1. Introduction
Cytogenetic studies of acute myeloid leukemia (AML)
have contributed substantially to our understanding of the
remarkable histopathologic, immunophenotypic, and clinical
heterogeneity of AML. Multiple recurring chromosomal
aberrations have been identified, and in many instances,
genes altered by these aberrations have been mapped and
cloned [1,2]. Further characterization of the genes rearranged
by AML-associated translocations and inversions has
pro-vided insights into the mechanisms of leukemogenesis and
will likely facilitate designing of novel therapeutic strategies
that target particular genetic abnormalities in leukemic blasts
[3,4]. In addition, acquired cytogenetic abnormalities,
whether characterized at the molecular level or not, have
been shown to represent tumor markers of diagnostic and
prognostic importance [5,6]. Many recurrent aberrations
have been correlated with presenting hematologic and
mor-phologic parameters. Selected chromosomal aberrations, and
their molecular equivalents, are now being used to help
define distinct disease categories within AML in the new
World Health Organization classification of hematologic
malignancies [7]. Moreover, karyotypic findings at diagnosis
have been repeatedly shown to be among the most significant
independent prognostic factors regarding AML [8-19].
In this article, we present major cytogenetic findings
regarding AML and review their prognostic implications for
adult patients with AML.
2. Overview of Cytogenetic Findings in AML
Cytogenetic analysis is usually performed on a bone
mar-row or blood sample (preferably the former) that is obtained
from an AML patient at diagnosis and contains leukemic
blasts. The bone marrow sample is subjected to unstimulated
24- or 48-hour culture in vitro. Meaningful cytogenetic results
are attained in the vast majority of adults with AML. Most
large cytogenetic studies, involving more than 100 patients,
have reported failure rates below 10% (range, 2% to 27%)
[8,11-13,15,16,18-24]. Among successfully analyzed adults with
AML, at least 1 clonal chromosomal aberration, ie, an identical
structural rearrangement or an extra copy of the same
chro-mosome present in at least 2 mitotic cells or the same
chromo-some missing from 3 metaphases, has been detected in 54% to
78% of patients [8,11-15,19,21-23,25-27], although both higher
[24] and lower [16,28] percentages have also been reported.
The rates of aberration detection in many [15,21,27,29]
but not all [16,30] of more recent series have been higher
Prognostic Value of Cytogenetic Findings in Adults
With Acute Myeloid Leukemia
Krzysztof Mrózek,* Kristiina Heinonen, Clara D. Bloomfield
Division of Hematology and Oncology and the Comprehensive Cancer Center, The Ohio State University,
Columbus, Ohio, United States of America
Received June 19, 2000; accepted June 23, 2000*Correspondence and reprint requests: Krzysztof Mrózek, MD, PhD, Division of Hematology and Oncology and the Comprehensive Cancer Center, The Arthur G. James Cancer Hospital and Richard J. Solove Research Institute, Rm. 1248B, The Ohio State University, 300 West Tenth Ave., Columbus, OH 43210-1228, USA; 614-293-3150; fax: 614-293-3575 (e-mail: mrozek-1@medctr.osu.edu).
Abstract
The majority of adults diagnosed with acute myeloid leukemia (AML) display acquired cytogenetic aberrations at
presen-tation. Numerous recurring chromosomal abnormalities have been and continue to be identified in AML. In many instances,
genes altered by these aberrations have been cloned, providing insights into the mechanisms of leukemogenesis and paving
the way to designing novel therapeutic strategies that target specific genetic abnormalities in leukemic blasts. Moreover,
karyotypic abnormalities, whether molecularly characterized or not, are among the most important independent prognostic
factors in AML and are being used in the clinical management of AML patients. In this review, we present an overview of
major cytogenetic findings in AML and discuss associations between karyotype and clinical outcome of adults with AML.
Int
J Hematol.
2000;72:261-271.
©2000 The Japanese Society of Hematology
Key words:
Acute myeloid leukemia; chromosomal aberrations; karyotyping; prognosis
HEMATOLOGY
261
Hematology
than those in the earliest studies [5]. This difference is likely
because of improvements in cytogenetic methodology and
because of the increased level of experience in detection of
subtle structural aberrations, eg, inv(16)(p13q22), t(11;19)
(q23;p13.1), or t(15;17)(q22;q12-21). Nonetheless, a
substan-tial proportion of AML patients has an exclusively normal
karyotype. The incidence of chromosomal abnormalities in
AML may still be underestimated, as suggested by reports
on karyotypically normal patients who are positive for gene
fusion created by one of the recurrent chromosomal
aberra-tions, eg,
PML-RAR
a
produced by t(15;17) or
CBF
b
-MYH11
by inv(16) [31-34]. Indeed, in rare cases, the presence
of a chromosomal aberration may have escaped detection by
the cytogenetic laboratory. In other patients, however, the
gene fusion results from a cryptic rearrangement involving
segments smaller than the length of a single band that is thus
unrecognizable by standard cytogenetic analysis. Examples of
cryptic insertions of a very small segment from 17q
contain-ing the
RAR
a
gene into the locus of the
PML
gene on
chro-mosome 15q have been published [35]. On the other hand,
the number of patients truly positive for gene fusion
tran-scripts in the absence of cytogenetically detectable
aberra-tions may be lower than indicated by some studies using
reverse transcription–polymerase chain reaction (RT-PCR)
to detect rearrangements, because of the known propensity
of RT-PCR to generate false-positive results [36,37]. At any
rate, karyotypically normal AML patients positive for the
specific gene fusion are rare and constitute only a fraction of
all AML cases with a normal karyotype [23,31].
The notion that lack of microscopically discernible
aber-rations in a sizeable number of AML patients is an authentic
phenomenon, not a failure in their detection, is supported by
results of spectral karyotyping (SKY). SKY is a fluorescence
in situ hybridization (FISH)-based technique allowing for
simultaneous display of all human chromosomes in different
colors [38]. SKY can potentially reveal cryptic
interchromo-somal abnormalities analogous to t(12;21)(p13;q22), which is
a frequent chromosome rearrangement in pediatric
B-lin-eage acute lymphoblastic leukemia. This translocation,
aris-ing from the juxtaposition of similarly banded regions, can be
recognized microscopically only by FISH [1,4]. Recently, 2
series of 20 and 17 AML patients with normal karyotypes
have been analyzed by SKY with no cryptic rearrangement
found [39,40]. Thus, it is unlikely that aberrations
unde-tectable by standard banding methods will be found by
FISH-based techniques using chromosome painting probes in a
large proportion of cytogenetically normal AML patients.
Instead, leukemic blasts of some patients with a normal
karyotype may harbor genetic abnormalities discernible
only by molecular techniques such as RT-PCR or Southern
blot analysis. For instance, approximately 11% of adults with
de novo AML and a normal karyotype display
rearrange-ments of the
MLL
gene (also called
ALL1
,
HRX,
or
Htrx1
)
detectable by Southern blot analysis [41,42]. In all cases with
adequate material for additional molecular analysis, the
MLL
gene rearrangement was a result of a partial tandem
duplication (PTD) of a segment of the gene, with no
evi-dence for involvement of another gene [42]. In another
study, comprising patients with both de novo and secondary
AML, the incidence of PTD was lower, 6% of
cytogeneti-cally normal patients [43]. Additional submicroscopic
genetic changes in AML include dominant-negative
muta-tion of the tumor suppressor gene
C/EBP
a
, reported in 24%
of AML M2 patients with a normal karyotype [44], and point
mutations in the
CBFA2
(
AML1
or
PEBP2
a
B
) gene [45]. It
is plausible that other gene mutations contributing to
leuke-mogenesis in karyotypically normal AML patients will be
discovered in the future.
