Outcome of allogeneic hematopoietic stem cell transplantation for childhood acute lymphoblastic leukemia in second complete remission: a single institution study.

Abstract

The survival rate for childhood acute lymphoblastic leukemia (ALL) has improved significantly. However, overall prognosis for the 20 to 25% of patients who relapse is poor, and allogeneic hematopoietic stem cell transplantation (HSCT) offers the best chance for cure. In this study, we identified significant prognostic variables by analyzing the outcomes of allogeneic HSCT in ALL patients in second complete remission (CR).
Fifty-three ALL patients (42 men, 79%) who received HSCT in second CR from August 1991 to February 2009 were included (26 sibling donor HSCTs, 49%; 42 bone marrow transplantations, 79%). Study endpoints included cumulative incidence of acute and chronic graft-versus-host disease (GVHD), relapse, 1-year transplant-related mortality (TRM), disease-free survival (DFS), and overall survival (OS).
Cumulative incidences of acute GVHD (grade 2 or above) and chronic GVHD were 45.3% and 28.5%, respectively. The estimated 5-year DFS and OS for the cohort was 45.2±6.8% and 48.3±7%, respectively. Only donor type, i.e., sibling versus unrelated, showed significant correlation with DFS in multivariate analysis (P=0.010). The rates of relapse and 1 year TRM were 28.9±6.4% and 26.4±6.1%, respectively, and unrelated donor HSCT (P=0.002) and HLA mismatch (P=0.022) were significantly correlated with increased TRM in univariate analysis.
In this single institution study spanning more than 17 years, sibling donor HSCT was the only factor predicting a favorable result in multivariate analysis, possibly due to increased TRM resulting from unrelated donor HSCT.

