Emergence of new clonal abnormalities following interferon-alpha induced complete cytogenetic response in patients with chronic myeloid leukemia: report of three cases

Characterisation of clonal Philadelphia-negative cytogenetic abnormalities in a large cohort of chronic myeloid leukaemia

BACKGROUND

Clonal Philadelphia (Ph)-negative cytogenetic abnormalities (CPCA) have been reported in chronic myeloid leukaemia (CML) patients treated with either interferon or tyrosine kinase inhibitor (TKI). However, the incidences and types of these cytogenetic abnormalities after treatment vary due to the limited populations enroled.

METHODS

We analysed the frequency and types of CPCA in a cohort of 607 CML patients in the chronic phase after TKI treatment. We also followed up these CPCA with a median of 31.8 months (range from 11 to 63 months) from diagnosis and investigated their effects on disease progression.

RESULTS

We found 18 out of 607 CML patients had cytogenetic abnormality in the Ph-negative cells with an incidence of 3%. In total, six types of chromosomal abnormalities have been identified in these 18 patients with the majority of them aneuploidy abnormalities, especially the trisomy 8. Four of 18 patients (22.2%) were noted to have several abnormalities in the Ph-negative cells. Furthermore, follow-up studies of these CPCA showed that they could be either persistent or transient (15 vs 3 patients), and may not affect disease progression since none of them developed transformed myelodysplasia or transformed acute myeloid leukaemia.

CONCLUSION

Three percent of CML patients in the chronic phase were observed to have CPCA during TKI treatment. Our results suggest that the detection of CPCA in CML may not predict disease progression.

Secondary clonal hematologic neoplasia following successful therapy for acute promyelocytic leukemia (APL): A report of two cases and review of the literature

Although rare, secondary clonal hematologic neoplasia may occur after successful therapy for acute promyelocytic leukemia (APL). These secondary clonal events may be considered therapy-related, but may also be due to an underlying background of clonal hematopoiesis from which both malignancies may develop. In this manuscript, we describe two patients with secondary clones after APL therapy characterized in one patient by deletion of chromosome 11q23 and, in the other, by monosomy of chromosome 7, and also provide a review of all secondary clonal disorders described after APL therapy. We suggest that since most reports identify karyotypic abnormalities not typically associated with chemotherapy, there may be another mechanism underlying secondary clonal development after complete response to initial APL therapy.

Diagnostic and prognostic cytogenetics of chronic myeloid leukaemia: an update

INTRODUCTION

Despite the advent of molecular assessment, banding cytogenetics and fluorescence in situ hybridization (FISH) still have a significant role in diagnostic and prognostic approaches to chronic myeloid leukaemia (CML). Area covered: At diagnosis and during treatment with tyrosine kinase inhibitors (TKIs), cytogenetics is used to detect the Philadelphia chromosome, with its typical translocation t(9;22)(q34;q11.2), and any additional or other chromosomal aberrations (ACAs and OCAs) that may arise in 5-10% of cases, the latter associated to transformation of the disease in blast phases. In this review, the potential role of banding cytogenetics and FISH is discussed through a review of published papers on the prognostic impact of these tools in CML treatment and monitoring. Expert commentary: Cytogenetic techniques, including banding cytogenetics and FISH, continue to maintain a crucial role in CML monitoring. At diagnosis and after 3 months of therapy, banding cytogenetics will continue to be an essential test to perform, but it will become redundant after the achievement of a major molecular response (MMR) assessed with molecular techniques. FISH analysis maintains its usefulness in monitoring the response to TKIs only in special situations.

Transient monosomy 7 in a chronic myelogenous leukemia patient during nilotinib therapy: a case report

Tyrosine kinase inhibitor treated chronic myelogenous leukemia patients with monosomy 7 arising in Philadelphia chromosome negative (Ph−) cells tend to evolve into MDS/AML. However, monosomy 7 in Ph− cells can be a transient finding, and it is not an absolute indication of the emergence of a new myeloid malignancy.

Molecular-defined clonal evolution in patients with chronic myeloid leukemia independent of the BCR-ABL status

To study clonal evolution in chronic myeloid leukemia (CML), we searched for BCR-ABL-independent gene mutations in both Philadelphia chromosome (Ph)-negative and Ph-positive clones in 29 chronic-phase CML patients by targeted deep sequencing of 25 genes frequently mutated in myeloid disorders. Ph-negative clones were analyzed in 14 patients who developed clonal cytogenetic abnormalities in Ph-negative cells during treatment with tyrosine kinase inhibitors (TKI). Mutations were detected in 6/14 patients (43%) affecting the genes DNMT3A, EZH2, RUNX1, TET2, TP53, U2AF1 and ZRSR2. In two patients, the mutations were also found in corresponding Ph-positive diagnostic samples. To further investigate Ph-positive clones, 15 randomly selected CML patients at diagnosis were analyzed. Somatic mutations additional to BCR-ABL were found in 5/15 patients (33%) affecting ASXL1, DNMT3A, RUNX1 and TET2. Analysis of individual hematopoietic colonies at diagnosis revealed that most mutations were part of the Ph-positive clone. In contrast, deep sequencing of subsequent samples during TKI treatment revealed one DNMT3A mutation in Ph-negative cells that was also present in Ph-positive cells at diagnosis, implying that the mutation preceded the BCR-ABL rearrangement. In summary, BCR-ABL-independent gene mutations were frequently found in Ph-negative and Ph-positive clones of CML patients and may be considered as important cofactors in the clonal evolution of CML.

Targeting developmental pathways in children with cancer: what price success?