Among the microscopically detectable chromosomal
rearrangements, the more important ones appear to be
those that are seen recurrently, can occur as the sole
abnor-mality at least in some patients, or are rarely or never found
in other types of hematologic and nonhematologic
malig-nancies. These rearrangements are called primary
aberra-tions and are presumed to play an important role in the
early stages of leukemogenesis [5]. Table 1 lists those
pre-sumed primary abnormalities that have already been
char-acterized molecularly. They are almost exclusively balanced
rearrangements, reciprocal translocations, and inversions,
which involve relocation of chromosomal segments
between chromosomes or within a chromosome but do not
lead to visible loss or gain of chromosomal material. At the
DNA level, however, some such seemingly balanced
aber-rations may be more complex and involve multiple DNA
breaks and further submicroscopic rearrangements of
seg-ments within the genes altered by a given translocation or
inversion [46,47]. In addition to those listed in Table 1,
sev-eral other balanced cytogenetic abnormalities have been
detected recurrently in AML patients, but so far the genes
affected by their creation are unknown. Three such
recip-rocal translocations, each reported in more than 10
patients, are presented in Table 2; the current list of other,
less frequent AML-associated balanced rearrangements
can be found in Mrózek et al [48].
It has been established that most reciprocal
transloca-tions and inversions in AML result in the fusion of genes
that normally are involved directly or indirectly in the
regu-lation of blood cell development [1,4]. Abnormal protein
products of the fusion genes, which are frequently
transcrip-tion factors, have been shown to be capable of dysregulating
proliferation, differentiation, or apoptosis (programmed cell
death) of blood cell precursors [1-4]. Similar effects may be
brought about by loss or/and mutation of tumor suppressor
genes (TSGs), which are presumed consequences of
unbal-anced aberrations that lead to the loss of a whole
chromo-some or a chromosomal segment [1,2,4,5]. To date, however,
the actual TSGs affected by AML-associated deletions,
isochromosomes, unbalanced translocations, and
mono-somies, the more common of which are presented in Table 2,
have not been identified. The only exception is the
TP53
gene found to be inactivated in many patients with AML
(and with myelodysplastic syndrome [MDS]) harboring
deletions or unbalanced translocations leading to the loss of
17p [49]. Alternatively, TSGs located in chromosomal
regions rarely deleted in AML, eg, the cyclin-dependent
kinase inhibitor
p15
INK4Bgene residing at 9p21, may also be
inactivated with high frequency in both adult and childhood
AML through an epigenetic mechanism, such as
hyperme-thylation of CpG islands (i.e., regions of DNA rich in CpG
dinucleotides) in the promoter region of the gene [50].
In contrast to the balanced aberrations, the molecular
mechanism whereby gain of an entire copy of a chromosome
(trisomy) contributes to leukemogenesis is essentially
unknown. To date, only trisomy 11 has been consistently
associated with a specific molecular defect, in this case a
PTD of the
MLL
gene [51].
Although as many as 55% of cytogenetically aberrant
AML patients have only 1 chromosomal abnormality in
their marrow karyotype [5], such an aberration is not the
sole genetic alteration sufficient for transformation of a
nor-mal stem cell into a leukemic blast. Malignant
transforma-tion is a multistep process involving accumulatransforma-tion of several
genetic rearrangements, both those detectable by
cytoge-netic analysis (primary aberrations and, accompanying them,
secondary chromosomal changes) and those discernible by
molecular genetic methods only, as well as epigenetic events
such as hypermethylation of the regulatory regions of TSGs
resulting in their inactivation [4]. This process has been
demonstrated in a recent study in mice, which has provided
experimental evidence that the
Cbf-MYH11
fusion gene can
block myeloid differentiation and predispose to leukemia.
The gene does not instigate leukemogenesis by itself,
how-ever; the acquisition of additional, not yet known, mutations
is required [52].
3. Prognostic Relevance of Cytogenetic Findings
in AML
It has now been well established that results of
cytoge-netic analysis at diagnosis provide important prognostic
information in AML. It is worthy to note that although both
molecular genetic methods (RT-PCR, Southern blot
analy-sis) and FISH are now widely available for detection of
Table 1.
Chromosomal Aberrations in Acute Myeloid Leukemia That Have Been Characterized at the Molecular Level*
Aberration Gene
Affecting the EVI1gene at 3q26
inv(3)(q21q26)† EVI1
t(3;3)(q21;q26)†,‡ EVI1
Involving the NPMgene at 5q34
t(3;5)(q25;q34)§ MLF1-NPM
Involving the MOZgene at 8p11
inv(8)(p11q13)i MOZ-TIF2
t(8;16)(p11;p13)† MOZ-CBP
t(8;22)(p11;q13)i,¶ MOZ-EP300
Involving the nucleoporin genes
CANat 9q34 or NUP98at 11p15
t(6;9)(p23;q34)† DEK-CAN
t(7;11)(p15;p15)† HOXA9-NUP98
inv(11)(p15q22)i,¶ NUP98-DDX10
t(11;20)(p15;q11)i NUP98-TOP1
Involving the ABLgene at 9q34
t(9;22)(q34;q11)#,** ABL-BCR
Involving the CLTHgene at 11q14
t(10;11)(p11-15;q13-23)† AF10-CLTH
Involving the MLLgene at 11q23
t(1;11)(p32;q23)§,** AF1P-MLL t(1;11)(q21;q23)§,** AF1Q-MLL t(2;11)(p21;q23)§,** MLL t(4;11)(q21;q23)§,** AF4-MLL t(6;11)(q21;q23)i,** AF6q21-MLL t(6;11)(q27;q23)†,** AF6-MLL t(9;11)(p22;q23)††,** AF9-MLL t(9;11)(q21-22;q23)i,** MLL ins(10;11)(p11;q23q13-24)i,** MLL t(10;11)(p11-13;q13-23)§,** AF10-MLL t(10;11)(q22;q23)¶,i,** MLL +11† MLL t(11;11)(q13;q23)i,** MLL t(11;15)(q23;q14-15)¶,i,** MLL t(11;16)(q23;p13)§,** MLL-CBP t(11;17)(q23;q12-21)§,** MLL-AF17 t(11;17)(q23;q23)i,** MLL t(11;17)(q23;q25)§,** MLL-AF17q25 t(11;19)(q23;p13.1)†,** MLL-ELL t(11;19)(q23;p13.3)†,** MLL-ENL t(11;22)(q23;q11)i,¶,** MLL-AF22 t(11;22)(q23;q13)i,¶,** MLL-EP300 t(X;11)(q13;q23)i,** AFX1-MLL t(X;11)(q22-24;q23)i,** MLL
Involving the ETV6gene at 12p13
t(3;12)(q26;p13)¶,i ETV6 t(4;12)(q11-12;p13)§ BTL-ETV6 t(5;12)(q31;p13)i ACS2-ETV6 t(7;12)(p15;p13)¶,i ETV6 t(7;12)(q36;p13)¶,i ETV6 t(12;13)(p13;q12)i ETV6 t(12;22)(p12-13;q11-13)¶,i ETV6-MN1
Involving the core binding factor genes
CBFβat 16q22 or CBFA2at 21q22 inv(16)(p13q22)††,** MYH11-CBFb t(16;16)(p13;q22)†,** MYH11-CBFb t(3;21)(q26;q22)§ EAP, MDS1,EVI1,CBFA2 t(8;21)(q22;q22)††,‡‡ CBFA2T1-CBFA2 t(16;21)(q24;q22)i MTG16-CBFA2 t(17;21)(q11.2;q22)¶,i CBFA2 Continued
Table 1.
Continued Aberration GeneInvolving the RARagene at 17q12-21
t(5;17)(q35;q12-21)¶,i,** NPM-RARa
t(11;17)(q23;q12-21)i,** PLZF-RARa
t(15;17)(q22;q12-21)††,** PML-RARa
Involving the ERGgene at 21q22
t(16;21)(p11;q22)† FUS-ERG
*Data from reference 92. Additional data from references 72 and 93-98. Chromosomal aberrations disrupting the same or related gene are grouped together. Within a given group, aberrations are arranged according to the numerical order of the first chromosome involved. Each aberration is presented only once.
†Reported in 26-100 patients.
‡Also interpreted as ins(3;3)(q21;q21q26). §Reported in 6-25 patients.
iChromosomal aberration reported in 5 patients or fewer. ¶To date, not reported recurrently as a solitary aberration. #Reported in 101-200 patients.
**DNA probes for fluorescence in situ hybridization detecting rearrangements of genes (or 1 of the 2 genes) affected by a given aber-ration available commercially.
††Reported in >200 patients.