Full text

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http://dx.doi.org/10.3345/kjp.2012.55.3.100
Korean J Pediatr 2012;55(3):100-106
Original article
100
Outcome of allogeneic hematopoietic stem cell
transplantation for childhood acute lymphoblastic
leukemia in second complete remission: a single
institution study
Purpose: The survival rate for childhood acute lymphoblastic leukemia
(ALL) has improved significantly. However, overall prognosis for the 20
to 25% of patients who relapse is poor, and allogeneic hematopoietic
stem cell transplantation (HSCT) offers the best chance for cure. In
this study, we identified significant prognostic variables by analyzing
the outcomes of allogeneic HSCT in ALL patients in second complete
remission (CR).
Methods: Fifty-three ALL patients (42 men, 79%) who received HSCT
in second CR from August 1991 to February 2009 were included (26
sibling donor HSCTs, 49%; 42 bone marrow transplantations, 79%).
Study endpoints included cumulative incidence of acute and chronic
graft-versus-host disease (GVHD), relapse, 1-year transplant-related
mortality (TRM), disease-free survival (DFS), and overall survival (OS).
Results: Cumulative incidences of acute GVHD (grade 2 or above) and
chronic GVHD were 45.3% and 28.5%, respectively. The estimated
5-year DFS and OS for the cohort was 45.2±6.8% and 48.3±7%,
respectively. Only donor type, i.e., sibling versus unrelated, showed
significant correlation with DFS in multivariate analysis (P=0.010). The
rates of relapse and 1 year TRM were 28.9±6.4% and 26.4±6.1%,
respectively, and unrelated donor HSCT (P=0.002) and HLA mismatch
(P=0.022) were significantly correlated with increased TRM in
univariate analysis.
Conclusion: In this single institution study spanning more than 17 years,
sibling donor HSCT was the only factor predicting a favorable result
in multivariate analysis, possibly due to increased TRM resulting from
unrelated donor HSCT.
Key words: Acute lymphoblastic leukemia, Child, Second complete
remission, Transplantation
Eun-Jung Lee, MD, Ji Yoon Han, MD, Jae
Wook Lee, MD, Pil-Sang Jang, MD, PhD,
Nack-Gyun Chung, MD, PhD, Dae-Chul
Jeong, MD, PhD, Bin Cho, MD, PhD, Hack-Ki
Kim, MD, PhD
Department of Pediatrics, The Catholic University of
Korea, School of Medicine, Seoul, Korea
Received: 15 September 2011, Revised: 31 October 2011
Accepted: 14 November 2011
Corresponding author: Bin Cho, MD, PhD
Department of Pediatrics, Seoul St. Mary’s Hospital, The
Catholic University of Korea School of Medicine, 222 Ban-
po-daero, Seocho-gu, Seoul 137-701, Korea
Tel: +82-2-2258-6187, Fax: +82-2-588-3589
E-mail: chobinkr@catholic.ac.kr
Copyright © 2012 by The Korean Pediatric Society
This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-
nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Korean J Pediatr 2012;55(3):100-106 • http://dx.doi.org/10.3345/kjp.2012.55.3.100
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Introduction
Despite major improvements in the overall survival of children
with acute lymphoblastic leukemia (ALL), for the 20 to 25% of
patients who relapse, the prognosis remains poor1). Notwithstanding
its potential complications, allogeneic hematopoietic stem cell
transplantation (HSCT), preferably from a matched sibling
donor (MSD), is known to result in better outcome rather than
chemotherapy only in second complete remission (CR)2-4). With
improvements in human leukocyte antigen (HLA) typing and
supportive care of transplant-related complications, recent evidence
suggests similar outcomes when comparing the results of MSD HSCT
and matched unrelated (MUD) HSCT5-7). However, most of the pa-
tients undergoing transplantation will fail to be cured of their disease,
emphasizing the need to identify important prognostic factors in