Much of current cancer research is aimed at exploiting cancers' molecular addictions through targeted therapeutics, with notable successes documented in clinical trials. By their nature, these agents have different side-effect profiles than conventional chemotherapy drugs. Although few targeted agents have attained regulatory approval for use in children, paediatric oncologists are gaining experience with these drugs, which can have unique short-term and long-term effects in developing children that are unrecognised in adults. This Review summarises the rationale for targeted therapy, challenges in paediatric drug development, unique side-effect profiles of targeted agents, limited data from children treated with targeted agents, and implications of current knowledge and gaps therein. The demonstrated and potential effects of targeted therapies on normal tissue development and function are discussed. Future clinical trial design should include carefully considered assessment of the developmental effects of targeted therapy, and informed supportive-care recommendations.

The long-term clinical implications of clonal chromosomal abnormalities in newly diagnosed chronic phase chronic myeloid leukemia patients treated with imatinib mesylate

The aim of this study was to evaluate the long-term clinical significance of an additional chromosomal abnormality (ACA), variant Philadelphia chromosome (vPh) at diagnosis, and newly developed other chromosomal abnormalities (OCA) in patients with chronic myeloid leukemia (CML) on imatinib (IM) therapy. Sequential cytogenetic data from 281 consecutive new chronic phase CML patients were analyzed. With a median follow-up of 78.6 months, the 22 patients with vPh (P = 0.034) or ACA (P = 0.034) at diagnosis had more events of IM failure than did the patients with a standard Ph. The 5-year overall survival (OS), event-free survival (EFS), and failure-free survival (FFS) rates for patients with vPh at diagnosis were 77.8%, 75.0%, and 53.3%, respectively; for patients with ACA at diagnosis, 100%, 66.3%, and 52.1%, respectively; and for patients with a standard Ph, 96.0%, 91.3%, and 83.7%, respectively. During IM therapy, eight patients developed an OCA, which had no impact on outcomes as a time-dependent covariate in our Cox proportional hazards regression models. This study showed that vPh was associated with poor OS and FFS and that ACA had adverse effects on EFS and FFS. In addition, no OCA, except monosomy 7, had any prognostic impact, suggesting that the development of OCA may not require a change in treatment strategy.

Factors influencing a second myeloid malignancy in patients with Philadelphia-negative -7 or del(7q) clones during tyrosine kinase inhibitor therapy for chronic myeloid leukemia

The detection of Philadelphia-negative (Ph(neg)) cells with non-random karyotypic abnormalities after tyrosine kinase inhibitor (TKI) therapy of chronic myeloid leukaemia (CML) can be associated with myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML). To our knowledge, however, there have been no studies on variables influencing the risk of MDS/AML in patients with specific Ph(neg) karyotypes. We systematically examined studies reporting -7 or del(7q) within Ph(neg) cells in TKI-treated CML patients, and abstracted clinical and cytogenetic data from individual reports into a standardized format for further analysis. Of 53 patients, 43 had Ph(neg) -7 clones [as the sole abnormality (-7(sole)) in 29, or with other clones (-7(dual)) in 14], and del(7q) was present in 10. A total of 16/51 evaluable patients, all with -7, transformed to MDS/AML. Transformation was more frequent (15/16 patients) within 6 months of Ph(neg) -7 detection rather than subsequently (P < 0.0001). At first detection after TKI therapy, Ph(neg) abnormal clones comprised ≥50% of Ph(neg) cells in a greater proportion of patients with -7 than del(7q) (P = 0.035). Upon comparing -7(sole) and -7(dual), the latter was likely to be transient (P = 0.004), and AML was frequently observed with persistent -7 clones (P = 0.03). By logistic regression analysis (n = 36), clone size (P = 0.017), time-to-detection longer than 15 months (P = 0.02), and CML response (P = 0.085) were associated with MDS/AML. Validation of these novel associations in registry-based studies will help develop predictive criteria that define the MDS/AML risk in individual patients.

Evolution of T-cell clonality in a patient with Ph-negative acute lymphocytic leukemia occurring after interferon and imatinib therapy for Ph-positive chronic myeloid leukemia

Introduction

The development of Philadelphia chromosome (Ph) negative acute leukemia/myelodysplastic syndrome (MDS) in patients with Ph-positive chronic myeloid leukemia (CML) is very rare. The features of restrictive usage and absence of partial T cell clones have been found in patients with CML. However, the T-cell clonal evolution of Ph-negative malignancies during treatment for CML is still unknown.

Objective

To investigate the dynamic change of clonal proliferation of T cell receptor (TCR) Vα and Vβ subfamilies in one CML patient who developed Ph-negative acute lymphoblastic leukemia (ALL) after interferon and imatinib therapy.

Methods

The peripheral blood mononuclear cells (PBMC) samples were collected at the 3 time points (diagnosis of Ph-positive chronic phase (CP) CML, developing Ph-negative ALL and post inductive chemotherapy (CT) for Ph-negative ALL, respectively). The CDR3 size of TCR Vα and Vβ repertoire were detected by RT-PCR. The PCR products were further analyzed by genescan to identify T cell clonality.

Results

The CML patient who achieved complete cytogenetic remission (CCR) after 5 years of IFN-α therapy suddenly developed Ph-negative ALL 6 months following switch to imatinib therapy. The expression pattern and clonality of TCR Vα/Vβ T cells changed in different disease stages. The restrictive expression of Vα/Vβ subfamilies could be found in all three stages, and partial subfamily of T cells showed clonal proliferation. Additionally, there have been obvious differences in Vα/Vβ subfamily of T cells between the stages of Ph-positive CML-CP and Ph-negative ALL. The Vα10 and Vβ3 T cells evolved from oligoclonality to polyclonality, the Vβ13 T cells changed from bioclonality to polyclonality, when Ph-negative ALL developed.