‡‡Recurring 3-way variant translocations involving 5q31, 12q13, 17q23, and 20q13 also reported.
many recurrent chromosomal aberrations in AML [1,4,37],
the vast majority of data correlating genetic features of
leukemia with the clinical outcome have been obtained from
studies using standard cytogenetic analysis as the primary
investigative tool. Thus, with the exception of t(15;17)/
PML-RAR
a
-positive acute promyelocytic leukemia (APL),
prospective investigations need to test whether conclusions
reached by clinical-cytogenetic studies hold up if only
molec-ular techniques are used for detection of chromosome
changes. This future testing is especially important in light of
significant discrepancies between results of cytogenetic and
RT-PCR analyses in some recent retrospective series [33,53].
Likewise, the clinical applicability of emerging microchip
array technology, which will likely make possible rapid
detec-tion of all molecularly characterized genetic rearrangements
in AML simultaneously [37], will have to be verified before it
can become part of the management of patients with AML.
The significance of the karyotype as an independent
deter-minant of outcome was demonstrated conclusively for the first
time in a large, prospective, multicenter study at the Fourth
International Workshop on Chromosomes in Leukemia
(IWCL) [8]. This study and its first follow-up, the Sixth IWCL
[9], corroborated earlier observations that AML patients with
a normal karyotype (designated NN) were more likely to
suvive longer than patients with a mixture of abnormal and
normal (residual) mitotic cells (AN) or those with abnormal
cells only (AA). However, there was no significant difference
in survival between AN and AA patients [9], and the
proba-bility of their achieving complete remission (CR) was not
dependent on whether normal metaphases were present [8].
In the multivariate analysis of survival, when the other main
risk factors in AML such as age, sex, and
French-American-British classification subtype were also considered, the
NN-AN-AA classification was found to have an independent
prognostic significance in both the group of 656 patients with
de novo AML and the subset of 305 patients who received
more intensive induction treatment with cytarabine and an
anthracycline [9]. Analogous results have been obtained in 2
other studies of adults with de novo AML [11,15]. However, 1
group has not confirmed the prognostic value of the
NN-AN-AA classification, perhaps because more than one-half of
patients in their AA category had the prognostically favorable
t(8;21) [28].
Table 2.
More Common Chromosomal Aberrations in Acute Myeloid Leukemia Not Yet Characterized Molecularly*
Balanced aberrations t(1;3)(p36;q21)† t(1;22)(p13;q13)‡,§ t(3;5)(q21;q31)†
Unbalanced chromosomal rearrangements
Resulting in loss of a chromosome or chromosomal segmenti del(1)(q21)† del(2)(p21-23)† –5† del(5)(q12-31-q31-35)¶,# del(6)(q13-24-q21-27)§ –7¶ del(7)(q11-34-q22-36)¶,** –9† del(9)(p21)† del(9)(q11-22-q21-34)††,‡‡ del(10)(p12)† del(11)(p11-12-p14-15)§ del(11)(q13-23-q22-25)††,§§ del(12)(p11-13)†† del(13)(q11-22-q14-34)§ del(16)(q21-22-q24)§ del(17)(p11-13)§ del(20)(q11-13)††, i i –21† –Y§
Resulting in simultaneous loss and gain of a chromosomal segment der(1;7)(q10;p10)§,¶¶ i(7)(q10)† Continued
Table 2.
Continued i(11)(q10)† i(13)(q10)† i(14)(q10)† i(17)(q10)§ i(21)(q10)† idic(X)(q13)†Resulting in gain of a chromosome or chromosomal segment +i(1)(q10)† +4§ +6† +8¶ +9† +10† +i(12)(p10)† +13§ +14† +19† +21§ +22†
*Data from references 5, 92, and 99. Only aberrations reported as solitary chromosomal changes in at least 2 patients with AML are included. Within a given category, abnormalities are arranged accord-ing to the numerical order of the chromosome(s) involved.
†Chromosomal aberration reported in 6-25 patients. For numerical aberrations (monosomies and trisomies), footnotes †, §, ¶, and †† indi-cate the numbers of patients harboring a particular aberration as a sole abnormality only; for structural aberrations, the numbers provided refer to all patients, irrespective of whether a given aberration is isolated or not.
‡Thus far detected exclusively in children, mostly with AML M7. §Reported in 26-100 patients. (See † for numbers of patients har-boring a particular aberration.)
iAlthough many deletions are reported as terminal, they are gener-ally regarded as being interstitial.
¶Reported in >200 patients. (See † for numbers of patients harbor-ing a particular aberration.)
#del(5)(q13q33) the most common aberration. **del(7)(q22) the most common aberration.
††Reported in 101-200 patients. (See † for numbers of patients har-boring a particular aberration.)
‡‡del(9)(q22) the most common aberration. §§del(11)(q23) the most common aberration. i idel(20)(q11) the most common aberration. ¶¶Reported also as der(1)t(1;7)(p11;p11).
It appears that prognostic relevance of the presence or
absence of residual, normal metaphase cells in karyotypically
aberrant AML patients depends on the kind of chromosomal
aberrations found in leukemic blasts. Ghaddar et al [54]
reported no difference in CR rate, CR duration (CRD), and
survival between AN and AA patients who had either inv(16)
or t(8;21). There was also no difference in CRD between AN
and AA patients with t(15;17). The latter finding was
con-firmed in a series of t(15;17)-positive APL patients treated by
chemotherapy alone, without
all-trans
-retinoic acid (ATRA),
in which no difference in CR rate, event-free survival, and
overall survival between AN and AA patients was found [55].
In contrast, when AML patients with –5, del(5q), –7, del(7q),
or +8 at diagnosis were combined into 1 subset, the clinical
outcome of AN patients was significantly better than that of
AA patients who did not have any normal mitoses [54].
Another system for classifying karyotypes, the complexity
classification, was also found at the Sixth IWCL to represent
an independent prognostic factor [9]. Patients with very
complex karyotypes—ie, when more than 5 chromosomes
were rearranged in the abnormal clone—had the shortest
survival, whereas those with either normal karyotypes or an
abnormal clone or clones involving 2 to 5 chromosomes
sur-vived longest [9]. In a smaller study, AML patients with a
complex karyotype, specified as containing 3 or more clonal
chromosomal aberrations, had a significantly lower CR rate
and shorter survival than those of patients with a normal
karyotype or patients with inv(16), t(8;21), t(15;17), or 1 or 2
other aberrations [16]. A complex karyotype, also defined as
containing at least 3 aberrations, was predictive of shorter
survival in a group of patients aged 56 years or older, but not
in patients younger than 56 years, in a series of more than
200 adults with de novo AML [26]. On the other hand, in the
largest cytogenetic study reported to date, comprising 1612
AML patients younger than 56 years, including 340 children,
complex karyotypes containing “at least 5 unrelated
cytoge-netic abnormalities” were associated with a CR rate
signifi-cantly lower, relapse risk signifisignifi-cantly higher, and overall
sur-vival significantly shorter than those of patients with a
normal karyotype [18].
Although the aforementioned general systems for
classi-fying cytogenetic results may be useful in some groups of
patients with AML, the most important prognostic
informa-tion is gained from detecinforma-tion of specific chromosomal
aber-rations. At the Fourth IWCL, significant differences in CR
rate, CRD, and overall survival time were shown when the
716 patients were classified by karyotype in a prioritized
schema, first according to the presence of t(8;21); then
t(15;17), –5 or del(5q), –7 or del(7q); simultaneous presence
of –5 or del(5q) and –7 or del(7q); followed by abnormalities
of 11q, +8, and +21. The remaining patients were classified
according to the ploidy level (hypodiploid, pseudodiploid,
diploid [normal], and hyperdiploid). Karyotypes were
inde-pendent prognostic factors for duration of first CR and of
overall survival in the group of 305 adequately treated
patients [8]. In the follow-up studies of the Fourth IWCL, a
group comprising patients with inv(16)(p13q22) and
del(16)(q22) was added, all cases with numerical and/or
struc-tural abnormalities of chromosomes 5 and 7 were combined
into a single group, and patients with +8 and +21 were
included in the hyperdiploid group [8-10,56].The multivariate
analyses performed at the third follow-up of the Fourth
IWCL, which then comprised 628 patients with primary
AML and a median follow-up of 14.7 years for living patients,
confirmed that karyotype remained an independent
predic-tor of survival for all patients and for the 291 patients who
received induction therapy considered as standard by
mod-ern criteria [10]. Similarly, other studies in which specific
cyto-genetic findings were categorized in various ways have
con-firmed that karyotype represents an independent prognostic
determinant for attainment of CR [11-13,15,19], for CRD
[11,15], and for overall survival time [14-16,57].
