To the Editor:

We have evaluated the occurrence of the AML1/ETO fusion transcripts by reverse transcription-polymerase chain reaction (RT-PCR) analysis1 in 7 patients with t(8; 21)(q22; q22) acute myeloid leukemia (AML) who underwent allogeneic bone marrow transplantation (BMT; n = 6) or peripheral blood progenitor cell transplantation (PBPCT; n = 1). We found here that the AML1/ETO fusion transcripts were detectable in only 2 of 7 patients in the long-term follow-up posttransplant (12 and 112 months post-BMT). One of these two patients who were tested positive for the AML1/ETO fusion transcript at 1 month and at 12 months posttransplant remained also to be mixed chimeric by variable number of tandem repeats PCR (VNTR-PCR) analysis at 12 months post-BMT, but relapsed 5 months later and subsequently died. However, another patient who was AML1/ETO positive up to 112 months posttransplant remained in complete remission during the whole observation period. This patient had a complete chimerism status by VNTR-PCR at 3 months and at 48 months post-BMT.

Three of five patients who were initially AML1/ETO positive in the RT-PCR assay converted 6, 9, and 30 months posttransplant, respectively, and showed at least two consecutive negative PCR assays for the AML1/ETO fusion transcript. All patients who achieved a molecular remission by the AML1/ETO PCR assay remained in stable cytogentic remission.

Studies about the presence of the AML1/ETO fusion transcripts after allogeneic BMT or PBPCT are rare and results are discussed controversely.1-5 Recently, Jurlander et al2 reported that AML1/ETO fusion transcripts in patients treated with allogeneic BMT for t(8; 21) leukemia were still persistent post-BMT in all 9 of 9 evaluable patients.1 According to these investigators, persistence of the leukemic clone after BMT suggests that allogeneic BMT, like conventional chemotherapy and autologous BMT, is usually not sufficient to eliminate expression of AML1/ETO transcripts.2 Contrary to Jurlander et al,2 we showed here, using a similar sensitive method, that allogeneic transplantation leads to sustained suppression or elimination of the leukemic clone in most of the studied patients due to a combination of pretransplantation marrow-ablative conditioning regimen and allogeneic immune reaction (graft-versus-leukemia effect). Our results are supported by a study of Miyamoto et al,3 who reported that the AML1/ETO fusion transcript could not be detected in 4 patients who had been in maintaining remission for more than 30 months after allogeneic BMT. In three other studies,4-6 a total of 5 patients were analyzed by RT-PCR for the AML1/ETO fusion transcripts post-BMT. In 3 of 5 patients the AML1/ETO fusion transcript was consistently detected in the long-term follow-up, whereas 2 patients achieved a molecular remission in these studies.

These data may suggest that patients who achieved a molecular remission after allogeneic transplantation might have a better prognosis with respect to leukemic relapse than their counterparts with a persisting positive AML1/ETO PCR test. However, the detection of the AML1/ETO fusion transcript seems to have not that high of a risk of leukemic relapse after allogeneic BMT as, for example, the detection of BCR/ABL transcripts.

In absence of quantitative PCR assays, chimerism analysis using sensitive VNTR-PCR techniques might help to increase the possible predictive value of a positive AML1/ETO PCR assay in regards to leukemic relapse posttransplant. By having a lower sensitivity usually by a factor of 101 to 102, chimerism analysis by VNTR-PCR may detect a larger number of cells of host-type hematopoiesis. For example, it has thus been shown that, in patients with chronic myeloid leukemia after BMT, a mixed chimerism is associated with a higher incidence of MRD and risk of leukemic relapse.7 8 

To our knowledge there are now reports on a total of 23 patients who have been studied for expression of the AML1/ETO transcript after allogeneic BMT.1-1-1-7 Of these patients, 15 have been found to have persistent expression, 7 were or became negative, and 1 was not evaluable. The discrepancy most likely reflects the lack of consensus on when to score a given sample as negative. Our data suggested that the sensitivity of each assay, the amount of starting material, or the source of the material (ie, BM v blood) might all contribute to some of the negative results obtained.1-7 For a patient to be considered negative at a given timepoint in our study, samples had to (1) be amplified in three independent experiments using 2.0 μg of total cellular RNA per reaction, (2) be succesfully amplified for the β-actin in each reaction; (3) be performed simultaneously with an RT-PCR showing a sensitivity for detection of the AML1/ETO transcript of ≥1 × 105 in all three reactions, and (4) assays had to be performed on blood and BM. Taken together, these data suggest that, in the majority of patients, persistent expression of the AML1/ETO is compatible with continued clinical remission and, with the reported follow-up times of up to 10 years, even cure. Recently, similar results, although not after allogeneic BMT, were reported in childhood ALL.1-8 