children who receive HSCT, as well as novel therapeutic modalities.
Previous analyses indicate that the duration of first remission has
overall prognostic significance for children with ALL who receive
allogeneic HSCT after first relapse6,7). Other important factors
include the conditioning regimen utilized as well as the disease status
at the time of transplantation8,9). Efforts to identify other signifi cant
prognostic variables are key to maximizing the efficacy of al lo geneic
HSCT in childhood ALL, and improve upon its current shortcomings.
In this study, we retrospectively reviewed the results of allogeneic
HSCT undertaken in children with ALL in second CR, during a
period spanning more than 17 years at a single institution, with the
aim of summarizing overall therapeutic outcome for these children,
identifying major prognostic variables, and comparing our institution
results for MSD HSCT and MUD HSCT.
Materials and methods
1. Patient cohort
1) Pre-transplantation
Patients diagnosed with ALL, who received allogeneic HSCT
in second CR from August, 1991 to February, 2009 at the
Department of Pediatrics, The Catholic University of Korea, were
included. Recipients of cord blood transplantation or familial donor
transplantation with 1 antigen or more mismatches were excluded
from the study group. Overall, 53 patients (42 male, 79%) formed the
study cohort (Table 1). Median age at diagnosis was 6.5 years (range,
0.3 to 15 years). Risk group classification before 2001 derived from
National Cancer Institute criteria, and then, subsequent to 2001, was
based on previously published institutional criteria10). Twenty patients
(38%) were classified as low or standard risk ALL, and 33 (62%)
were classified as high or very high risk ALL. Of 41 patients with
available cytogenetic studies at diagnosis, 8 had high risk features
including 4 patients with BCR-ABL1, 3 with E2A-PBX1, and 1
patient with MLL gene rearrangement.
All patients in the study cohort were diagnosed with first bone
marrow relapse at a median of 32.6 months since achieving CR (range
1.1 to 118) (Table 2). For the purposes of risk stratification according
to duration of first CR, patients were categorized into early relapse
(<12 months since CR, n=11, 21%), intermediate relapse (≥12 months
and <36 months since CR, n=18, 34%), and late relapse groups (≥36
months since CR, n=24, 45%)7).
2) Transplantation
All patients underwent allogeneic HSCT after having achieved
second CR (Table 3). Median age at transplantation was 9.7 years
(range, 0.9 to 20.7 years). Similar numbers of sibling donor and un-
related donor transplantations were included (26 sibling, 49%; 27
unrelated HSCTs, 51%), but with regards to cell source, a far greater
number of bone marrow transplantations (BMT) were included than
granulocyte-colony stimulating factor mobilized peripheral blood
stem cell transplantations (PBSCT) (42 BMTs, 79%; 11 PBSCTs,
21%).
As the study covered HSCTs undertaken during a lengthy period
in time, HLA typing for the study cohort was also done with varying
Table 1. Patient Characteristics at Initial Diagnosis (n=53)
Characteristic
Median age (yr)
Gender
Male
Female
Median WBC count (/mm
Risk group
Low or standard
High or very high
Values are presented as median (range) or number (%).
WBC, white blood cell
Value
6.5 (0.3-15)
42 (79)
11 (21)
3) 11,500 (880-306,500)
20 (38)
33 (62)
Table 2. Patient Characteristics at First Relapse (n=53)
Characteristic
Age (yr)
WBC count (/mm
Time from CR to relapse (mo)
Early (<12)
Intermediate (≥12, <36)
Late (≥36)
Values are presented as median (range) or number (%).
CR, complete remission; WBC, white blood cell.
Value
9.2 (0.6-20.3)
5,080 (900-242,000)
32.6 (1.1-118)
11 (21)
18 (34)
24 (45)
3)

