR1, (2) unmanipulated BMT, (3) HLA-identical sibling donor, (4) transplantation between March 1992 and January 2003, and (5) flow cytometry analysis of CD34+ cells.

Definition of Endpoints

Hematopoietic recovery. Neutrophil and platelet recoveries were analyzed separately and defined by an absolute neutrophil count (ANC) > .5 X 109/L for 3 consecutive days and a platelet count > 50 X 109/L for 7 consecutive days with no platelet support, respectively. The median time to recovery was calculated using the product-limit method.

Survival. Overall survival (OS) was defined as the time interval from transplantation to death of any cause. Leukemia-free survival (LFS) was defined as the time interval from transplantation to the first event

(either relapse or death in CR). Transplant-related mortality (TRM) was defined as death in continuous CR, and relapsed patients were censored at the time of relapse.

GVHD. Acute GVHD (aGVHD) was diagnosed and graded at each transplantation center according to the Seattle criteria [27]. Only patients with grade II and higher were considered to have significant aGVHD. Chronic GVHD (cGVHD) was defined according to standard criteria (limited and extensive) [28]. Patients surviving without relapse for > 100 days after transplantation with sustained donor engraft-ment were considered assessable for cGVHD.

CD34+ Cell Enumeration

Flow cytometry was used to determine CD34+ cell count. Leukocytes were prepared from fresh bone marrow using ammonium chloride lysis. The leukocytes were incubated with pretitered antibody, washed twice, and acquired using FACSort (Becton Dickinson, Franklin Lakes, NJ) or FACSCalibur (Becton Dickinson) with CELLQUEST software.

Statistical Analysis

All analyses were performed using the SPSS statistical analysis program (SPSS, Chicago, IL). Quantitative variables were reported as median and range. The following patient and graft characteristics were analyzed for their potential prognostic value on outcome: center, patient and donor characteristics (age, sex, and sex matching), disease factors (WBC count at diagnosis, French-American-British [FAB] classification, interval from diagnosis to CR1, interval from CR1 to transplantation, cytogenetic group [29]), and transplant-related factors (CD34+ cell dose infused per kilogram of recipient body weight, year of transplantation, nature of the conditioning regimen including total body irradiation [TBI] or not, GVHD prophylaxis). For these prognostic analyses, continuous variables were categorized according to the median value, except for CD34+ cell count. We analyzed data with various discriminating CD34+ cell levels (.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, and 5.0). All CD34+ cell dose levels showed superior OS and LFS in the higher cell dose group than in the lower cell dose group with various degrees of statistical significance, sometimes reaching statistical significance and sometimes not. We also analyzed data using the median as the discriminating point and obtained the same results reaching statistical significance. When quartiles were used, the higher CD34+ cell dose group demonstrated a trend toward superior OS and LFS (4th > 3rd > 2nd > 1st quartiles). We concluded that 2.5 X 106/kg is the most discriminating point after the repetitive analyses with variable cell dose discriminating

Table 1. Patient Characteristics Characteristics Low (n = 37) High (n = 62) P Value

Center .11

Center 1 8 (22%) 9 (15%)

Center 2 16 (43%) 40 (64%)

Center 3 13 (35%) 13 (21%)

Age (years) .42

Median (range) 34 (15-47) 34.5 (16-48)

Sex .09

Female 15 (40%) 36 (58%)

Sex matching .66

Female to male 7 (19%) 14 (23%)

Others 30 (81%) 48 (77%)

Age of donor (years) .91

Median (range) 30 (14-51) 33.5 (13-55)

WBC count at diagnosis (X I09 L) .81

Median (range) 13.5 (.9-344.6) 11.4 (.6-141.6)

FAB classification .29

MI/M2/M4 32 (86%) 58 (93%)

M5/M6/M7 5 (14%) 4 (7%)

Interval from diagnosis to CRI (d) .26

Median (range) 31.5 (14-105) 38 (14-105)

Interval from CRI to BMT (d) .96

Median (range) 96 (8-454) 90 (20-365)

Cytogenetics 1.00

Favorable 6 (17%) 10 (16%)

Intermediate 18 (51%) 31 (51%)

Unfavorable 8 (23%) 15 (25%)

Unknown 3 (9%) 5 (8%)

Year of BMT .01

1992-1998 22 (59%) 21 (34%)

1999-2003 15 (41%) 41 (66%)

Conditioning .02

No TBI 17 (46%) 43 (69%)

TBI 20 (54%) 19 (31%)

GVHD prophylaxis .12

CSA only 2 (5%) 11 (18%)

CSA+ MTX 35 (95%) 51 (82%)

CSA, cyclosporine A; MTX, methotrexate.

points, although we cannot know the accurate, biologically relevant number.