In most studies of adults with de novo AML, the highest
CR rates, the longest CRD, and overall survival time have
been associated with t(8;21) and inv(16) (Table 3). Both of
these chromosomal aberrations are related at the molecular
level because t(8;21) disrupts a gene encoding the subunit
a
and inv(16) disrupts a gene encoding the subunit
b
of
core-binding factor (CBF). CBF is a transcription factor involved
in regulating a number of genes involved in hematopoiesis
and is necessary for normal development of the
hemato-poietic system [58]. The chimeric proteins encoded by fusion
genes
CBFA2T1-CBFA2
and
MYH11-CBF
b
are both able to
repress CBF-mediated transcriptional activation of target
genes in a dominant fashion [58], and this ability may trigger
a common leukemogenic pathway. The blasts carrying either
t(8;21) or inv(16) appear to be more sensitive to currently
used treatment regimens than blasts with other aberrations,
although the molecular basis of a good response to
chemo-therapy of patients with CBF leukemia has not yet been
elu-cidated. Their superior response may arise from an enhanced
sensitivity of the blasts to cytarabine, which, together with
anthracyclines, constitutes a mainstay of current
chemo-therapy for AML. A significant increase in in vitro
incorpora-tion of cytarabine into nuclear DNA and cytarabine-induced
apoptosis of cells from patients with inv(16) compared with
blasts from patients with other chromosomal rearrangements
or a normal karyotype has been recently reported [59].
It has been demonstrated that intensive postremission
therapy with high-dose cytarabine (HDAC) in adults with de
novo AML and t(8;21), inv(16)/t(16;16) or a normal
kary-otype, but not in those with other aberrations, improves their
outcome substantially [17]. The HDAC intensification
treat-ment is especially effective in patients with t(8;21). As shown
by the third follow-up of the Fourth IWCL, no patient with
t(8;21) who attained a CR survived continually disease-free
for 10 years in the absence of HDAC intensification. In
con-trast, 89% of complete responders who were administered
HDAC on the Cancer and Leukemia Group B (CALGB)
8525 protocol were estimated to be cured using a Farewell
Mixture Model [10]. Another CALGB study has indicated
that t(8;21)-positive patients who receive the highest
cumula-tive dose of cytarabine in the course of intensification
treat-ment benefit the most [60]. The projected 5-year disease-free
survival (71% versus 37%) and overall survival (76% versus
44%) rates were superior in patients who were given 3 or 4
cycles of HDAC compared with those who received 1 cycle
only of HDAC followed by sequential treatments with
cyclophosphamide/etoposide and mitoxantrone/diaziquone
with or without filgrastim [60]. Notably, the patients assigned
to receive 3 or 4 cycles of HDAC did not differ from those
assigned to receive only 1 cycle with regard to pretreatment
factors previously reported to confer worse prognosis in
patients with t(8;21), such as absolute granulocyte count
greater than 2
3
10
9/L, leukocyte count more than 20
3
10
9/L, the presence of granulocytic sarcoma, expression of the
neural cell adhesion molecule CD56 on leukemic blasts, or
secondary chromosomal aberrations additional to t(8;21),
including del(9q) and loss of chromosome Y in males or
chro-mosome X in females [60].
Among patients with inv(16)/t(16;16), treatment with
HDAC appears to lower the risk of development of
intra-cerebral myeloblastoma [61], thus making prophylactic
cen-tral nervous system irradiation or intrathecal chemotherapy
unnecessary. Nevertheless, despite the generally good
prog-nosis of adults positive for inv(16) and its improvement by
HDAC, not all such patients are cured. One relatively small
study suggested that treatment results are better in patients
who in addition to inv(16) harbor a submicroscopic deletion
of the gene for multidrug resistance–associated protein
(MRP), located proximally to the short-arm breakpoint of
the inversion, at 16p13.1 [62]. However, 3 subsequent
stud-ies [63-65], including the most recent one in which the
patients received uniform induction and consolidation
treatment with HDAC and mitoxantrone [65], have not
con-firmed the favorable influence of MRP gene deletions on
prognosis. Additionally, the treatment outcome of patients
with inv(16)/t(16;16) does not seem to be affected by the
presence of various secondary aberrations [18,66-68] that
may accompany inv(16) in more than 40% of patients [69].
Thus, other factors are likely responsible for the clinical
het-erogeneity within this subset of AML.
Table 3.
Associations Between Selected Recurrent Chromosomal Findings and Clinical Outcome in Adults With De Novo Acute Myeloid Leukemia* Complete Remission Survival
Chromosome Aberration† Rate, % (n) Median, mo Probability, % (y)‡ Median, mo Probability, % (y)‡ t(8;21)(q22;q22)A 93 (563) 9-60+ ~16 (3) to 71 (5) 17-95+ 24 to 69 (5) t(16;21)(p11;q22)B 90 (20) NA NA 13 NA inv(16)(p13q22)C 87 (367) 15-48+ ~33 (3) to 62 (5) 12-77 38 (4) to ~76 (5) t(6;11)(q27;q23)D 85 (26) 8 NA 12 4 (2)§ t(9;11)(p22;q23)E 79 (24) 11 37 (5) 13 38 (5) t(11;19)(q23;p13.1)F 79 (19) NA NA NA 26 (2)§ t(15;17)(q22;q12-21)G 78 (559) 13-30 ~15 (3) to 63 (5) 8-33 ~8 (3) to 63 (5) NoneH 76 (1929) 7-17 10-47 (5) 7-31 ~7 (3) to 42 (5) del(7q)J 75 (32) NA 41 (5) NA 23 (5) +8 (sole)K 73 (134) 14-35 16 (3) to 33 (5) 11-21 17 (3) to 27 (5) Abnormalities of 11q23L,i 63 (125) 6-12 0 (3) to 33 (5) 2-18 0 (3) to 11 (5) +11 (sole)M 61 (38) 17 17 (4) 14 15 (4) del(5q)N 57 (28) NA 15 (5) NA 11 (5) –7O¶ 56 (66) NA 20 (5) NA 10 (5) +8P# 53 (88) 8-24 NA 9-11 0 (5) to 19 (3) Abnormalities of 12pR 47 (38) NA NA NA 11 (2)§ del(20q) or –20S 46 (11) 7 NA 9 17 (3) +13 (sole)T 43 (40) NA NA 3 NA –5U 42 (26) NA 10 (5) NA 4 (5) Unbalanced abnormalities of 11q23V,** 41 (29) 5-6 NA 2 NA t(9;22)(q34;q11)W 38 (42) 6 NA 7 NA inv(3)(q21q26)/t(3;3)(q21;q26)X†† 30 (27) 6 NA 9 0 (3)
*Some studies also included 15% to 18% of patients diagnosed with MDS [79,120], or 5% to 37% of patients with secondary acute myeloid leukemia (ie, following an antecedent hematologic disorder or chemo- or radiotherapy for prior malignancy) [11,18,27,67,68,79,104,109,111,114], or 2% to 21% of children with AML [12,13,18,21,86,101,103,104,106,110-113].
†Aberrations are arranged according to the associated average complete remission (CR) rate (from the highest to the lowest), calculated from data on all patients with a given aberration reported in the studies referenced. A superscript capital letter placed after a given abnormality denotes reference numbers identifying articles containing clinical outcome data on patients with this aberration, as follows: A[11,12,18,21,25-28,100-106], B[101,102], C[12,18,21,25-27,66-68,86,105,109], D[110], E[78], F[111], G[11-13,15,18,21,25-27,55,86,112,113], H[11-13,15,16,18,21,25-27,105], J[18], K[18,26,28,84-86], L[12,13,15,25-27,78,79,114], M[21,28,51,87,115,116], N[18], O[13,18], P[11-13,15,16,27], R[117], S[27,118], T[119,120], U[18], V[114,121], W[11,12,21,26-28,122,123], X[27,74,124,125].