Conclusions

Restrictive usage and clonal proliferation of different Vα/Vβ subfamily T cells between the stages of Ph-positive CP and Ph-negative ALL were detected in one patient. These changes may play a role in Ph- negative leukemogenesis.

Clonal hematopoiesis in Philadelphia chromosome-negative bone marrow cells of chronic myeloid leukemia patients receiving dasatinib

A clonal cytogenetic abnormality was observed in Philadelphia chromosome-negative bone marrow cells of 6/27 chronic myeloid leukemia patients (+8 in 4, -7 in 1, and 20q- in 1) with dasatinib-induced remissions. The X-linked human androgen receptor gene assay demonstrated clonality in one additional patient. Single nucleotide polymorphism array analysis revealed somatic uniparental disomy involving chromosome 17(p12-pter) in another patient. The TP53 gene had a 5' splice site deletion of exon 6 that caused alternative splicing, frame shifting and introduction of a premature stop codon. After three years, no patient developed myelodysplastic syndrome or acute myeloid leukemia.

Chronic myelogenous leukemia, BCR-ABL1+

Session 1 of the 2007 Workshop of the Society for Hematopathology/European Association for Haematopathology focused on chronic myelogenous leukemia, BCR-ABL1+ (CML). CML is a myeloproliferative neoplasm arising at the level of a pluripotent stem cell and consistently associated with the BCR-ABL1 fusion gene. CML most commonly manifests in a chronic phase of the disease with neutrophilic leukocytosis, and the demonstration of the Philadelphia chromosome is the ultimate confirmation of the diagnosis. However, in select cases, the initial diagnosis remains challenging, and a number of issues pertaining to the manifestations and disease evolution remain unresolved. These issues have been illustrated by the cases submitted to our workshop and include unusual manifestations of CML, including manifestation in the accelerated and/or blast phase, and patterns of disease progression and therapy resistance in the era of protein tyrosine kinase inhibitor therapy.

Clonal Cytogenetic Abnormalities in Philadelphia Chromosome Negative Cells in Chronic Myeloid Leukemia Patients Treated with Imatinib

Treatment of chronic myeloid leukemia (CML) with imatinib (Gleevec) induces a much higher rate of partial and complete cytogenetic responses (CCR) than interferon-alpha (IFN)-based therapies. Conventional wisdom suggests that elimination of the Philadelphia (Ph)- positive cells will lead to re-establishment of normal Ph-negative hematopoiesis. Surprisingly, karyotypic abnormalities were detected in the chromosome negative cells of some patients with cytogenetic response to imatinib. In some cases, this was associated with a myelodysplastic syndrome (MDS). While clonal evolution in Ph-positive cells is considered part of the progression of CML, clonal evolution in Ph-negative cells had been observed only rarely in a small number of patients treated with IFN or bone marrow transplantation, raising the question whether the phenomenon may be causally linked to imatinib therapy. In this manuscript, we will review the currently available data, suggest possible causes and discuss potential implications for patient management. We are fully aware that a systematic study of a larger patient cohort will be required to conclusively address these issues.

The prognosis for patients with chronic myeloid leukemia who have clonal cytogenetic abnormalities in philadelphia chromosome-negative cells

BACKGROUND

Clonal cytogenetic abnormalities (CCA) were detected in Philadelphia chromosome (Ph)-negative cells in some patients with chronic myeloid leukemia (CML) who attained a cytogenetic response to imatinib mesylate. In some patients, CCA/Ph-negative status was associated with myelodysplasia or acute myeloid leukemia. The objective of the current study was to determine the prognostic impact of CCA/Ph-negative cells.

METHODS

The authors compared the pretherapeutic risk factors (Kruskall-Wallis test), exposure to cytotoxic drugs (chi-square test), and overall and progression-free survival (Kaplan-Meyer and logistic regression analysis, respectively) of 515 patients with mostly chronic-phase CML who were treated with imatinib mesylate after failure of interferon-alpha according to whether they attained a major cytogenetic response (MCR) (n = 324 patients), an MCR with CCA/Ph-negative status (n = 30 patients), or no MCR (n = 161 patients).

RESULTS

CCA/Ph-negative status most frequently involved chromosomes Y, 8, and 7. No significant differences in pretherapeutic risk factors were detected between patients who attained an MCR with and without CCA/Ph-negative cells, except that exposure to alkylating agents was more frequent in patients with CCA/Ph-negative cells, and overall and progression-free survival were identical. With a median follow-up of 51 months, only 2 patients developed myelodysplastic syndromes (MDS).

CONCLUSIONS

The overall prognosis for patients who had CML with CCA/Ph-negative status was good and was driven by the CML response to imatinib mesylate. Isolated CCA/Ph-negative cells in the absence of morphologic evidence of MDS do not justify a change in therapy.

Chromosomal abnormalities in Philadelphia chromosome negative metaphases appearing during imatinib mesylate therapy in patients with newly diagnosed chronic myeloid leukemia in chronic phase

The development of chromosomal abnormalities (CAs) in the Philadelphia chromosome (Ph)-negative metaphases during imatinib (IM) therapy in patients with newly diagnosed chronic myecloid leukemia (CML) has been reported only anecdotally. We assessed the frequency and significance of this phenomenon among 258 patients with newly diagnosed CML in chronic phase receiving IM. After a median follow-up of 37 months, 21 (9%) patients developed 23 CAs in Ph-negative cells; excluding -Y, this incidence was 5%. Sixteen (70%) of all CAs were observed in 2 or more metaphases. The median time from start of IM to the appearance of CAs was 18 months. The most common CAs were -Y and + 8 in 9 and 3 patients, respectively. CAs were less frequent in young patients (P = .02) and those treated with high-dose IM (P = .03). In all but 3 patients, CAs were transient and disappeared after a median of 5 months. One patient developed acute myeloid leukemia (associated with - 7). At last follow-up, 3 patients died from transplantation-related complications, myocardial infarction, and progressive disease and 2 lost cytogenetic response. CAs occur in Ph-negative cells in a small percentage of patients with newly diagnosed CML treated with IM. In rare instances, these could reflect the emergence of a new malignant clone.

