Bone marrow versus peripheral blood sibling transplants in acquired aplastic anemia

30 Pages·2012·1.24 MB·English

by  Ferrata Storti

Published Ahead of Print on February 7, 2012, as doi:10.3324/haematol.2011.054841.
Copyright 2012 Ferrata Storti Foundation.
Early Release Paper
Bone marrow versus peripheral blood sibling transplants in acquired
aplastic anemia: survival advantage for marrow in all age groups
by Andrea Bacigalupo, Gerard Socie', Hubert Schrezenmeier, Andre' Tichelli,
Anna Locasciulli, Monika Fuhrer, Antonio Risitano, Carlo Dufour, Jakob Passweg,
Rosi Oneto, Mahmoud Aljurf, Catherine Flynn, Valerie Mialou, Rose Marie Hamladji,
and Judith Marsh
Haematologica 2012 [Epub ahead of print]
Citation: Bacigalupo A, Socie' G, Schrezenmeier H, Tichelli A, Locasciulli A, Fuhrer M,
Risitano A, Dufour C, Passweg J, Oneto R, Aljurf M, Flynn C, Mialou V, Hamladji RM,
and Marsh J. Bone marrow versus peripheral blood sibling transplants in acquired aplastic
anemia: survival advantage for marrow in all age groups. Haematologica. 2012; 97:xxx
doi:10.3324/haematol.2011.054841
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DOI: 10.3324/haematol.2011.054841
Bone marrow versus peripheral blood sibling transplantsin acquired
aplastic anemia: survival advantage for marrow in all age groups

Running title: marrow vs blood transplants in aplastic anemia

Andrea Bacigalupo, Gérard Socié, Hubert Schrezenmeier, Andre Tichelli, Anna Locasciulli,
Monika Fuehrer, Antonio M. Risitano, Carlo Dufour, Jakob R. Passweg, Rosi Oneto,
Mahmoud Aljurf, Catherine Flynn, Valerie Mialou, Rose Marie Hamladji,
and Judith C. W. Marsh for the Aplastic Anemia Working Party of the European Group
for Blood and Marrow Transplantation (WPSAA-EBMT)

Corresponcence
Andrea Bacigalupo, Divisione Ematologia e Trapianti di Midollo Osseo
Ospedale San Martino, Genova, Italy. Phone: international +39.010.355469.
Fax: international +39.010355583. E-mail: [email protected]

Key words: aplastic anemia, allogeneic transplantation, bone marrow transplants,
peripheral blood transplants.

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ABSTRACT

Background. Bone marrow has been shown to be superior to peripheral blood, as a
stem cell source, in young patients (<20 years of age) with acquired aplastic anemia
undergoing a matched sibling transplant. The aim of this study was to test whether this
was currently true also for older acquired aplastic anemia patients.

Design and Methods. We have therefore analyzed 1886 patients, who received a first
matched sibling transplant between 1999 and 2009 : patients were selected as having
acquired aplastic anemia, a first transplant from an human leukocyte antigen identical
sibling, and bone marrow(n=1163) or peripheral blood (PB) (n=723) as a stem cell source.

Results. In multivariate COX analysis negative predictors for survival were the following:
patient age >20 years (RR 2.0, p<0.0001), an interval diagnosis-transplant (Dx-Tx) >114
days (RR 1.3, p=0.006) , no anti-thymocyte globulin in the conditioning (RR 1.6,
p=0.0001), a conditioning regimen other than cyclophosphamide (RR=1.3, p=0.008) and
the use of peripheral blood as a stem cell source (RR 1.6, p<0.00001). The survival
advantage for bone marrow compared to peripheral blood, was significant in patients aged
1-19 years (90% vs 76% p<0.00001) as well as in patients aged >20 years (74% vs 64%,
p=0.001). The advantage for bone marrow over peripheral blood was maintained above
the age of 50 years (69% vs 39% p=0.01). Acute and chronic graft vs host disease were
more frequent in peripheral blood transplants. Major causes of death were GvHD (2% vs
6% in bone marrow/peripheral blood respectively), infections (6% vs 13%), and rejection
(1,5% vs 2,5%).