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EJ Lee, et al. • Outcome of HSCT for childhood ALL in second CR
methodologies. Different modes of HLA typing posed a problem
concerning patient classification according to HLA compatibility. A
strict definition of “HLA-match” as an 8 of 8 allele complete match
of high resolution-typed HLA, as is done currently in our institution,
would classify many patients who underwent HSCT with a
serologically matched donor, previous to implementation of high
resolution typing, as having received “HLA-mismatched” transplanta-
tions. In order to resolve this issue, all patients were categorized
according to time-appropriate HLA methodology; that is, an “HLA-
match” was defined as a complete match of HLA tested between
donor and recipient at that point in time, be the method serologic or
molecular.
All but 2 patients received a total body irradiation (TBI)-based
conditioning regimen, with TBI-cytarabine-cyclophosphamide±anti-
thymocyte globulin (ATG) being the most commonly utilized regimen
(n=31, 59%), followed by TBI-cyclophosphamide (n=15, 28%).
Regimens without TBI included 1 busulfan-based and 1 carmustine-
based conditioning each. Graft-versus-host disease (GvHD) prophy-
laxis consisted of cyclosporine and mini dose methotrexate (MTX)
for 49 patients (92%), with the remaining patients receiving a com-
bination of cyclosporine and mycophenolate mofetil±MTX.
2. Study endpoints
Major study endpoints included engraftment, incidence of acute
GvHD (grades II to IV) and chronic GvHD, disease-free survival
(DFS) and overall survival (OS). Neutrophil engraftment was defined as
the first of 3 consecutive days in which the absolute neu trophil count
(ANC) was >1,000/mm3, and platelet engraftment was defined as the
first of 3 consecutive days in which the platelet count was > 50,000/
mm3 with no platelet transfusions in the past seven days. Acute and
chronic GvHD were classified according to previously established
criteria11,12). DFS was defined as the time from HSCT till relapse or
death, whichever came first. OS was defined as time from HSCT
till death from any cause. Relapse rate and rate of 1-year transplant-
related mortality (TRM) were also evaluated.
3. Statistical analyses
Prognostic factors for DFS were evaluated using Cox proportional
hazards regression model. The following variables were analyzed: age
at initial diagnosis, age at transplant, patient gender, white blood cell
(WBC) count at diagnosis, WBC count at relapse, initial risk group,
duration of first CR, donor type, cell source, HLA compatibility,
ABO compatibility, and conditioning regimen. Variables with a P
value of <0.1 on univariate study were entered in a multivariate model
using the backward stepwise selection method. Incidence of acute
and chronic GvHD, relapse and TRM rates were calculated using
a cumulative incidence function with consideration of competing
risks. Variables studied for DFS were also evaluated for contributing
to acute and chronic GvHD, relapse rate and TRM rate using Gray’s test.
Again, factors with a P value of <0.1 were analyzed in a multivariate
manner using Fine and Gray’s proportional hazards model. DFS and
OS were calculated with the Kaplan-Meier method and comparisons
done with the log rank test. P values<0.05 were considered statistically
significant. Statistical work was done on SPSS ver. 12.0 (SPSS Inc.,
Chicago, IL, USA) and R package, ver. 2.10.1 (available from: http://
cran.r-project.org).
Results
1. Engraftment data
Median infused cell counts were as follows: TNC 2.6×108/kg
(range, 0.7 to 42.1×108/kg), MNC 1.2×108/kg (range, 0.5 to 35.7×
108/kg), CD34+ 5.3×106/kg (range, 0.6 to 81.4×106/kg), CD3+
Table 3. Transplantation Characteristics (n=53)
Characteristic
Age at transplant (yr)
Donor type
Sibling
Unrelated
Cell source
BM
PBSC
Donor age (yr)
HLA compatibility*
Match
Mismatch
Donor-recipient gender
Female-male
Others
ABO compatibility
Match
Mismatch
Conditioning regimen
TBI-Ara-Cy±ATG
Others
GvHD prophylaxis
CS+MTX
Others
Values are presented as median (range) or number (%).
BM, bone marrow; PBSC, G-CSF-mobilized peripheral blood stem cells;
HLA, human leukocyte antigen; TBI, total body irradiation; Ara, cytarabine;
Cy, cyclophosphamide; ATG, anti-thymocyte globulin; GvHD, graft-versus-
host disease; CS, cyclosporine; MTX, methotrexate.
*HLA match includes either low or high resolution HLA match.
Value
9.7 (0.9-20.7)
26 (49)
27 (51)
42 (79)
11 (21)
20.5 (1-40)
38 (72)
15 (28)
13 (25)
40 (76)
26 (49)
27 (51)
31 (59)
22 (42)
49 (92)
4 (8)