Acute myeloid leukemia developing during imatinib mesylate therapy for chronic myeloid leukemia in the absence of new cytogenetic abnormalities

The BCR/ABL tyrosine kinase inhibitor imatinib mesylate produces a high rate of cytogenetic responses in patients with Philadelphia (Ph)-positive chronic myeloid leukemia (CML), but secondary clonal chromosome abnormalities may develop in Ph-negative cells, and acute myeloid leukemia (AML) has been reported in patients with secondary chromosome abnormalities. We report a patient who developed AML during imatinib treatment of Ph-positive CML despite a cytogenetic response and absence of secondary chromosome abnormalities. Thus, development of AML as a rare event in CML patients with cytogenetic responses to imatinib therapy does not depend on the development of secondary cytogenetic abnormalities.

Management of Patients with Newly Diagnosed Chronic Myeloid Leukemia: Opportunities and Challenges

Chronic myelogenous leukemia (CML) is a progressive and often fatal hematopoietic neoplasm characterized by the presence of the Philadelphia chromosome. This arises from a balanced translocation between chromosomes 9 and 22, creating the bcr-abl fusion gene. It is often stated that the only proven curative option is allogeneic stem cell transplantation, which is indicated for only a limited subset of patients. The Bcr-Abl tyrosine kinase inhibitor imatinib represented a major advance over conventional CML therapy. After imatinib treatment, > 90% of patients had a complete hematologic response, and 70%-80% had a complete cytogenetic response. With 5 years of follow-up, the data are very encouraging and exhibit a major change in the natural history of the disease. The understanding of some of the mechanisms of resistance to imatinib has led to a rapid development of new agents that might overcome this resistance. The outlook today for patients with CML is much brighter than that of a few years ago.

Cytogenetic evolution patterns in CML post-SCT

The cytogenetic evolution patterns in chronic myeloid leukemia (CML) after allogeneic (allo) stem cell transplantation (SCT) are different from the ones observed in non-transplanted patients, a phenomenon suggested to be caused by the conditioning regime. We reviewed 131 CMLs displaying karyotypic evolution after SCT (122 allo, nine autologous (auto)), treated at Lund University Hospital or reported in the literature. Major route abnormalities (i.e., +8, +Ph, i(17q), +19, +21, +17 and -7) were seen in 14%, balanced aberrations in 61%, hyperdiploidy in 19%, pseudodiploidy in 79%, divergent clones in 14%, and Ph-negative clones in 21%. The breakpoints involved in secondary structural rearrangements clustered at 1q21, 1q32, 7q22, 9q34, 11q13, 11q23, 12q24, 13q14, 17q10 and 22q11. Cytogenetic abnormalities common in AML after genotoxic exposure, that is, der(1;7)(q10;p10), del(3p), -5, del(5q), -7, -17, der(17p), -18, and -21, were only rarely seen post-SCT. Comparing the cytogenetic features in relation to type of SCT revealed that balanced aberrations were significantly more common after allo than after auto SCT (64 and 22%, respectively, P=0.03). In addition, there was a trend as regards hyperdiploidy being more common after auto (P=0.07) and pseudodiploidy being more frequent after allo SCT (P=0.09). Possible reasons for these differences are discussed.

Rapid progression of Myelodysplastic syndrome to acute myeloid leukemia on sequential azathioprine, IFN-beta and copolymer-1 in a patient with multiple sclerosis

A woman with relapsing-remitting multiple sclerosis (MS) was treated with oral azathioprine (AZA) for 4 years and subsequently switched to interferon-beta1a. Five years later, leukopenia developed and resolved after interferon was discontinued; MS treatment was changed to copolymer-1. Recurrent pancytopenia subsequently led to diagnosis of myelodysplastic syndrome (MDS) with deletion of the long arm of chromosome 5 (MDS 5q-). Within several months, unusually rapid for this subtype, MDS progressed to secondary acute myeloid leukemia. While AZA is the probable cause for the chromosomal deletion and MDS, combined or sequential immunomodulatory therapies may permit clonal expansion of malignant hematopoietic progenitors.

Philadelphia-negative clonal hematopoiesis following imatinib therapy in patients with chronic myeloid leukemia: a report of nine cases and analysis of predictive factors

There are increasing reports of Philadelphia-negative (Ph-negative) clonal hematopoiesis developing among patients with chronic myeloid leukemia (CML) treated with imatinib mesylate (IM). To establish the incidence and significance of these chromosomal abnormalities, we analyzed data on 141 consecutive patients with CML treated with IM at the British Columbia Cancer Agency and Vancouver General Hospital from 1999 to 2004. The cumulative incidence of developing a Ph-negative clone three years from the start of IM was 8.7% at a median of 13.3 months. The Ph-negative clonal abnormalities included monosomy 7 and/or trisomy 8 (seven patients), monosomy for chromosomes X and 22 (one patient), and a (12;16) translocation (one patient). Two of the patients presented with the same chromosomal abnormality in both Ph-negative and Ph-positive cells. None of the Ph-negative clonal abnormalities was associated with myelodysplasia. In a multivariate analysis, an interval from diagnosis to initiation of IM of 1 year or less was associated with an increased risk of developing a Ph-negative clone (relative risk = 20.2; P = 0.025). There was no difference, however, in event-free survival between patients who did and did not develop Ph-negative clones. Therefore, while the development of Ph-negative clonal hematopoiesis in patients with CML treated with IM is uncommon, it appears to be more frequent than that previously seen with IFN, but it does not seem to confer a worse prognosis.