Conclusions. This study shows that bone marrow should be the preferred stem cell
source for matched sibling transplants in acquired aplastic anemia, in all age groups.
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INTRODUCTION

Graft versus host disease (GvHD) and graft rejection have been major issues for
successful allogeneic bone marrow transplantation (BMT) in patients with acquired severe
aplastic anemia (SAA) (1) . With the advent of peripheral blood (PB) as a stem cell
source, it was thought that rejection would be reduced : however a first EBMT/CIBMTR
comparison between marrow (BM) and PB in 2007 , failed to confirm this hypothesis, and
showed a significant survival advantage for BM over PB transplants (2). In that study ,
including 692 patients, the survival advantage for BM was statistically significant under the
age of 20, but not for older patients , although the survival advantage was similar, possibly
due to smaller patient numbers.
A second study by the CIBMTR , has recently compared different stem cell sources :
granulocyte-colony stimulating factor (G-CSF)-stimulated bone marrow (G-BM) (n = 78),
unstimulated bone marrow (BM) (n= 547), or peripheral blood progenitor cells (PB) (n =
134) in sibling grafts between 1997 to 2003 (3) . Grade II-IV and III-IV acute GvHD, and
cGVHD were significantly higher after PB transplants compared to BM. Mortality was lower
after transplantation of BM compared to G-BM and PB. This study concludes that BM is
the preferred stem cell source for HLA-matched sibling transplants for SAA (3).
Despite these results, PB is still being used as a stem cell source in patients with
acquired aplastic anemia : a recent survey of the Aplastic Anemia Working Party of the
European Group for Blood and Marrow Transplantation (WPSAA-EBMT) has shown that
40% of transplants were from PB in 2009 (unpublished). This is difficult to understand ,
particularly because of the significant greater risk of graft versus host disease, both acute
and chronic in PB grafts (4) , which may have short and long term consequences on
morbidity and mortality, without the potential added value of graft versus leukemia effect
(5). The justification for the use of PB, despite higher risk of GvHD, is the propensity of
SAA patients to reject the graft, and it is thought that PB may reduce this risk. However,
there is little evidence that this is the case: indeed in the 2007 study (2), the risk of
primary graft failure (9% vs 9%) and secondary graft failure (6% vs 7%), was identical in
patients receiving BM or PB grafts. Based on data available in the literature, it would
currently seem that PB grafts expose SAA patients to a higher mortality due to more
GvHD, without the benefit of a reduced risk of rejection .
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To assess whether more recent findings would confirm or disprove these data, we
have now analyzed 1886 SAA patients transplanted between 1999 and 2009 , and are
now reporting the results of this study.

DESIGN AND METHODS

Patients
Patients were treated in 303 EBMT Centers (see Appendix), and entered in the WPSAA-
EBMT Registry as per standard procedures. Patients were selected as having acquired
aplastic anemia , a first transplant from an HLA identical sibling, between 1999-2009, and
marrow (BM) or peripheral blood (PB) as a stem cell source. PB stem cells were collected
from sibling donors , after mobilization with G-CSF according to standard procedures.. BM
was Combined BM/PB or BM/CB transplants were excluded , together with constitutional
marrow failure and donors other than HLA identical siblings.
Graft vs host disease prophylaxis, was heterogeneous: however, the major aggregations
were cyclosporin alone (CsA), CsA+ other agents, CsA+ methotrexate (MTX), CsA+MTX
plus other agent. Because CsA+MTX was the predominant regimen, and because in
univariate analysis it proved to offer a survival advantage, patients were ultimately divided
in CsA+MTX vs all other regimens.
Conditioning regimens also were heterogeneous: cyclophosphamide 200 mg/kg was the
regimen used in the large majority of patients; radiation was used in 114 patients as total
lymphoid irradiation (TLI) , in 31 as total body irradiation (TBI), and in 7 as thoraco
abdominal irradiation (TAI) .
Severity of the aplasia was recorded in 487 patients as very severe (n=192), severe
(n=114) and non severe(n=181).
Table 1 outlines clinical characteristics of patients. The proportion of patients receiving
PB grafts in the 10 year period was as follows : 36,2% in 1999-2001, 36,8% in 2002-2003,
39,3% in 2004-2005, 40,5% in 2006-2007 and 38,8% in 2008-2009.
There were significant differences between BM and PB grafts (Table 1) : the latter were
older, were grafted more recently, had more frequently CMV+ donors, were grafted after a
longer interval from diagnosis, received more frequently conditioning regimen other than
cyclophosphamide 200 mg/kg (CY200) , including regimens with radiation, had more
frequently a GvHD prophylaxis other than cyclosporine methotrexate (CsA+MTX), and
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were less likely to receive anti-thymocyte globulin (ATG) in the conditioniong regimen ;
they also had a shorter follow up (Table 1) .
Acute graft versus host disease (aGvHD) and chronic graft versus host disease (cGvHD)
were diagnosed according to standard criteria and recorded.