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103
testicular relapse 9 months post-transplantation. Analysis was done
to determine factors significant for relapse using the variables utilized
for study of DFS. Initial WBC count at diagnosis had prognostic
relevance bordering on significance, with patients presenting with an
5.2×107/kg (range, 0.5 to 518×107/kg). All patients showed neu-
trophil engraftment at a median of 15 days (range, 8 to 31 days), while
only 38 patients (72%) showed full recovery of platelet count to greater
than 50,000/mm3 at a median of 26 days (range, 10 to 178 days) post-
transplantation.
2. Incidence of acute and chronic GvHD
Acute GvHD of grade II or above was diagnosed in 24 patients
at a median of 15 days post-transplantation (range, 5 to 81) for a
cumulative incidence of 45.3±6.9%. Eighteen patients (34%) were
diagnosed with grade II acute GvHD, and 3 patients each (6%) were
diagnosed with grades III and IV GvHD. All 3 patients with grade
IV GvHD died. Important risk factors for acute GvHD included age
at transplant (P=0.090), donor type (P<0.001), and HLA compatibility
(P=0.002), with only HLA compatibility having a significant effect
on multivariate study (hazard ratio [HR], 2.41; 95% confidence in-
terval [CI], 1.14 to 5.08; P=0.021).
Chronic GvHD was diagnosed in 16 patients (mild 5, 9%; moderate
10, 19%; severe 1, 2%) for a cumulative incidence of 28.5±6.3%.
Median time at chronic GvHD diagnosis was 5 months after trans-
plantation (range, 2.7 to 17.2). No one factor had a significant impact
on chronic GvHD incidence.
3. Analysis of DFS
The estimated 5-year DFS for the entire cohort was 45.2±6.8%.
On analyzing for prognostic factors for DFS, age at diagnosis (P=
0.071), donor type (P=0.010), and HLA compatibility (0.021) proved
to be important variables (Table 4). However, on multivariate study,
only donor type had prognostic significance (HR, 2.75; 95% CI, 1.28
to 5.93; P=0.010), with superior DFS in recipients from sibling donors
compared to unrelated donors. Patients with a long duration of first
CR before HSCT did not have a survival advantage compared with
patients who relapsed early.
DFS curves were redrawn in order to evaluate for potential
comparable outcomes of MSD and MUD HSCT (Fig. 1). Five-year
estimated DFS for MSD HSCT, MUD HSCT, and mismatched
unrelated donor (MMUD) HSCT were as follows: 68±9.3%, 38.5±
13.5%, 14.3±9.4% respectively. Log-rank comparison of MSD and
MUD HSCT showed a value bordering on statistically significant
difference (P=0.051), while a comparison of MSD HSCT and
MMUD HSCT showed clear differences in DFS (P=0.002).
4. Relapse and TRM incidence
Overall, 15 patients relapsed resulting in an estimated 5-year rate
of disease relapse of 28.9±6.4%. All patients showed bone marrow
(BM) relapse except for 1 patient who was diagnosed with isolated
Table 4. Univariate Study of Disease-free Survival Prognostic Factors
VariableNo. (Number)
Age at diagnosis
≥1 and <10 40
<1 or ≥10 13
Donor type
Sibling 26
Unrelated27
HLA compatibility*
Match 38
Mismatch15
Age at transplant
<10 27
≥10 26
Gender
Male 42
Female11
WBC count at diagnosis
<50,000 41
≥50,000 12
WBC count at relapse†
<10,000 34
≥10,00016
Initial risk group
Low-standard 20
High-very high33
Duration of first CR (mo)
<12 / ≥12 and <3611/18
<12 / ≥3611/24
Cell source
BM 42
PBSC11
ABO compatibility
Match 26
Mismatch27
Conditioning regimen
TBI-Ara-Cy±ATG 31
Others 22
HLA, human leukocyte antigen; WBC, white blood cell; CR, complete
remission; BM, bone marrow; PBSC, G-CSF-mobilized peripheral blood stem
cells; TBI, total body irradiation; Ara, cytarabine; Cy, cyclophosphamide; ATG,
anti-thymocyte globulin.
*HLA match includes either low or high resolution HLA match.
at relapse was unavailable in 3 patients who were initially treated and
showed first relapse at another institution, and who were subsequently
transferred to our hospital for further treatment, including HSCT.
EventsP value
0.071
20
10
0.010
10
20
0.021
17
13
0.847
15
15
0.166
26
4
0.563
22
8
0.707
19
10
0.222
9
21
7/13
7/10
0.524
0.207
0.478
23
7
0.837
14
16
0.884
19
11
†WBC count