Chronic myeloid leukemia: diagnosis and treatment

Chronic myeloid leukemia (CML) has become a model in research and management among malignant disorders. Since the discovery of the presence of a unique and constant chromosomal abnormality slightly more than 40 years ago, substantial progress has been made in the understanding of the biology of the disease. This progress has translated into significant improvement in the longterm prognosis of patients with this disease. This change came first with the use of stem cell transplantation and interferon alfa, but recently it has opened the era of molecularly targeted therapies. Imatinib, a potent and selective tyrosine kinase inhibitor, may be the best example of our attempts to identify molecular abnormalities and develop drugs directed specifically at them. Furthermore, the understanding of at least some of the mechanisms of resistance to imatinib has led to rapid development of new agents that may overcome this resistance. The outlook today for patients with CML is much brighter than just a few years ago. It is our hope that this fascinating journey in CML can be replicated in other malignancies. In this article, we review our current understanding of this disease.

Myelodysplastic syndromes and acute leukemia developing after imatinib mesylate therapy for chronic myeloid leukemia

During therapy with imatinib, some patients with chronic myeloid leukemia (CML) develop chromosomal abnormalities in Philadelphia chromosome (Ph)-negative cells. These abnormalities are frequently transient and their clinical consequence is unclear. Although some reports have suggested that the abnormalities might be associated with secondary myelodysplastic syndrome (MDS), the diagnosis has not always been established using standard criteria. We report 3 cases of patients treated with imatinib for CML who were subsequently found to have chromosomal abnormalities in Ph-negative cells. One of them developed acute myelogenous leukemia (AML) and the other 2 developed high-risk MDS that rapidly transformed to AML. These cases were identified in a total study group of 1701 patients. Although these occurrences are rare, the findings highlight the need for close monitoring of patients with CML treated with imatinib.

Limited clinical value of regular bone marrow cytogenetic analysis in imatinib-treated chronic phase CML patients monitored by RQ-PCR for BCR-ABL

Real-time quantitative polymerase chain reaction (PCR) for BCR-ABL mRNA in the peripheral blood (RQ-PCR) provides an accurate and reliable measure of response to therapy in chronic myeloid leukaemia (CML). We wanted to determine in what circumstances additional clinically relevant information was provided by simultaneous cytogenetic analysis in RQ-PCR monitored patients receiving imatinib treatment. We analysed 828 simultaneous RQ-PCR and bone marrow cytogenetic analyses from 183 patients with chronic phase CML with a median follow-up of 20 months. Cytogenetic progression was defined as Philadelphia (Ph)-positive clonal evolution, loss of complete cytogenetic response or an increase of > or = 20% Ph-positive cells. Cytogenetic progression occurred in 24/183 (13%) patients. At the time of cytogenetic progression, none of the 24 patients had a major molecular response (MMR; > or = 3-log reduction in BCR-ABL from standardised baseline). There were 320 RQ-PCR results from 95 patients indicating MMR. No abnormality was detected in any of the corresponding cytogenetic analyses. A policy of regular RQ-PCR monitoring with cytogenetic analysis targetted only to patients who have not achieved, or have lost MMR would represent a rational approach to monitoring and spare most patients the discomfort of multiple marrow aspirates. This approach depends upon availability of an accurate, reproducible RQ-PCR assay with ongoing quality assurance.

Clonal evolution in chronic myelogenous leukemia

Clonal evolution (CE) may be a marker of disease progression in chronic myelogenous leukemia (CML) and is thought to reflect the genetic instability of the highly proliferative CML progenitors. The frequency of CE increases with advancing stage, rising from 30%in accelerated phase and up to 80% in blast crisis. Given its association with disease progression, CE is considered a feature that defines accelerated-phase CML; however, not all studies have demonstrated a uniformly poor outcome for patients with CE. Chromosomal abnormalities in Ph chromosome negative metaphases increasingly have been recognized in patients treated with imatinib. The true incidence of this phenomenon is not clear but appears to occur in 2% to 17% of imatinib-treated patients. Regardless of the precise mechanism and the long-term clinical implications, the findings described in this article underscore the importance of routine cytogenetic analysis for patients treated with imatinib. The continued study of these phenomena will help us to understand better the pathogenesis of CML and improve the long-term treatment of patients with CML.

Report of 34 patients with clonal chromosomal abnormalities in Philadelphia-negative cells during imatinib treatment of Philadelphia-positive chronic myeloid leukemia

Imatinib mesylate (Gleevec), an inhibitor of the BCR-ABL tyrosine kinase, was introduced recently into the therapy of chronic myeloid leukemia (CML). Several cases of emergence of clonal chromosomal abnormalities after therapy with imatinib have been reported, but their incidence, etiology and prognosis remain to be clarified. We report here a large series of 34 CML patients treated with imatinib who developed Philadelphia (Ph)-negative clones. Among 1001 patients with Ph-positive CML treated with imatinib, 34 (3.4%) developed clonal chromosomal abnormalities in Ph-negative cells. Three patients were treated with imatinib up-front. The most common cytogenetic abnormalities were trisomy 8 and monosomy 7 in twelve and seven patients, respectively. In 15 patients, fluorescent in situ hybridization with specific probes was performed in materials archived before the initiation of imatinib. The Ph-negative clone was related to previous therapy in three patients, and represented a minor pre-existing clone that expanded after the eradication of Ph-positive cells with imatinib in two others. However, in 11 patients, the new clonal chromosomal abnormalities were not detected and imatinib may have had a direct effect. No myelodysplasia was found in our cohort. With a median follow-up of 24 months, one patient showed CML acceleration and two relapsed.