To compare the distribution between the subgroups of patients, the x2 test was used for categorical variables and the nonparametric Mann-Whitney U test was used for continuous variables. The probabilities of OS, LFS, and TRM were estimated by the product-limit method. The significance of differences between curves was estimated using the log-rank test. All variables associated with outcome with a P value < .1 in univariate analyses and all characteristics significantly statistically different (P < .05) between subgroups of patients were included in a multivariate analysis. All multivariate analyses were adjusted on center.

RESULTS

Patient Characteristics

We collected patients satisfying the previously defined eligible criteria from 3 transplantation centers. A total of 99 patients with AML in CR1 were treated

with allogeneic BMT from sibling full-matched donors during the study period. Data on CD34+ cell count were available for all patients included in this analysis.

The range of CD34+ cell count was .1 to 18.2 X 106/kg (median, 3.1 X 106/kg). Table 1 gives the characteristics of patients receiving allogeneic BMT with low (< 2.5 X 106/kg) versus high (> 2.5 X 106/kg) CD34+ cell dose. Patients with high CD34+ cell dose underwent allogeneic BMT more often during the recent period (P = .01) and more frequently received non-TBI conditioning regimens (P = .02).

Hematologic Recovery

Times to recovery of both neutrophils and platelets were similar with low and high CD34+ cell doses. All patients in both groups achieved ANC > .5 X 109/L; however, 2 patients (5%) from the low CD34+ cell dose group and another 2 patients (3%) from the high CD34+ cell dose group failed to achieve an untransfused platelet count > 50 X 109/L (P = .63). The median time to achieve ANC > .5 X 109/L was

Overall survival (months)

Figure 1. Overall survival according to CD34+ cell dose.

15 days (range, 10-24) for the low CD34+ cell dose group and 14 days (range, 10-21) for the high CD34+ cell dose group (P = .16). The median time to achieve an untransfused platelet count > 50 X 109/L was 30 days (range, 12-169) for the low CD34+ cell dose group and 27 days (range, 15-151) for the high CD34+ cell dose group (P = .27).

Overall Survival

A total of 32 patients died of various causes. The estimated OS at 5 years for the low CD34+ cell dose and high CD34+ cell dose groups was 52% ± 9% and 75% ± 6%, respectively (P = .01) (Figure 1). Female sex of the recipient favorably influenced OS (P = .05) and unfavorable cytogenetics unfavorably influenced OS with a borderline statistical significance (P = .09) in univariate analysis. In multivariate analysis, CD34+ cell dose was the only independent prognostic factor in OS (Table 2).

Table 2. Results of Multivariate Analysis for OS and LFS Outcomes and Variables HR (95% CI) P Value

CD34+ > 2.5 X l06/kg .4 (.2-.9) .03

Center - .82

Sex - .l2

Cytogenetics - .08

Year of BMT - .92

TBI - .92

CD34+ > 2.5 X l06/kg .5 (.3-1.0) .05

Center - .80

Sex - .25

Year of BMT - .40

TBI - .35

CI, confidence interval; HR, hazard ratio.

Figure 2. Leukemia-free survival according to CD34+ cell dose. Leukemia-Free Survival

A total of 30 patients relapsed, and 7 patients died of nonleukemic causes. The estimated LFS at 5 years for the low CD34+ cell dose and high CD34+ cell dose groups was 44% ± 9% and 70% ± 6%, respectively (P = .04) (Figure 2). Female sex of the recipient (P = .10) was associated with a favorable LFS with a borderline statistical significance in univariate analysis (P = .10). In multivariate analysis, CD34+ cell dose was the only independent prognostic factor in LFS (P = .05) (Table 2).

Treatment-Related Mortality

A total of 7 patients died of nonleukemic causes. In the low CD34+ cell dose group, the causes of TRM were interstitial pneumonia in 2 patients (at 2.7 and 2.9 months), veno-occlusive disease (VOD) in 1 patient (at 1.5 months), and hepatic failure in 1 patient (at 11 months). In the high CD34+ cell dose group, the causes of TRM were interstitial pneumonia in 1 patient (at 1.7 months), gastrointestinal bleeding in 1 patient (at 1.5 months), and VOD in 1 patient (at 2 months). There was no significant difference in TRM between the low CD34+ cell dose and high CD34+ cell dose groups (P = .27) (Figure 3).