‡For a given aberration, only the lowest and the highest probability of remaining in CR or surviving, respectively, are provided. ~ denotes data obtained from Kaplan-Meier plots in reference. Numbers in parentheses indicate the time points in years of when the probability was determined. NA, data not available.
§Actual percentage of patients alive at a given time point.
iIn most studies, this group contains all types of translocations involving band 11q23, including t(9;11)(p22;q23), and deletions of 11q23, except in Mrózek et al [78], where t(9;11) and del(11q) have been excluded.
¶There is no clear distinction between –7 as a sole abnormality and as a secondary change accompanying other aberrations. #There is no clear distinction between +8 as a sole abnormality and as a secondary change.
**Includes 16 cases with del(11q) and 13 cases with unbalanced translocations with known or unknown partner chromosomes.
Patients with t(15;17) represent another group
character-ized by unique morphologic features and presenting clinical
features and a good prognosis. The average CR rate for
adults with t(15;17) in Table 3 is only 78%, but this has been
calculated from studies that predominantly involved APL
patients treated with chemotherapy alone, without ATRA.
The addition of ATRA to the induction regimen has been
reported to raise the CR rate in such patients to between
85% and 91%, and to significantly prolong disease-free and
overall survival [32,70]. The importance of detecting t(15;17)
in all APL patients is underscored by results of a recent
intergroup study in which none of the 5 patients considered
to have “APL-like” marrow morphology, but who were
PML-RAR
a
-
negative (and hence did not have the t[15;17]),
achieved a CR when treated with ATRA [71].
Correspond-ingly, patients with APL-like AML and t(11;17) (q23;q21)
are not responsive to ATRA even at high doses; they also
have a poor prognosis regardless of whether chemotherapy
or ATRA is used as induction therapy [72].
Adults with an entirely normal karyotype seem to have
an intermediate prognosis. Their CRD and survival are
shorter than those of adequately treated patients with
t(8;21), inv(16), or t(15;17) but are longer than patients with
unfavorable chromosomal aberrations (Table 3). However,
this group is highly heterogeneous and is likely composed of
subsets with varying prognoses. For instance, the presence of
a submicroscopic PTD of the
MLL
gene identifies a
sub-group of karyotypically normal patients characterized by a
significantly shorter CRD [42,43] and overall survival [43]
than patients with a normal karyotype and the germline
MLL
. Another feature associated with worse prognosis of
adults with de novo AML and a normal karyotype may be
the presence of erythroblastic and/or megakaryoblastic
dys-plasia (EMD) in the diagnostic marrow. In a relatively small
study, cytogenetically normal patients with EMD had a
signi-ficantly lower CR rate and a shorter event-free and overall
survival than did similar patients without EMD [73]. Future
studies will likely discover other factors, including
submicro-scopic gene mutations, that can affect the treatment outcome
of AML patients with normal cytogenetics.
A number of chromosomal aberrations have been
repeat-edly associated with a poor prognosis. These include inv(3)
(q21q26) or t(3;3)(q21;q26), del(5q) or –5, –7, t(9;22)
(q34;q11), and abnormalities of 12p. Prolonged CRD and long
survival are uncommon in patients with these aberrations
(Table 3). Of note, in the case of inv(3) and t(3;3), it is the
presence of microscopically identifiable chromosomal
aberra-tions, not inappropriate overexpression of the
EVI1
gene,
detectable by RT-PCR in both patients with inv(3)/t(3;3) and
those without these aberrations, that has adverse prognostic
significance [74]. Deletions of 7q occurring concurrently with
del(5q) or –5 or as part of a complex karyotype have also
been associated with poor prognosis. In contrast, the outcome
of patients with del(7q) in the absence of unfavorable
cytoge-netic features, ie, a complex karyotype, abnormalities of 3q or
del(5q)/–5, did not differ significantly from that of patients
with a normal karyotype in a study reported by Grimwade et
al [12]. Their findings are consistent with earlier observations
that patients with del(7q) without concurrent aberrations of
chromosome 5 may have prolonged survival [26,56].
A recent study indicates that prognosis of AML/MDS
patients with –5/del(5q) and/or –7/del(7q) may also be
influ-enced by the stability of the leukemic karyotype. Estey et al
[75] analyzed treatment outcome of 400 patients with the
aforementioned aberrations [excluding patients with
con-comitant inv(16) or t(8;21)] who were diagnosed with de
novo AML, AML secondary to an antecedent hematologic
disorder (AHD), refractory anemia with excess of blasts, or
refractory anemia with excess of blasts in transformation. In
general, the clinical outcome of this group was poor, with a
median survival of 4 months. However, although the CR
rates were the same (40%), the disease-free survival once in
CR and overall survival were significantly longer for
patients with only 1 abnormal clone versus those with the
less stable karyotype containing 2 or more clones. By using
2 other factors to stratify the patients, ie, presence or absence
of residual normal cells and presence or absence of AHD,
Estey et al recognized a small (10%) subset of patients with
–5/del(5q) and/or –7/del(7q) with a better prognosis,
equiv-alent to that of similarly treated patients with a normal
karyotype. Patients in this subset had only 1 abnormal clone,
at least 1 normal mitotic cell, and no history of AHD [75].
These results should be corroborated in more homogeneous
patient populations.
Patients with other recurrent aberrations have been
vari-ously placed in either the intermediate [18,57,76] or
unfa-vorable [10,17,77] prognostic groups. This distinction, to a
certain extent, reflects the infrequency of many recurrent
abnormalities in AML that has thus far precluded reliable
assessment of their prognostic importance. Furthermore,
certain cytogenetic categories may be heterogeneous. Once
an adequate number of uniformly treated patients are
stud-ied, they may be further divided into subgroups with
dis-parate prognoses. For instance, in our study of treatment
outcome in adults with de novo AML and balanced
abnor-malities involving band 11q23 [78], patients with t(9;11)
(p22;q23), who in most earlier studies had been grouped
together with patients with other 11q23 aberrations [11,12,
15,25-27,79], had a significantly longer CRD, event-free
sur-vival, and overall survival than adults with translocations
between 11q23 and partner chromosomes other than 9p22
[78]. Likewise, patients with t(9;11) had a better outcome
than those with t(10;11)(p12;q23) in another study, although
the difference was not statistically significant [18]. In most
[80,81] but not all [82] series of childhood AML, t(9;11)
con-ferred a significantly better prognosis than other types of
11q23 anomalies.
Thus, regardless of age, detection of the
MLL
gene
rearrangement by Southern blot analysis alone, without
identification of the 11q23 partner chromosome by standard
cytogenetic analysis, FISH, or RT-PCR, is not sufficient for
predicting the patients’ clinical behavior [78]. Notably, the
prognosis of adults with t(9;11) does not seem to be
unfa-vorably influenced by the presence of +8 as a secondary
aberration [78], nor does it correlate with
immunopheno-typic features of leukemic cells, including lymphoid antigen
expression [83]. Our preliminary findings suggest that
patients with de novo AML and t(9;11), but not those with
other 11q23 translocations, may particularly benefit from
intensive postremission therapy in first CR [78]. The efficacy
of intensification regimens containing HDAC alone or in
combination with other drugs, including etoposide, shown to
be especially effective in children with myelomonocytic and
monocytic leukemias, should be assessed prospectively in
adults with t(9;11) and, if confirmed, might become the
ther-apy of choice for patients when stem cell transplantation is
not available [78].
Substantial variation in CR rates (from 29% [12] to 91%
[26]), CRD, and survival rates has been observed among AML
patients with +8 (Table 3). In some reports [11-13,15,16,27],
this cytogenetic group included both patients with isolated
+8 and those who in addition to +8 had other aberrations
that may have affected response to treatment and outcome.