Effect of interferon-α on chromosome abnormalities in treated chronic myelogenous leukemia patients

To investigate the relationship of chromosomal aberrations at blastic crisis (BC) in chronic myelogenous leukemia (CML), with previous therapies and with atomic bomb (AB) exposure, we studied 114 CML patients who developed BC, including 23 AB survivors in Hiroshima. In total, only 45.6% showed major-route abnormalities, which figure was far lower than those previously reported, implying possibility of geographical difference. Occurrence of major-route abnormality was not associated with either duration of chronic phase or survival time after BC. Patients treated with interferon-alpha (IFNalpha) showed lower frequency of major-route abnormalities and lower number of abnormal chromosomes than did patients treated with busulfan (Bu). The frequency of trisomy 8 was lower and monosomy 7 was higher in IFNalpha-treated than in Bu-treated patients. The frequency of unusual abnormalities at BC in IFNalpha-treated patients was indistinguishable from those in Bu-treated patients and, notably, a more common (40%) feature in IFNalpha-treated patients was no change in the cytogenetic picture. Thus, we conclude that IFNalpha action on chromosome aberration is basically quite neutral and that IFNalpha does not induce any specific aberrations, including unusual ones at BC, with an exception of deletion of chromosome 7. Atomic bomb exposure status did not make any difference in secondary abnormalities at BC.

Chromosomal abnormalities in Philadelphia chromosome-negative metaphases appearing during imatinib mesylate therapy in patients with Philadelphia chromosome-positive chronic myelogenous leukemia in chronic phase

BACKGROUND

Anecdotal cases of chromosomal abnormalities in Philadelphia chromosome (Ph)-negative metaphases have been reported in patients with chronic myelogenous leukemia (CML) in the chronic phase during treatment with interferon and, more recently, with imatinib. This phenomenon is different from true clonal evolution in that the additional cytogenetic abnormality occurs in Ph-negative cells.

METHODS

The authors analyzed their experience with 342 patients with CML in chronic phase treated with imatinib to investigate the frequency and significance of this event.

RESULTS

After a median follow-up of 30 months (range, 16-35 months), 21 patients (6%; 95% confidence interval, 0.04, 0.09) developed 25 chromosomal abnormalities in Ph-negative cells. Thirteen (54%) of these abnormalities were seen in 2 or more metaphases. The median time from the start of treatment with imatinib to the appearance of the abnormalities was 6 months (range, 3-22 months). The most common cytogenetic abnormality detected was trisomy 8 (33%). Twenty of 21 patients (95%) achieved a major (Ph < 35%) cytogenetic response (complete cytogenetic response in 13-62%). After a median follow-up of 22 months (range, 4-33 months), all 21 patients were alive, 20 of them in chronic phase and in complete hematologic response. None of the patients showed features of myelodysplasia.

CONCLUSIONS

Cytogenetic abnormalities occur in Ph-negative cells in a fraction of patients with CML in chronic phase treated with imatinib. With a short follow-up, no clear clinical consequences can be identified.

Acute lymphoblastic leukemia without the Philadelphia chromosome occurring in chronic myelogenous leukemia with the Philadelphia chromosome

The blast crisis in chronic myelogenous leukemia (CML) is related to the evolution of a Philadelphia chromosome (Ph)-positive clone. Secondary chromosomal abnormalities accompanied by t(9;22) are found in 70-80% of blast crises. Here we describe a patient with Ph-positive CML, who developed Ph-negative acute lymphoblastic leukemia (ALL). A 52-year-old man was diagnosed with CML with the Ph chromosome in the chronic phase. He achieved a partial cytogenetic response after 4 months of imatinib mesylate therapy. After 8 months, common ALL occurred. At that time his karyotype was normal and the Ph chromosome was not noted.

The emergence of Ph-, trisomy -8+ cells in patients with chronic myeloid leukemia treated with imatinib mesylate

OBJECTIVE

To describe clinical and laboratory features of a cohort of patients with chronic myelogenous leukemia (CML) who developed Ph(-), trisomy 8(+) metaphases while on treatment with imatinib mesylate.

PATIENTS AND METHODS

Conventional cytogenetics and triple-color interphase fluorescence in situ hybridization were used to identify 5 of 310 studied patients who, on follow-up analysis, had Ph(-), trisomy 8(+) cells while on therapy.

RESULTS

None of the 5 patients had cytogenetic evidence of clonal evolution at the start of treatment with imatinib. All patients developed grade 3 or 4 neutropenia and thrombocytopenia during treatment. The emergence of Ph(-), trisomy 8(+) metaphases was seen at 3, 6, 13, 16, and 18 months from the start of treatment and was present at multiple time points. The maximum number of trisomy 8 metaphases ranged from 25 to 50%. Concomitantly, all patients had a profound suppression of Ph(+) cells (ranging from 0 to 65%) as well as the appearance of normal metaphases, ranging from 6 to 55%. None of the patients has shown clinical or hematologic signs of progression to a more advanced phase of CML.

