Balanced chromosome abnormalities inv(16) and t(15;17) in therapy-related myelodysplastic syndromes and acute leukemia: report from an international workshop

Evidence for direct involvement of epirubicin in the formation of chromosomal translocations in t(15;17) therapy-related acute promyelocytic leukemia

Therapy-related acute promyelocytic leukemia (t-APL) with t(15;17)(q22;q21) involving the PML and RARA genes is associated with exposure to agents targeting topoisomerase II (topoII), particularly mitoxantrone and epirubicin. We previously have shown that mitoxantrone preferentially induces topoII-mediated DNA damage in a "hotspot region" within PML intron 6. To investigate mechanisms underlying epirubicin-associated t-APL, t(15;17) genomic breakpoints were characterized in 6 cases with prior breast cancer. Significant breakpoint clustering was observed in PML and RARA loci (P = .009 and P = .017, respectively), with PML breakpoints lying outside the mitoxantrone-associated hotspot region. Recurrent breakpoints identified in the PML and RARA loci in epirubicin-related t-APL were shown to be preferential sites of topoII-induced DNA damage, enhanced by epirubicin. Although site preferences for DNA damage differed between mitoxantrone and epirubicin, the observation that particular regions of the PML and RARA loci are susceptible to these agents may underlie their respective propensities to induce t-APL.

Therapy-related myeloid neoplasms

Session 5 of 2007 Workshop of the Society for Hematopathology/European Association for Haematopathology focused on therapy-related myeloid neoplasms. This report discusses the diversity and relevance of clinical, pathologic, and genetic features and provides an update on the pathogenesis of these disorders. We highlight common diagnostic issues such as the differentiation between therapy-related myelodysplastic syndrome and therapy-related acute erythroid leukemia. As similar therapeutic interventions are frequently considered for patients with either of these diagnoses, in the current World Health Organization classification, regardless of morphologic presentation, therapy-related myeloid neoplasms are considered together as a unique clinicopathologic syndrome of therapy-related myelodysplastic syndrome/acute myeloid leukemia. Nevertheless, recognition of the diverse morphologic features is crucial as bone marrow morphologic examination remains the first and important step of patient evaluation. We also present examples of therapy-related acute myeloid leukemias with recurrent cytogenetic abnormalities. In these cases, the precise classification is clinically important because it is associated with distinct clinical outcome.

Survival is poorer in patients with secondary core-binding factor acute myelogenous leukemia compared with de novo core-binding factor leukemia

BACKGROUND

Therapy related secondary acute myelogenous leukemia (AML) was commonly associated with prior exposure to alkylating agents or topoisomerase inhibitor. The long-term outcome of such patients with secondary AML was found to be worse than that of patients with de novo AML. Earlier reports suggested similar outcomes for patients with de novo and secondary AML associated with core-binding factor (CBF) abnormalities.

METHODS

A total of 188 patients with CBF AML were analyzed. The frequency of secondary CBF AML was 9%.

RESULTS

Patients with secondary CBF AML were found to have significantly worse overall (OS) and event-free survival (EFS) compared with patients with de novo CBF AML. Secondary CBF AML status appeared to have only marginal significance in multivariate analysis.

CONCLUSIONS

Matched analysis (by age, Eastern Cooperative Oncology Group performance status, and additional cytogenetic abnormality) indicated worse OS and EFS in patients with secondary CBF AML.

Mitoxantrone-Associated Acute Myelogenous Leukemia in a Patient with High-Risk Adenocarcinoma of the Prostate: A Case Report and Brief Review

BACKGROUND

Mitoxantrone, a topoisomerase II-targeted drug, is used to treat several conditions and is a Food and Drug Administration approved chemotherapeutic agent for the treatment of advanced carcinoma of the prostate.

CASE REPORT

A 64-year-old male with high-risk prostate cancer was treated with adjuvant mitoxantrone (12 mg/meter2) every 3 weeks for 6 cycles. Approximately 10 months after finishing therapy, he was diagnosed with an inv [16] Acute Myelogenous Leukemia (AML). Despite aggressive treatment and support, the patient had a rapidly fatal clinical course.

CONCLUSION

Despite its regular use in this setting, this is the first reported case of treatment-associated AML after mitoxantrone in prostate cancer.

The 2008 revision of the World Health Organization (WHO) classification of myeloid neoplasms and acute leukemia: rationale and important changes

Recently the World Health Organization (WHO), in collaboration with the European Association for Haematopathology and the Society for Hematopathology, published a revised and updated edition of the WHO Classification of Tumors of the Hematopoietic and Lymphoid Tissues. The 4th edition of the WHO classification incorporates new information that has emerged from scientific and clinical studies in the interval since the publication of the 3rd edition in 2001, and includes new criteria for the recognition of some previously described neoplasms as well as clarification and refinement of the defining criteria for others. It also adds entities-some defined principally by genetic features-that have only recently been characterized. In this paper, the classification of myeloid neoplasms and acute leukemia is highlighted with the aim of familiarizing hematologists, clinical scientists, and hematopathologists not only with the major changes in the classification but also with the rationale for those changes.