REFERENCES

1-1
Miyamoto
T
Nagafuji
K
Akashi
K
Harada
M
Kyo
T
Akashi
T
Takenaka
K
Mizuno
G
Gondo
H
Okamura
T
Dohy
H
Niho
Y
Persistence of multipotent progenitors expressing AML1/ETO transcripts in long-term remission patients with t(8; 21) acute myelogenous leukemia.
Blood
87
1996
1789
1-2
Kusec
R
Laczika
K
Knöbl
P
Friedl
J
Greinix
H
Kahls
P
Linkesch
W
Schwarzinger
I
Mitterbauer
G
Purtscher
B
Haas
OA
Lechner
K
Jaeger
U
AML1/ETO fusion mRNA can be detected in remission blood samples of all patients with t(8; 21) acute myeloid leukemia after chemotherapy or autologous bone marrow transplantation.
Leukemia
8
1994
735
1-3
Satake
N
Maseki
N
Kozu
T
Sakashita
A
Kobayashi
H
Sakurai
M
Ohki
M
Kaneko
Y
Disappearance of AML1/MTG8(ETO) fusion transcripts in acute myeloid leukemia patients with t(8; 21) in long-term remission.
Br J Haematol
91
1995
892
1-4
Saunders
MJ
Tobal
K
Liu
Yin JA
Detection of t(8; 21) by reverse transcriptase polymerase chain reaction in patients in remission of acute myeloid leukaemia type M2 after chemotherapy or bone marrow transplantation.
Leuk Res
18
1994
891
1-5
Tobal
K
Liu
Yin JA
Monitoring of minimal residual disease by quantitative reverse transcriptase-polymerase chain reaction for AML1-MTG8 transcripts in AML-M2 with t(8; 21).
Blood
88
1996
3704
1-6
Elmaagacli
AH
Beelen
DW
Stockova
J
Trzensky
S
Kroll
M
Stein
C
Opalka
B
Schaefer
UW
Detection of AML1/ETO fusion transcripts in patients with t(8; 21) acute myeloid leukemia after allogeneic bone marrow transplantation or peripheral blood progenitor cell transplantation.
Blood
90
1997
3230
1-7
Jurlander
J
Caligiuri
MA
Ruutu
T
Baer
MR
Strout
MP
Oberkircher
AR
Hoffmann
L
Ball
ED
Frei-Lahr
DA
Christiansen
NP
Block
AMW
Knuutila
S
Herzig
GP
Bloomfield
CD
Persistence of the AML1/ETO fusion transcript in patients treated with allogeneic bone marrow transplantation for t(8; 21) leukemia.
Blood
88
1996
2183
1-8
Roberts
WM
Estrov
Z
Ouspenskaia
MV
Johnston
DA
McClain
KL
Zipf
TE
Measurement of residual leukemia during remission in childhood acute lymphoblastic leukemia.
N Engl J Med
336
1997
317
1
Downing
JR
Head
DR
Curcio-Brint
AM
Hulshof
MG
Motroni
TA
Raimondi
SC
Carroll
AJ
Drabkin
HA
Willman
C
Theil
KS
Civin
CI
Erickson
P
An AML1/ETO fusion transcript is consistently detected by RNA-based polymerase chain reaction in acute myelogenous leukemia containing the (8; 21)(q22; q22) translocation.
Blood
81
1993
2860
2
Jurlander
J
Caligiuri
MA
Ruutu
T
Baer
MR
Strout
MP
Oberkircher
AR
Hoffmann
L
Ball
ED
Frei-Lahr
DA
Christiansen
NP
Block
AMW
Knuutila
S
Herzig
GP
Bloomfield
CD
Persistence of the AML1/ETO fusion transcript in patients treated with allogeneic bone marrow transplantation for t(8; 21) leukemia.
Blood
88
1996
2183
3
Miyamoto
T
Nagafuji
K
Akashi
K
Harada
M
Kyo
T
Akashi
T
Takenaka
K
Mizuno
S
Gondo
H
Okamura
T
Dohy
H
Niho
Y
Persistence of multipotent progenitors expressing AML1/ETO transcripts in long-term remission patients with t(8; 21) acute myelogenous leukemia.
Blood
87
1996
4789
4
Kusec R, Laczika K, Knobl P, Friedl J, Greinix H, Kahls P, Linkesch W, Schwarzinger I, Mitterbauer G, Purtscher B, Haas OA, Lechner K, Jaeger U: AML1/ETO fusion mRNA can be detected in remission blood samples of all patients with t(8; 21) acute myeloid leukemia after chemotherapy or autologous bone marrow transplantation. Leukemia. 8(5):735, 1994
5
Satake
N
Maseki
N
Kozu
T
Sakashita
A
Kobayashi
H
Sakurai
M
Ohki
M
Kaneko
Y
Disappearance of AML1-MTG8(ETO) fusion transcript in acute myeloid leukaemia patients with t(8; 21) in long-term remission.
Br J Haematol
91
1995
892
6
Saunders
MJ
Tobal
K
Yin
JA
Detection of t(8; 21) by reverse transcriptase polymerase chain reaction in patients in remission of acute myeloid leukaemia type M2 after chemotherapy or bone marrow transplantation.
Leuk Res
18
1994
891
7
Elmaagacli
AH
Becks
HW
Beelen
DW
Stockova
J
Bützler
R
Opalka
B
Schaefer
UW
Detection of minimal residual disease and persistence of host-type hematopoiesis: A study in 28 patients after sex-mismatched, non T-cell-depleted allogeneic bone marrow transplantation for Philadelphia-chromosome positive chronic myelogenous leukemia.
Bone Marrow Transplant
16
1995
823
8
Mackinnon
S
Barnett
L
Heller
G
O'Reilly
RJ
Minimal residual disease is more common in patients who have mixed T-cell chimerism after bone marrow transplantation for chronic myelogenous leukemia.
Blood
83
1994
3409
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