CONCLUSIONS

While on treatment with imatinib mesylate a small group (less than 5%) of patients with CML developed Ph(-) trisomy 8(+) clone associated with pancytopenia. None of the patients developed clinical or hematological signs of progression to a more advanced phase of CML. These observations suggest that identification of trisomy 8 cells may represent clonal Ph(-) cells that were uncovered by treatment with a selective and potent inhibitor of Ph(+) cells.

The occurrence of Philadelphia chromosome (Ph) negative leukemia after hematopoietic stem cell transplantation for Ph positive chronic myeloid leukemia: implications for disease monitoring and treatment

Chronic myeloid leukemia (CML) is a clonal neoplastic disorder, characterized by t(9;22)(q34;q11) that results in the formation of the Philadelphia chromosome (Ph) and the BCR/ABL fusion gene. Allogeneic hematopoietic stem cell transplantation (HSCT) is a curative treatment for CML. Much of its therapeutic efficacy is attributed to a graft-versus-leukemia (GVL) effect exerted by donor-derived lymphoid cells against the Ph positive (Ph+) clone. Post-HSCT monitoring by cytogenetic and molecular detection of the Ph+ clone is necessary, so that pre-emptive immunologic or pharmacologic treatment may be administered at an early stage of relapse. However, under rare circumstances a second Ph negative (Ph-) leukemia may evolve post-HSCT. The pathogenetic possibilities included leukemia arising from donor-derived hematopoietic stem cells (HSCs), or transformation of residual recipient-derived Ph- HSCs that have survived the conditioning chemotherapy and radiotherapy. Recipient-derived Ph- leukemia may be related to genetic alterations that precede the onset of CML, or myelotoxic effects of the HSCT conditioning regimen. The diagnosis of Ph- relapses requires detailed investigations by conventional karyotyping, fluorescence in-situ hybridization (FISH), and molecular analysis; as well as chimerism studies that help to document the donor or recipient origin of the leukemia. Although uncommonly reported in the past, Ph- relapses may in fact be more frequent if leukemic relapses post-HSCT are more thoroughly evaluated with these investigations. The recognition of Ph- relapses are important in several ways. Ph- relapses cannot be identified by monitoring investigations targeting the Ph+ clone, so that the early detection of Ph- leukemia is usually not possible. Furthermore, Ph- relapses will not respond to therapeutic strategies effective against the Ph+ CML clone.

Prognostic significance of cytogenetic clonal evolution in patients with chronic myelogenous leukemia on imatinib mesylate therapy

Cytogenetic clonal evolution (CE) is a known poor prognostic factor in Philadelphia chromosome-positive chronic myelogenous leukemia (Ph-positive CML). However, its prognostic relevance in the era of imatinib therapy is unknown. We investigated the independent prognostic relevance of CE in 498 patients with Ph-positive CML treated with imatinib for chronic or accelerated phases. One hundred twenty-one patients had CE alone (n = 70) or with other accelerated phase criteria (n = 51). Patients were compared in 4 categories: chronic phase (n = 295), CE only (n = 70), accelerated phase without CE (n = 82), and accelerated phase with CE (n = 51). Statistical methods used established methodologies for univariate and multivariate analyses. In chronic and accelerated phases of CML, CE was not associated with significant differences in major or complete cytogenetic response rates, but it was an independent poor prognostic factor for survival by multivariate analyses in both chronic (P =.005) and accelerated phase (P =.03). Multivariate analyses conducted at the 3-month landmark (including the 3-month cytogenetic response) identified the lack of cytogenetic response at 3 months to be a stronger independent poor prognostic factor for survival than CE for both chronic (major cytogenetic response versus other) and accelerated phase (any cytogenetic response versus other). We conclude that cytogenetic CE is not an important factor for achieving major or complete cytogenetic response with imatinib mesylate therapy, but it is an independent poor prognostic factor for survival in both chronic and accelerated phases of CML. The 3-month cytogenetic response to imatinib mesylate refined the prognostic relevance of such studies in patients on imatinib mesylate therapy.

Cytogenetic studies in patients on imatinib

With the introduction of imatinib (Gleevec) (formerly STI571) for the treatment of chronic myeloid leukemia (CML), the various diagnostic methods used to monitor patients must be re-evaluated. Conventional cytogenetics has been the established method for follow-up of patients treated with interferon-alpha (IFN-alpha), and the prognostic value of major and complete cytogenetic remission was demonstrated in a number of studies. In patients on imatinib, these endpoints will likely remain valid, although longer observation is required. Cytogenetic remission as a time-dependent variable may aid risk stratification early on. Clonal evolution, ie, the presence of cytogenetic abnormalities in addition to the Philadelphia (Ph) chromosome, may provide important prognostic information as to the likely response to imatinib in all phases of CML but must be interpreted within the context of other disease characteristics. In some patients, clonal evolution is related to imatinib resistance. Information regarding the impact of specific types of additional cytogenetic abnormalities is still limited. Surprisingly, nonrandom karyotypic abnormalities have also been noted in the Ph-negative cells of some patients in cytogenetic remission. This is a novel phenomenon whose causality and prognostic implications require thorough and systematic evaluation.

Ph-negative acute lymphocytic leukemia occurring after interferon therapy for Ph-positive chronic myelocytic leukemia

We report a unique case of chronic myelocytic leukemia (CML) with the Philadelphia (Ph) chromosome. The patient obtained cytogenetic complete remission (CR) after treatment with interferon (IFN). When he transformed to acute lymphocytic leukemia (ALL), cytogenetic analysis showed that the karyotype was normal and fluorescence in situ hybridization (FISH) indicated that blast cells were Ph-negative. Immunophenotyping showed that the cells were CD34-positive and CD38-negative. Blast cells in his final stage were BCR/ABL rearrangement negative by reverse transcription polymerase chain reaction (RT-PCR).