Statistical analysis
Patient data were analyzed with the NCSS package. Comparisons were carried out using
the chi-square test for categorical variables and the non-parametric Mann-Whitney test for
continuous variables. The end point for survival analysis was death due to any cause.
Univariate and multivariate survival analyses were carried out using the Cox proportional
hazard model.

RESULTS

Engraftment
The proportion of patients recorded as non-engrafted in BM vs PB was respectively 5,5%
and 7.2% (p=0.1); the proportion of engrafted 90.7% and 89.9% (p=0.5), and patients who
lost their graft were 1,3% and 1.4% (p=0.2).
The median day for neutrophil engraftment was day 20 for BM patients (3-156) and day 15
for PB patients (5-68) (p<0.0001). The median day for platelet engraftment was day 27 (4-
305) for BM, and day 15 for PB patients (5-68) (p<0.0001).

Graft versus host disease (GvHD)
Acute GvHD grade II-IV , developed in 11% vs 17% of patients receiving BM or PB grafts
(p=0.001) and grade III-IV developed in 4% vs 7% respectively (p=0.005). Chronic GvHD
developed in 11% vs 22% BM vs PB grafts (p<0.00001) and extensive cGvHD in 4% vs
8% respectively (p=0.0004) (Figure 1).
The use of ATG reduced the risk of acute GvHD II-IV from 16% to 8% (p=0.0001) and of
chronic GvHD from 17% to 12% (p=0.001).

Univariate analysis
In univariate analysis there were 6 negative predictors of survival in the whole cohort of
patients : age > 20 years, an interval diagnosis transplant (DxTx) over 114 days (median),
a preparative regimen without anti-thymocyte globulin (ATG) , a conditioning regimen other
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than cyclophosphamide 200 mg/kg (CY200), stem cell source, GvHD prophylaxis other
than CsA+MTX and the use of radiation in the conditioning regimen (Table 2). Donor age
and gender, recipient gender, including female donors in male recipient, previous
immunosuppressive therapy, CMV status and year of transplant, were not significant.
The overall actuarial 10 year survival for the entire population was 74%; it was 84% vs
72% (p<0.0001) for an interval diagnosis transplant (Dx-Tx) of </>144 days (Figure 2a);
87% vs 70% (p<0.00001) for patients aged 1-20 or over 20 years (Figure 2b); 80% vs 72%
(p=0.0004) for patients prepared with cyclophosphamide 200 mg/kg (CY200) or other
regimens (Figure 2c); 84% vs 74% (p=0.0001) for patients receiving or not anti-thymocyte
globulin (ATG) in the conditioning regimen (Fig.2d), 81% vs 75% (p=0.004) for patients
given CsA+MTX vs other prophylaxis, and 61% vs 78% for patient receiving or not
radiation (p<0.001).