Selective detection of +8 by interphase FISH is not adequate
to determine prognosis, as has been shown by recent studies
reporting large differences in outcome between patients
with solitary +8 and those in whom +8 occurred in addition
to aberrations conferring either favorable or adverse
prog-noses [18,84]. However, the differences in outcome among
studies are also notable when patients with isolated +8 only
were included [18,26,84-86]. This variability could be
associ-ated with differences in the age of the patients analyzed by
different groups. Byrd et al [85] have shown that the CR rate
of patients older than 60 years with solitary +8 is significantly
lower than that of younger patients (40% versus 88%;
P
=
.004), as is their overall survival (median, 4.8 months versus
17.5 months;
P
= .01). Patients younger than 35 years,
includ-ing a substantial number of children, dominated among
patients with +8 in the study of Grimwade et al [18], who
reported a relatively good outcome for patients with isolated
+8. The adverse effect of older age on treatment outcome
was also observed in adults with isolated +11 [87] and in
patients constituting the “poor prognosis” group [ie, patients
with der(1;7)(q10;p10), inv(3), del(5q)/-5, –7, t(9;22), or
com-plex karyotypes] and the “intermediate prognosis” group [ie,
patients with a normal karyotype or aberrations other than
the aforementioned unfavorable ones or favorable t(8;21),
inv(16), and t(15;17)] in a population-based series of 372
adults with AML [76]. On the other hand, a relatively good
prognosis for patients belonging to a “favorable” group did
not deteriorate with age, and the median survival was even
longer in the group of oldest patients (65 to 74 years) than in
patients aged 50 to 64 and 20 to 49 years [76].
4. Conclusions
The prognostic significance of several of the more
fre-quent karyotypic aberrations has now been well established.
Recently, cytogenetic findings have been integrated into a
prognostic index applicable in risk-directed therapy
decision-making for younger patients with AML [57]. However, many
less common aberrations, whose individual impact on the
clinical outcome is at present unknown, have been combined
into 1 prognostic category, which may be an
oversimplifica-tion. Moreover, novel chromosomal aberrations are still being
discovered in AML patients, using both standard cytogenetic
analysis and molecular-cytogenetic techniques such as FISH,
SKY, and rainbow cross-species FISH (Rx-FISH) [39,88-90].
Accurate detection of genetic abnormalities becomes even
more important as therapeutic agents designed to target
spe-cific molecular rearrangements associated with recurrent
chromosomal aberrations in AML become available. Such
an agent, STI 571, a protein tyrosine kinase inhibitor that
suppresses proliferation of cells harboring the
BCR-ABL
fusion gene created by t(9;22), has been successfully used to
treat patients with chronic myelogenous leukemia who have
failed interferon therapy [91]. It is well known that
prognos-tic factors in AML depend on the type of induction and,
per-haps to an even greater extent, postremission treatment used
[10,17,60]. An abnormality conferring an adverse prognosis
with 1 therapeutic regimen may lose its unfavorable
prog-nostic impact when another treatment is used. Hence, a clear
need exists for large prospective studies evaluating
associa-tions between karyotype and clinical outcome. Such studies
will facilitate evaluation of the prognostic impact of the less
frequent chromosomal aberrations, both primary and
sec-ondary, whose clinical significance is not yet determined.
Acknowledgments
This work was supported in part by grant 5P30CA16058
from the National Cancer Institute and by the Coleman
Leukemia Research Fund.
References
1. Look AT. Oncogenic transcription factors in the human acute leukemias.Science. 1997;278:1059-1064.
2. Mrózek K, Bloomfield CD. Chromosome aberrations. In: Bertino JR, ed.Encyclopedia of Cancer.Vol. 1. San Diego, CA: Academic Press; 1997:380-391.
3. Stewart AK, Schuh AC. White cells 2: impact of understanding the molecular basis of haematological malignant disorders on clinical practice.Lancet. 2000;355:1447-1453.
4. Caligiuri MA, Bloomfield CD. The molecular biology of leukemia. In: DeVita VT Jr, Hellman S, Rosenberg SA, eds.Cancer: Princi-ples & Practice of Oncology.6th ed. Philadelphia, PA: Lippincott-Raven; 2000. In press.
5. Heim S, Mitelman F.Cancer Cytogenetics.2nd ed. New York, NY: Wiley-Liss; 1995.
6. Mrózek K, Heinonen K, de la Chapelle A, Bloomfield CD. Clinical significance of cytogenetics in acute myeloid leukemia. Semin Oncol. 1997;24:17-31.
7. Harris NL, Jaffe ES, Diebold J, et al. World Health Organization classification of neoplastic diseases of the hematopoietic and lym-phoid tissues: report of the Clinical Advisory Committee meet-ing—Airlie House, Virginia, November 1997. J Clin Oncol. 1999;17:3835-3849.
8. Bloomfield CD, Goldman A, Hossfeld D, de la Chapelle A. Fourth International Workshop on Chromosomes in Leukemia in 1982: clinical significance of chromosomal abnormalities in acute non-lymphoblastic leukemia.Cancer Genet Cytogenet. 1984;11:332-350. 9. Arthur DC, Berger R, Golomb HM, et al. The clinical significance of karyotype in acute myelogenous leukemia.Cancer Genet Cyto-genet. 1989;40:203-216.
10. Bloomfield CD, Shuma C, Regal L, et al. Long-term survival of patients with acute myeloid leukemia. A third follow-up of the Fourth International Workshop on Chromosomes in Leukemia.
Cancer. 1997;80(suppl):2191-2198.
11. Keating MJ, Smith TL, Kantarjian H, et al. Cytogenetic pattern in acute myelogenous leukemia: a major reproducible determinant of outcome.Leukemia. 1988;2:403-412.
12. Schiffer CA, Lee EJ, Tomiyasu T, Wiernik PH, Testa JR. Prognos-tic impact of cytogenePrognos-tic abnormalities in patients with de novo acute nonlymphocytic leukemia.Blood. 1989;73:263-270. 13. Fenaux P, Preudhomme C, Laï JL, Morel P, Beuscart R, Bauters F.
Cytogenetics and their prognostic value in de novo acute myeloid leukaemia: a report on 283 cases.Br J Haematol. 1989;73:61-67. 14. Tashiro S, Kyo T,Tanaka K, et al.The prognostic value of cytogenetic
analyses in patients with acute nonlymphocytic leukemia treated with the same intensive chemotherapy.Cancer. 1992;70:2809-2815. 15. Stasi R, Del Poeta G, Masi M, et al. Incidence of chromosome
abnormalities and clinical significance of karyotype in de novo acute myeloid leukemia.Cancer Genet Cytogenet. 1993;67:28-34. 16. de Nully Brown P, Jurlander J, Pedersen-Bjergaard J, Victor MA,
Geisler CH. The prognostic significance of chromosomal analysis and immunophenotyping in 117 patients with de novo acute myeloid leukemia.Leuk Res. 1997;21:985-995.
17. Bloomfield CD, Lawrence D, Byrd JC, et al. Frequency of pro-longed remission duration after high-dose cytarabine intensifica-tion in acute myeloid leukemia varies by cytogenetic subtype. Can-cer Res. 1998;58:4173-4179.
18. Grimwade D, Walker H, Oliver F, et al. The importance of diag-nostic cytogenetics on outcome in AML: analysis of 1,612 patients entered into the MRC AML 10 trial.Blood. 1998;92:2322-2333. 19. Mehta J, Powles R, Treleaven J, et al. The impact of karyotype on
remission rates in adult patients with de novo acute myeloid leukemia receiving high-dose cytarabine-based induction chemo-therapy.Leuk Lymphoma. 1999;34:553-560.
20. Bloomfield CD, de la Chapelle A. Chromosome abnormalities in acute nonlymphocytic leukemia: clinical and biologic significance.
Semin Oncol. 1987;14:372-383.
21. Tien H-F, Wang C-H, Lin M-T, et al. Correlation of cytogenetic results with immunophenotype, genotype, clinical features, and ras mutation in acute myeloid leukemia: a study of 235 Chinese patients in Taiwan.Cancer Genet Cytogenet.1995;84:60-68. 22. Fischer K, Scholl C, Sàlat J, et al. Design and validation of DNA
probe sets for a comprehensive interphase cytogenetic analysis of acute myeloid leukemia.Blood. 1996;88:3962-3971.