Relapse

A total of 30 patients relapsed. The estimated relapse rate (RR) at 5 years for the low CD34+ cell dose and high CD34+ cell dose groups was 50% ± 10% and 27% ± 6%, respectively (P = .09) (Figure 4). No other prognostic factors demonstrated statistically significant differences in RR in univariate analysis.

The low and high CD34+ cell dose groups did not differ in terms of risk of grade II-IV aGVHD. The

CD34+ < 2.5 x 106/kg

(J CD34+ > 2.5 x 106/kg

P= 0.27

0 20 40 60 80 100

Time since BMT (months)

Figure 3. Transplant-related mortality according to CD34+ cell dose. BMT indicates bone marrow transplantation.

incidence of grade II-IV aGVHD for the 2 groups was 16% and 8%, respectively (P = .32). There was no difference in the incidence of extensive-stage cGVHD between the low CD34+ cell dose group (15%) and the high CD34+ cell dose group (19%) (P = .63).

DISCUSSION

We conclude that high CD34+ cell dose is an independent prognostic factor for OS and LFS for AML patients in CR1 undergoing allogeneic BMT. We took 2.5 X 106/kg as a CD34+ cell dose threshold to differentiate the 2 CD34+ cell dose groups. The median CD34+ cell dose was 3.1 X 106/kg, but a CD34+ cell dose of 2.5 X 106/kg, if taken as a threshold for grouping these patients, produced a better delineation of outcome variables.

A previous study [20] reported the relevance of total nucleated cell (TNC) dose in the same setting, that is, AML, CR1 allogeneic BMT from an HLA full-matched sibling. That study showed that high TNC dose (> 2.6 X 108/kg) was correlated with better LFS and that better LFS resulted from a lower TRM and lower relapse incidence in the high TNC dose group. The authors reported 5-year LFSs of 46% and 68% in the low and high TNC dose groups, respectively. Similarly, our results showed 5-year LFSs of 44% and 70% in the low and high CD34+ cell dose groups, respectively (P = .04).

The classical concept of cell dose in allogeneic BMT has been limited to engraftment and rapidity of cell recovery. A study of aplastic anemia demonstrated that high TNC dose reduced the incidence of graft rejection [14]. A study of AML also focused on early mortality [15]. Other studies of hematologic malignancies with or without nonmalignancies showed that

higher bone marrow TNC dose was correlated with decreased deep fungal infection [17], decreased severe aGVHD and aGVHD-related mortality [16,18,19], and less nonleukemic death and better LFS [19]. The aforementioned studies focused on reduced nonleuke-mic mortality from rapid cell recovery and decreased risk of severe infection with higher bone marrow TNC dose. In addition to nonleukemic mortality, the European Bone Marrow Transplantation study group reported that a decreased relapse incidence in AML was associated with higher bone marrow TNC dose [20].

Our trial is the first report of the relevance of CD34+ cell dose in allogeneic BMT in a homogeneous AML patient group. Higher CD34+ cell dose definitely improved LFS (P = .04) and OS (P = .01). Whether improved outcome in this study resulted from either decreased relapse mortality or decreased nonrelapse mortality cannot be answered. Although decreased relapse incidence and TRM were observed in the high CD34+ cell dose group, the differences did not reach statistical significance (P = .09 and P = .20, respectively). The failure to reach statistical significance was possibly due to the relatively small sample size.

The relevance of CD34+ cell dose in allogeneic BMT was evaluated in heterogeneous patient groups [25,26]. These trials demonstrated that higher CD34+ cell dose was associated with lower TRM and better OS. A study of CD34+ cell dose in BMT for various risk groups of hematologic malignancies showed that improved LFS was due to decreased TRM but not decreased relapse rate, in contrast to peripheral stem cell transplantation [26]. Other studies reported that higher CD34+ cell dose in peripheral stem cell transplantation showed a detrimental

<]) .3

0 20 40 60 80 100 Time since BMT (months)

Figure 4. Relapse incidence according to CD34+ cell dose. BMT indicates bone marrow transplantation.

effect by increasing TRM, especially higher cGVHD-associated mortality [30,31]. The mechanism underlying the different effects of CD34+ cell dose according to stem cell source should be the subject of future investigation.

We confirmed that higher CD34+ cell dose infusion in BMT from matched sibling donors for AML in CR1 improved OS and LFS. Our results suggest that real-time determination of CD34+ count and an effort to collect higher CD34+ cell doses should be done in this setting. But it remains uncertain whether the beneficial effect of higher CD34+ cell dose could be extended to the unrelated donor scenario, because the accurate mechanism of this effect was not determined.

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