Age and stem cell source
In univariate analysis the actuarial survival of patients receiving BM or PB was 84% vs
68% (p<0.00001): when stratified by age (<=/> 20 years) and stem cell source survival is
depicted in Figure 3: under the age of 20 the survival advantage of BM over PB was 90%
vs 76% (p<0.00001) and in patients aged >20 years it was 74% vs 64% (p=0.001). In
patients over the age of 50 the advantage of BM (n=58) over PB (n=76) was 69% vs 39%
(p=0.01).

Survival: multivariate analysis
Variables significant in univariate analysis were entered in a multivariate model, and 5
proved independent negative predictors (Table 2): older age, longer interval diagnosis
transplant, no ATG in the conditioning regimen , a regimen other than CY200 and PB as a
stem cell source.

Survival: identification of different risk groups
We then wanted to assess the effect of stem cell source in patients with different risk of
mortality: for this purpose the 4 negative predictors, interval diagnosis –transplant, age,
ATG and conditioning regimen, were used to identify 3 groups of patients, with
significantly different outcomes (Figure 4a): low risk (0-1 negative predictor; n=631;
actuarial survival 89%), medium risk (2 negative predictors; n=654; survival 78%) and high
risk (3-4 negative predictors ; n=601; survival 64%) (Figure 4a). The actuarial survival of
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BM vs PB grafts in low risk patients (Figure 4b), was 92% vs 80% (p=0.0001), in
intermediate risk patients it was 84% vs 74% (p=0.02) (Figure 4c) and 72% vs 59%
(p=0.006) in high risk patients (Figure 4d).

Causes of death
Table 3 outlines causes of death in patients receiving BM or PB grafts: there were more
deaths due to GvHD in the PB group (2% vs 6%, p=0.00001) and infections (6% vs 13%,
p<0.00001). Deaths related to rejection were comparable , with a trend for a greater risk in
PB graft recipients (1,5% vs 2,5% respectively, p=0.07) (Table 3).

Centers and stem cell source
There were 305 Centers contributing data for this study (see Appendix): 116 Centers used
PB as a stem cell source in 0% of the transplants, 38 in 1-25% of their transplants , 53
Centers used PB in 26-50% and 98 Centers in >50% of their grafts. The average crude
survival in Centers never using PB was 84%, for Centers using 1-25% of PB grafts, it was
80%, for Centers using 26-50% of PB it was 78%, for Centers using >50% PB grafts it was
72%. We then looked at patients contributed by each Center and use of PB grafts: of the
large Centers contributing >20 patients each, only 1 never used PB, and 30% of Centers
used more than 50% of PB grafts irrespective of their size. Sixtytwo Centers never used
BM and 116 never used PB.