23. Mrózek K, Prior TW, Edwards C, et al. A comparison of cytogenetic and molecular genetic detection of t(8;21)(q22;q22) and inv(16)(p13q22) in adults with de novo acute myeloid leukemia (AML): a Cancer and Leukemia Group B (CALGB) study.Blood. 1998;92(suppl 1):77a. 24. Yunis JJ, Lobell M, Arnesen MA, et al. Refined chromosome study
helps define prognostic subgroups in most patients with primary myelodysplastic syndrome and acute myelogenous leukaemia.Br J Haematol.1988;68:189-194.
25. Marosi C, Köller U, Koller-Weber E, et al. Prognostic impact of karyotype and immunologic phenotype in 125 adult patients with de novo AML.Cancer Genet Cytogenet. 1992;61:14-25.
26. Dastugue N, Payen C, Lafage-Pochitaloff M, et al. Prognostic signi-ficance of karyotype in de novo adult acute myeloid leukemia.
Leukemia. 1995;9:1491-1498.
27. Joventino LP, Stock W, Lane NJ, et al. Certain HLA antigens are associated with specific morphologic and cytogenetic subsets of acute myeloid leukemia.Leukemia. 1995;9:433-439.
28. Weh HJ, Kuse R, Hoffmann R, et al. Prognostic significance of chromosome analysis in de novo acute myeloid leukemia (AML).
Blut. 1988;56:19-26.
29. Hoff PM, Pierce S, Estey E. Comparison of acute myeloid leukemia patients at M.D. Anderson: 1982-1986 vs 1992-1996.
Leukemia.1997;11:1997-1998.
30. Mauritzson N, Johansson B, Albin M, et al. A single-center popula-tion-based consecutive series of 1500 cytogenetically investigated adult hematological malignancies: karyotypic features in relation to morphology, age and gender.Eur J Haematol. 1999;62:95-102. 31. Krauter J, Peter W, Pascheberg U, et al. Detection of karyotypic
aberrations in acute myeloblastic leukaemia: a prospective com-parison between PCR/FISH and standard cytogenetics in 140 patients with de novo AML.Br J Haematol. 1998;103:72-78. 32. Burnett AK, Grimwade D, Solomon E, Wheatley K, Goldstone
AH. Presenting white blood cell count and kinetics of molecular remission predict prognosis in acute promyelocytic leukemia treated with all-transretinoic acid: result of the Randomized MRC Trial.Blood. 1999;93:4131-4143.
33. Langabeer SE, Walker H, Gale RE, et al. Frequency of CBFb/MYH11 fusion transcripts in patients entered into the U.K. MRC AML trials.Br J Haematol. 1997;96:736-739.
34. Mitterbauer M, Laczika K, Novak M, et al. High concordance of karyotype analysis and RT-PCR for CBF beta/MYH11 in unse-lected patients with acute myeloid leukemia: a single center study.
Am J Clin Pathol. 2000;113:406-410.
35. Grimwade D, Gorman P, Duprez E, et al. Characterization of cryp-tic rearrangements and variant translocations in acute promyelo-cytic leukemia.Blood. 1997;90:4876-4885.
36. Hackwell SM, Robinson DO, Harvey JF, Ross FM. Identification of false-positive CBFb/MYH11 RT-PCR results.Leukemia. 1999; 13:1617-1619.
37. Raimondi SC. Fluorescence in situ hybridization: molecular probes for diagnosis of pediatric neoplastic diseases. Cancer Invest. 2000;18:135-147.
38. Veldman T, Vignon C, Schröck E, Rowley JD, Ried T. Hidden chro-mosome abnormalities in haematological malignancies detected by multicolour spectral karyotyping.Nat Genet. 1997;15:406-410. 39. Beverloo B, van Drunen E, Smit B, Slater R. Spectral karyotyping:
detection and identification of new chromosomal aberrations in acute leukemia.Cytogenet Cell Genet. 1999;85:36.
40. Mohr B, Bornhäuser M, Thiede C, et al. Comparison of spectral karyotyping and conventional cytogenetics in 39 patients with acute myeloid leukemia and myelodysplastic syndrome.Leukemia. 2000;14:1031-1038.
41. Caligiuri MA, Schichman SA, Strout MP, et al. Molecular rearrangement of the ALL-1 gene in acute myeloid leukemia with-out cytogenetic evidence of 11q23 chromosomal translocations.
Cancer Res. 1994;54:370-373.
42. Caligiuri MA, Strout MP, Lawrence D, et al. Rearrangement of ALL1 (MLL) in acute myeloid leukemia with normal cytogenetics.
Cancer Res. 1998;58:55-59.
43. Schnittger S, Kinkelin U, Schoch C, et al. Screening for MLL tandem duplication in 387 unselected patients with AML identify a prog-nostically unfavorable subset of AML.Leukemia. 2000;14:796-804. 44. Pabst T, Mueller BU, Schnittger S, Behre G, Hiddemann W, Tenen
DG. Dominant negative mutations of the tumor suppressor CCAAT/enhancer binding protein a (C/EBP a): role in acute myeloid leukemia.Blood. 1999;94(suppl 1):624a.
45. Osato M, Asou N, Abdalla E, et al. Biallelic and heterozygous point mutations in the runt domain of the AML1/PEBP2aB gene associated with myeloblastic leukemias.Blood. 1999;93:1817-1824. 46. Strout MP, Mrózek K, Heinonen K, Sait SNJ, Shows TB, Aplan PD. ML-1 cell line lacks a germline MLL locus.Genes Chromosomes Cancer. 1996;16:204-210.
47. Reichel M, Gillert E, Nilson I, et al. Fine structure of translocation breakpoints in leukemic blasts with chromosomal translocation t(4;11): the DNA damage-repair model of translocation. Onco-gene. 1998;17:3035-3044.
48. Mrózek K, Heinonen K, Bloomfield CD. Clinical importance of cytogenetics in acute myeloid leukaemia.Baillieres Best Pract Res Clin Haematol. In press.
49. Lai J-L, Preudhomme C, Zandecki M, et al. Myelodysplastic syn-dromes and acute myeloid leukemia with 17p deletion: an entity characterized by specific dysgranulopoiesis and a high incidence of p53 mutations.Leukemia. 1995;9:370-381.
50. Herman JG, Civin CI, Issa JP, Collector MI, Sharkis SJ, Baylin SB. Distinct patterns of inactivation of p15INK4B and p16INK4A characterize the major types of hematological malignancies. Can-cer Res. 1997;57:837-841.
51. Caligiuri MA, Strout MP, Schichman SA, et al. Partial tandem duplication of ALL1 as a recurrent molecular defect in acute myeloid leukemia with trisomy 11.Cancer Res. 1996;56:1418-1425. 52. Castilla LH, Garrett L, Adya N, et al. The fusion gene Cbfb -MYH11blocks myeloid differentiation and predisposes mice to acute myelomonocytic leukaemia.Nat Genet. 1999;23:144-146. 53. Langabeer SE, Walker H, Rogers JR, et al. Incidence of
AML1/ETO fusion transcripts in patients entered into the MRC AML trials.Br J Haematol. 1997;99:925-928.
resid-ual normal metaphases in acute myelogenous leukemia patients presenting with abnormal karyotype.Leukemia. 1995;9:779-782. 55. Slack JL, Arthur DC, Lawrence D, et al. Secondary cytogenetic
changes in acute promyelocytic leukemia: prognostic importance in patients treated with chemotherapy alone and association with the intron 3 breakpoint of the PML gene: a Cancer and Leukemia Group B study.J Clin Oncol. 1997;15:1786-1795.
56. Swansbury GJ, Lawler SD, Alimena G, et al. Long-term survival in acute myelogenous leukemia: a second follow-up of the Fourth International Workshop on Chromosomes in Leukemia.Cancer Genet Cytogenet. 1994;73:1-7.
57. Wheatley K, Burnett AK, Goldstone AH, et al. A simple, robust, validated and highly predictive index for the determination of risk-directed therapy in acute myeloid leukaemia derived from the MRC AML 10 trial.Br J Haematol. 1999;107:69-79.
58. Löwenberg B, Downing JR, Burnett A. Acute myeloid leukemia.
N Engl J Med. 1999;341:1051-1062.