Emergence of clonal cytogenetic abnormalities in Ph- cells in some CML patients in cytogenetic remission to imatinib but restoration of polyclonal hematopoiesis in the majority

Chronic myelogenous leukemia (CML) is characterized by the presence of a Bcr-Abl fusion protein with deregulated tyrosine kinase activity that is required for maintaining the malignant phenotype. Imatinib, a selective inhibitor of Bcr-Abl, induces major cytogenetic remission (MCR) or complete cytogenetic remission (CCR) in the majority of patients with CML in first chronic phase. However, thorough re-evaluation of cytogenetics in a cohort of patients in MCR or CCR demonstrated clonal karyotypic abnormalities in more than 10% of cases, some of which were clinically associated with a myelodysplastic syndrome (MDS). Further analysis identified previous exposure to cytarabine and idarubicin as significant risk factors for the subsequent occurrence of abnormalities in Philadelphia chromosome-negative (Ph-) cells. To investigate if cytogenetically normal but clonal hematopoiesis might be present in other patients in cytogenetic remission, we studied X-chromosome inactivation as a marker of clonality by polymerase chain reaction analysis of the human androgen receptor (HUMARA). We find that imatinib restores a polyclonal pattern in most patients in CCR and MCR. Nonetheless, our results are consistent with the notion that targeted therapy of CML with imatinib favors the manifestation of Ph- clonal disorders in some patients. They indicate that patients on imatinib should be followed with conventional cytogenetics, even after induction of CCR.

Demonstration of Philadelphia chromosome negative abnormal clones in patients with chronic myelogenous leukemia during major cytogenetic responses induced by imatinib mesylate

Imatinib mesylate, an Abl-specific kinase inhibitor, produces sustained complete hematologic responses (CHR) and major cytogenetic responses (MCR) in chronic myeloid leukemia (CML) patients, but long-term outcomes in these patients are not yet known. This article reports the identification of clonal abnormalities in cells lacking detectable Philadelphia (Ph) chromosome/BCR-ABL rearrangements from seven patients with chronic- or accelerated-phase CML, who were treated with imatinib. All seven patients were refractory or intolerant to interferon therapy. Six of seven patients demonstrated MCR and one patient, who had a cryptic translocation, achieved low-level positivity (2.5%) for BCR-ABL by fluorescence in situ hybridization. The median duration of imatinib treatment before the identification of cytogenetic abnormalities in BCR-ABL-negative cells was 13 months. The most common cytogenetic abnormality was trisomy 8, documented in three patients. All patients had varying degrees of dysplastic morphologic abnormalities. One patient exhibited increased numbers of marrow blasts, yet consistently demonstrated no Ph-positive metaphases and the absence of morphologic features of CML. The presence of clonal abnormalities in Ph-negative cells of imatinib-treated CML patients with MCR and CHR highlights the importance of routine metaphase cytogenetic testing and long-term follow-up of all imatinib-treated patients.

Coexistence of independent myelodysplastic and Philadelphia chromosome positive clones in a patient treated with hydroxyurea

We report a patient with Philadelphia chromosome positive (Ph +ve) chronic myelogenous leukemia (CML), treated with hydroxyurea alone, who upon disease progression developed an additional Ph - ve clone containing chromosomal abnormalities typical of myelodysplastic syndrome (MDS). Retrospective analysis of a cryopreserved stem cell specimen from diagnosis confirmed that this second clone developed during the course of treatment. The development of a clone with additional cytogenetic abnormalities in CML has only been reported after leukemogenic treatment, stem cell transplantation or interferon. We report a case of secondary Ph - ve MDS/AML during blast crisis in a patient treated with hydroxyurea for CML.

Trisomy 8 in myelodysplasia and acute leukemia is constitutional in 15-20% of cases

The trisomy 8 found in malignancies may derive from a constitutional trisomy 8 mosaicism (CT8M), and in these cases the trisomy itself may be regarded as the first mutation in a multistep carcinogenetic process. To assess the frequency of CT8M in hematological dysplastic and neoplastic disorders with trisomy 8, an informative sample of 14 patients was collected. The data ascertained included chromosome analyses of fibroblast cultures and of PHA-stimulated blood cultures in patients with normal blood differential count, as well as possible CT8M clinical signs. One patient showed trisomy 8 in all cell types analyzed and undoubtedly has a CT8M; a second patient consistently showed trisomy 8 in PHA-stimulated blood cultures when no immature myeloid cells were present in blood and should be considered as having CT8M; a third patient, with Philadelphia-positive chronic myelocytic leukemia, was more difficult to interpret, but the possibility that she had CT8M is likely. A few clinical signs of CT8M were also present in these three patients. Our data indicate that the frequency of CT8M in hematological dysplastic and neoplastic disorders with trisomy 8 is approximately 15-20%.

Cytogenetics of chronic myeloid leukaemia

The standard Philadelphia (Ph) translocation t(9;22), its variants and a proportion of Ph-negative cases are positive for the BCR-ABL fusion gene, as determined by molecular analysis. Extensive deletions of chromosome 9 and 22 derived sequences around the translocation breakpoints on the derivative 9 are seen in 10-30% of patients at diagnosis and may confer a worse prognosis. Additional cytogenetic changes can occur in the few months before or during disease progression and are often specific for blast morphology; however, the molecular basis of the most common additional cytogenetic abnormalities is largely unknown. Cytogenetics is important for monitoring patient response to treatment but is increasingly being replaced by the more sensitive and less invasive techniques of RT-PCR and FISH.