DISCUSSION

We have shown in this large EBMT registry based study , that patients with
acquired aplastic anemia, grafted from HLA identical siblings, have a survival advantage in
all age groups , when given bone marrow as compared to peripheral blood transplants,
suggesting BM should be the preferred stem cell source . We have also shown , or
confirmed , that other predictors of survival are patients age, the use of ATG in the
conditioning, the interval from diagnosis to transplant and the use of a conventional
cyclophosphamide 200 mg/kg conditioning regimen.
In the previous joint EBMT/CIBMTR study on stem cell source (2) , the survival
advantage for BM over PB was 12% in patients under 20 years of age, and 12% in
patients over 20 years, but statistically significant only in the young patients. In the present
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analysis the difference is similar, 14% in young patients and 10% in older patients, but
highly significant in both groups due to the large number of patients .
There were differences in patients characteristics when BM recipient were compared with
PB recipients, and this would argue for a selection of more difficult patients in the PB
group: indeed PB grafts were older, were grafted later after diagnosis, and had received
more frequently a conditioning regimen other than cyclophosphamide 200 mg/kg ,
including the use of radiation; on the other hand they were grafted more recently . To
answer this important question, these variable were tested in univariate and multivariate
analysis : unfavourable predictors of outcome were found to be older age, no ATG in the
conditioning, a longer interval diagnosis-transplant, beyond 114 days, which was the
median interval, and a conditioning regimen other than cyclophosphamide 200 mg/kg.
We then assigned a score of 1 for each unfavourable factor, and 3 risk groups could be
identified, with 0-1, 2 and 3-4 risk factors, with significantly different actuarial survival
(89%,78%,64%). Having identified the patients who would be expected to do worse, we
then looked at the use of BM and PB in these different risk groups: the survival advantage
for BM was evident in all 3 groups, thus not supporting the hypothesis that PB grafts
produce better result in difficult patients. We also looked at the very old patients (>50
years of age), and also here BM grafts did significantly better than PB grafts. These
results were confirmed in a multivariate COX model, in which stem cells source was
included as a variable: in this model, after correcting for known negative predictors, the
relative risk of death of PB transplants was 1.6 (p<0.00001). The recent CIBMTR study
(3) confirms these results. When looking at a Center effect , we could subdivide Centers
in 4 groups: using PB as the stem cell source never (0%), in 1-25%, 26-50% and 51-100%
of their grafts: worst survival was seen in the latter group, using a high proportion of PB
grafts, best in the first group. However, we could not show that large Centers were using
more BM, since only 1 in 10 reporting over 20 patients never used PB. Therefore a large
number of small Centers , contributing 1 or 2 patients each, used BM only . In our opinion
this makes the result still more striking.
But why should PB transplants do worse than BM transplants? We found more
deaths due to GvHD, and infections, which are often combined causes of failure.
Interestingly , despite faster neutrophil and platelet engraftment, we could find no
difference in the proportion of patients recorded as engrafted, in the proportion of patients
who lost their graft , nor a reduction of death classified as due to rejection (1.5% for BM
and 2.5% for PB), in keeping with the previous EBMT/CIBMTR study (2). Thus PB grafts
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fail to reduce the incidence and mortality due to graft failure, but increase the risk of GvHD,
thus exposing the patient to increased morbidity and mortality. In particular we found twice
as much chronic GvHD in PB grafts (22% vs 11%), without the need for a graft versus
leukemia effect. This being the case, it is likely that unrelated PB transplants will also yield
similar inferior results when compared to BM transplants for aplastic anemia: a preliminary
analysis of 451 BM and 153 PB rafts , suggests a 20% survival advantage for BM (68% vs
48%) in the period 1999-2009 (EBMT WPSAA Registry 2011, unpublished). In keeping
with these results, the CIBMTR has recently published a paper showing that BM offers a
survival advantage over PB as a stem cell source, in aplastic anemia undergoing an
unrelated donor transplant (5).
Therefore, there is currently no good reason to collect PB cell for transplants in aplastic
anemia, neither donor safety , exposed to a significant greater risk of severe adverse
events , when donating PB (6), nor advantage for recipients: it is therefore hoped that for
this particular indication, the current propensity of the Centers to collect PB , both related
and unrelated, may be overcome by the evidence provided in the current ,as well as in
other reports.
In addition to stem cell sources, transplant strategies are also relevant for optimal
outcome: in this study the use of ATG in the conditioning regimen was associated with
statistically improved survival in univariate and multivariate analysis, possibly because we
know that ATG reduces acute and chronic GvHD and improves engraftment (8-11). It
should be noted that a prospective randomized trial had failed to show an advantage for
the use of ATG in the conditioning regimen (12): the advantage for ATG in survival was
6% in that trial, whereas in our study it is 10%, but with a larger number of patients, and
therefore highly significant. Thus, the conventional cyclophosphamide 200 mg/kg and
ATG, remains the standard of care , as advocated many years ago by the Seattle group
(1) , and confirmed with long term follow up (13,14): this is true also for transplants in
developing countries (15). An alternative to ATG is Alemtuzumab, as shown in a recent
retrospective multicentre study (16), in which Alemtuzumab combined with fludarabine
and low dose cyclophosphamide, produced a low incidence of chronic GVHD and very
encouraging survival : also in that study there was worse overall survival in patients who
received PBSC compared to BM grafts.
The hypothesis that conditioning regimens, including fludarabine (17), will overcome the
negative effect of age (18), should be tested prospectively before one can advocate their
use as a standard of care: indeed recent encouraging results have been published by the
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