59. Tosi P, Visani G, Ottaviani E, Testoni N, Pellacani A, Tura S. Inv(16) acute myeloid leukemia cells show an increased sensitivity to cyto-sine arabinoside in vitro.Eur J Haematol. 1998;60:161-165. 60. Byrd JC, Dodge RK, Carroll A, et al. Patients with t(8;21)(q22;q22)
and acute myeloid leukemia have superior failure-free and overall survival when repetitive cycles of high-dose cytarabine are admin-istered.J Clin Oncol. 1999;17:3767-3775.
61. Larson RA, Williams SF, Le Beau MM, Bitter MA, Vardiman JW, Rowley JD. Acute myelomonocytic leukemia with abnormal eosinophils and inv(16) or t(16;16) has a favorable prognosis.
Blood. 1986;68:1242-1249.
62. Kuss BJ, Deeley RG, Cole SPC, et al. Deletion of gene for multidrug resistance in acute myeloid leukaemia with inversion in chromo-some 16: prognostic implications.Lancet. 1994;343:1531-1534. 63. Marlton P, Claxton DF, Liu P, et al. Molecular characterization of
16p deletions associated with inversion 16 defines the critical fusion for leukemogenesis.Blood. 1995;85:772-779.
64. Martinet D, Mühlematter D, Leeman M, et al. Detection of 16p deletions by FISH in patients with inv(16) or t(16;16) and acute myeloid leukemia (AML).Leukemia. 1997;11:964-970.
65. Döhner K, Schlenk RF, van der Reijden BA, Döhner H. Deletion of the multidrug resistance-associated protein (MRP1) gene in acute myeloid leukemia with inversion of chromosome 16 has no prognostic impact.Leukemia. 2000;14:1154.
66. Campbell LJ, Challis J, Fok T, Garson OM. Chromosome 16 abnor-malities associated with myeloid malignancies. Genes Chromo-somes Cancer. 1991;3:55-61.
67. Marlton P, Keating M, Kantarjian H, et al. Cytogenetic and clinical correlates in AML patients with abnormalities of chromosome 16.
Leukemia. 1995;9:965-971.
68. Schoch C, Büchner T, Freund M, et al. Fifty-nine cases of acute myeloid leukemia with inversion inv(16)(p13q22): do additional chromosome aberrations influence prognosis? In: Büchner T, Hid-demann W, Wörmann B, Schellong G, Ritter J, Creutzig U, eds.
Acute Leukemias VI. Prognostic Factors and Treatment Strategies. Berlin, Germany: Springer-Verlag; 1997:11-16.
69. Berger R, Busson-Le Coniat M. Uneven frequencies of secondary chromosomal abnormalities in acute myeloid leukemias with t(8;21), t(15;17), and inv(16).Cancer Genet Cytogenet. 2000;117:159-162. 70. Tallman MS, Andersen JW, Schiffer CA, et al. All-trans-retinoic acid
in acute promyelocytic leukemia.N Engl J Med. 1997;337:1021-1028. 71. Gallagher RE, Willman CL, Slack JL, et al. Association of
PML-RARafusion mRNA type with pretreatment hematologic characteristics but not treatment outcome in acute promyelo-cytic leukemia: an intergroup molecular study. Blood. 1997;90:1656-1663.
72. Melnick A, Licht JD. Deconstructing a disease: RARa, its fusion partners, and their roles in the pathogenesis of acute promyelo-cytic leukemia.Blood. 1999;93:3167-3215.
73. Lemezˇ P, Gáliková J, Haas T. Do de novo acute myeloid leukemias with normal cytogenetics involve two main prognostic categories distinguished by the presence of erythroblastic and/or megakary-ocytic dysplasia? Neoplasma. 2000;47:41-47.
74. Langabeer SE, Rogers JR, Harrison G, et al.EVI1expression in acute myeloid leukaemia.Br J Haematol. 2000;108(suppl 1):69. 75. Estey EH, Pierce S, Keating MJ. Identification of a group of
AML/MDS patients with a relatively favorable prognosis who have chromosome 5 and/or 7 abnormalities.Haematologica. 2000; 85:246-249.
76. Mauritzson N, Johansson B, Albin M, et al. Survival time in a pop-ulation-based consecutive series of adult acute myeloid leukemia: the prognostic impact of karyotype during the time period 1976-1993.Leukemia. 2000;14:1039-1043.
77. Estey E, deLima M, Strom S, Pierce S, Freireich EJ, Keating MJ. Long-term follow-up of patients with newly diagnosed acute myeloid leukemia treated at the University of Texas M.D. Ander-son Cancer Center.Cancer. 1997;80(suppl):2176-2180.
78. Mrózek K, Heinonen K, Lawrence D, et al. Adult patients with de novo acute myeloid leukemia and t(9;11)(p22;q23) have a superior outcome to patients with other translocations involving band 11q23: a Cancer and Leukemia Group B study.Blood. 1997;90: 4532-4538.
79. Cortes J, O’Brien S, Kantarjian H, et al. Abnormalities in the long arm of chromosome 11 (11q) in patients with de novo and sec-ondary acute myelogenous leukemias and myelodysplastic syn-dromes.Leukemia.1994;8:2174-2178.
80. Martinez-Climent JA, Lane NJ, Rubin CM, et al. Clinical and prog-nostic significance of chromosomal abnormalities in childhood acute myeloid leukemia de novo.Leukemia. 1995;9:95-101. 81. Pui C-H, Raimondi SC, Srivastava DK, et al. Prognostic factors in
infants with acute myeloid leukemia.Leukemia. 2000;14:684-687. 82. Raimondi SC, Chang MN, Ravindranath Y, et al. Chromosomal
abnormalities in 478 children with acute myeloid leukemia: clinical characteristics and treatment outcome in a cooperative Pediatric Oncology Group study. POG 8821.Blood. 1999;94:3707-3716. 83. Baer MR, Stewart CC, Lawrence D, et al. Acute myeloid leukemia
with 11q23 translocations: myelomonocytic immunophenotype by multiparameter flow cytometry.Leukemia. 1998;12:317-325. 84. Schoch C, Haase D, Fonatsch C, et al. The significance of trisomy 8
in de novo acute myeloid leukaemia: the accompanying chromo-some aberrations determine the prognosis.Br J Haematol. 1997;99: 605-611.
85. Byrd JC, Lawrence D, Arthur DC, et al. Patients with isolated tri-somy 8 in acute myeloid leukemia are not cured with cytarabine-based chemotherapy: results from Cancer and Leukemia Group B 8461.Clin Cancer Res. 1998;4:1235-1241.
86. Berger R, Bernheim A, Ochoa-Noguera ME, et al. Prognostic significance of chromosomal abnormalities in acute nonlympho-cytic leukemia: a study of 343 patients.Cancer Genet Cytogenet. 1987;28:293-299.
87. Heinonen K, Mrózek K, Lawrence D, et al. Clinical characteristics of patients with de novo acute myeloid leukaemia and isolated tri-somy 11: a Cancer and Leukemia Group B study.Br J Haematol. 1998;101:513-520.
88. Specchia G, Cuneo A, Liso V, et al. A novel translocation t(1;7)(p36;q34) in three patients with acute myeloid leukaemia.Br J Haematol. 1999;105:208-214.
89. Theil KS, Mrózek K, Glasure CE, Caligiuri MA, Bloomfield CD. der(7)t(7;11)(q11.1;q12) as a new non-random abnormality associ-ated with acute myeloid leukemia (AML).Cytogenet Cell Genet. 1999;85:88.
90. Teixeira MR, Micci F, Dietrich CU, Heim S. Cross-species color banding characterization of chromosomal rearrangements in leukemias with incomplete G-band karyotypes.Genes Chromo-somes Cancer. 1999;26:13-19.
91. Druker BJ, Talpaz M, Resta D, et al. Clinical efficacy and safety of an ABL specific tyrosine kinase inhibitor as targeted therapy for chronic myelogenous leukemia [abstract].Blood. 1999;94(suppl 1):368a. 92. Mitelman F, Mertens F, Johansson B. Breakpoint map of recurrent
chromosome aberrations. National Center for Biotechnology Information, National Library of Medicine. Available at: http:// www. ncbi.nlm.nih.gov/CCAP/mitelsum.cgi. Accessed July 12, 2000. 93. Chaffanet M, Gressin L, Preudhomme C, Soenen-Cornu V,