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EJ Lee, et al. • Outcome of HSCT for childhood ALL in second CR
initial WBC count ≥50,000/mm3 more likely to relapse than those
with lower counts (P=0.082). However, no one variable had a definite
significant impact on rate of relapse, as determined by univariate
analysis. All patients with BM relapse, except 2 who were lost to
follow-up within 1 year of relapse, died. The patient with isolated
testicular relapse underwent localized radiotherapy and chemotherapy
and has survived for 89 months post-HSCT at last follow-up.
Another 15 patients died during the initial year post-transplantation
due to causes other than relapse for a 1-year cumulative TRM incidence
of 26.4±6.1%. Although univariate study of prognostic factors
for TRM revealed donor type (P=0.002) and HLA compatibility
(P=0.022) to be significant variables, none proved to maintain
significance on multivariate study. Causes of TRM were as follows:
pneumonia and acute respiratory distress syndrome 5, acute GvHD
3, thrombotic microangiopathy 2, pulmonary hemorrhage 2, veno-
occlusive disease 1, sepsis 1, and acute renal failure 1. Nearly all non-
relapse deaths occurred during the first year post-transplantation,
with only 1 patient dying of chronic GvHD beyond this period.
5. Analysis of overall survival
The estimated 5-year OS for the entire cohort was 48.3±7%, showing
a rate similar to the DFS. Reanalysis according to donor type with
consideration of HLA compatibility resulted in the following OS
rates: 75±8.9% for MSD, 38.5±13.5% for MUD, and 14.3±9.4% for
MMUD. Significant differences were noted when comparing the OS
for MSD to that for either MUD (P=0.018) or MMUD (P<0.001).
Discussion
In this study, we report the outcomes of allogeneic HSCT undertaken
in children with ALL in second CR at a single institution during a
lengthy period spanning more than 17 years. As far as we know, this
is the first such report to derive from a Korean pediatric population.
The overall 45.3±6.9% incidence of grade II to IV acute GvHD
was considerably higher than reported rates in similar studies6,7). The
lack of routine in vivo T cell depletion with the use of ATG in the
conditioning regimen for unrelated HSCTs done in the early period
of the study may have had a role in increasing acute GvHD incidence.
Cumulative incidence of 28.5±6.3% for chronic GvHD was similar
to the 22 to 27% reported from large cohort studies comprising both
matched sibling and alternative donor HSCTs13,14).
Overall, less than half the patients of the cohort survived disease-free.
Also of note, the DFS and OS were similar emphasizing once more
the extremely poor prognosis once a patient relapsed after HSCT.
Excluding patients lost to follow-up, only 1 patient with isolated
testicular relapse survived after relapse. In comparison, the DFS
of 45.2% for the overall cohort is similar to previous reports based
on HSCTs from heterogenous donor types7,15), but is considerably
lower than the 67.1% 3-year DFS reported by one study6) which also
included patients transplanted in first CR. Sub-analysis according to
donor type lends some evidence for this discrepancy; although the
estimated DFS of 68% for MSD HSCT was superior or comparable
to previous results, the 38.5% DFS for MUD HSCT was much
lower6,7). Hence, unlike these reports which conclude on similar results for
MSD and alternative donor HSCT, there was at least a trend towards
a significant difference when comparing MSD and MUD HSCT
(P=0.051).
Akin to the survival analyses, the regression modeling revealed that
donor type, sibling versus unrelated donor, was the only significant
prognostic factor for DFS. As all sibling donors were fully HLA-
matched except for 1 donor who showed 1 allele mismatch with a
sibling patient, how much of the prognostic significance of a sibling
donor pertains to HLA compatibility, and how much is based on the
potential benefits of a sibling donor beyond standard HLA typing
would require further comparative study of a cohort consisting of
MSD and high resolution-typed MUD HSCTs only. Our study
also revealed the lack of a survival benefit for patients who underwent
HSCT after a lengthy period of first remission compared to those
who relapsed early on during treatment. This is an important finding
considering that nearly half the patients (45%) in our cohort relapsed
after at least 3 years of CR status. Previous studies indicate either a
survival advantage for late relapse patients7), or are inconclusive as to
whether HSCT improves upon the approximately 50% survival rate
based on chemotherapy only16), and our results underscore the impor-
tant question of whether patients with late relapse may benefit from
HSCT.
P=0.014
MSD=68±9.3%
MUD=38.5±13.5%
MMUD=14.3±9.4%
Time (mo)
Survival
0 12 24 36 48 60
1.0


0.8

0.6


0.4


0.2

Fig. 1. Estimated 5-year disease-free survival curves by donor type
considering human leukocyte antigen compatibility. MSD, matched
sibling donor; MUD, matched unrelated donor (high or low resolution);
MMUD, mismatched unrelated donor (high or low resolution).