Management of acute promyelocytic leukemia: recommendations from an expert panel on behalf of the European LeukemiaNet

The introduction of all-trans retinoic acid (ATRA) and, more recently, arsenic trioxide (ATO) into the therapy of acute promyelocytic leukemia (APL) has revolutionized the management and outcome of this disease. Several treatment strategies using these agents, usually in combination with chemotherapy, but also without or with minimal use of cytotoxic agents, have provided excellent therapeutic results. Cure of APL patients, however, is also dependent on peculiar aspects related to the management and supportive measures that are crucial to counteract life-threatening complications associated with the disease biology and molecularly targeted treatment. The European LeukemiaNet recently appointed an international panel of experts to develop evidence- and expert opinion-based guidelines on the diagnosis and management of APL. Together with providing current indications on genetic diagnosis, modern risk-adapted front-line therapy and salvage treatment, the review contains specific recommendations for the identification and management of most important complications such as the bleeding disorder, APL differentiation syndrome, QT prolongation and other ATRA- and ATO-related toxicities, as well as for molecular assessment of response to treatment. Finally, the approach to special situations is also discussed, including management of APL in children, elderly patients, and pregnant women.

Therapy-related myeloid leukemia

Therapy-related myelodysplastic syndrome and acute myeloid leukemia (t-MDS/t-AML) are thought to be the direct consequence of mutational events induced by chemotherapy, radiation therapy, immunosuppressive therapy, or a combination of these modalities, given for a pre-existing condition. The outcomes for these patients have been poor historically compared to people who develop de novo AML. The spectrum of cytogenetic abnormalities in t-AML is similar to de novo AML, but the frequency of unfavorable cytogenetics, such as a complex karyotype or deletion or loss of chromosomes 5 and/or 7, is considerably higher in t-AML. Survival varies according to cytogenetic risk group in t-AML patients, with better outcomes being observed in those with favorable-risk karyotypes. Treatment recommendations should be based on performance status and karyotype. A deeper understanding of the factors that predispose patients to the development of therapy-related myeloid leukemia would help clinicians monitor patients more carefully after treatment for a primary condition. Ultimately, this knowledge could influence initial treatment strategies with the goal of decreasing the incidence of this serious complication.

[A case of therapy-related acute myeloid leukemia associated with inv(16)]

The inv(16)(p13q22) is found in de novo AML and is closely associated with the FAB subtype M4eo. The inv(16) is rarely reported in therapy-related AML (t-AML) patients. Herein, we report a case of t-AML with inv(16) after combination chemotherapy using antimitotic agent and alkylating agent (cis-platin-paclitaxel) for ovarian serous cystadenocarcinoma.

Predictors of outcome following myeloablative allo-SCT for therapy-related myelodysplastic syndrome and AML

Administration of alkylating agents (Alk), topoisomerase II inhibitors (Topo II) and radiotherapy (RT) can result in therapy-related myelodysplastic syndrome or acute myelogenous leukaemia (t-MDS/t-AML), the optimal treatment for which is allo-SCT. A retrospective review was performed of 24 patients who underwent related- or unrelated-donor SCT for t-MDS/t-AML at our institution. Eight patients remain alive and in continuous remission (median follow-up 54 months (range, 12-161)) with estimated 5-year EFS being 30% (95% confidence intervals 16-58%). Corresponding actuarial risks of relapse and non-relapse mortality (NRM) are 39% (19-60%) and 30% (13-50%), respectively. EFS was 40% in Alk/RT-related t-MDS/t-AML and 11% in Topo II-related t-MDS/t-AML (P=0.05), with an increased risk of relapse in the latter (56 vs 29%, respectively (P=0.05)). In multivariate analysis, development of acute GVHD (P=0.009) and Topo II-related t-MDS/t-AML (P=0.018) were associated with inferior EFS. Patients with acute GVHD had an increased risk of NRM (P=0.03) whereas risk of relapse was higher for patients of advanced age (P=0.046) and for patients who underwent bone marrow (vs blood) SCT (P=0.032). Allo-SCT can result in long-term survival for individuals with t-MDS/t-AML although outcome in Topo II-related t-MDS/t-AML patients remains suboptimal.

Spectral karyotyping and fluorescence in situ hybridization analyses identified a novel three-way translocation involving inversion 16 in therapy-related acute myeloid leukemia M4eo

We report a novel three-way translocation involving inversion 16 and chromosome 12 at bands 16p13, 16q22, and 12q24 in a patient with therapy-related acute myeloid leukemia (AML)-M4eo. Conventional G-banding of bone marrow cells at diagnosis was suggestive of inv(16)(p13q22) and a translocation of chromosomes 12 and 16. The presence of inv(16) was confirmed by reverse-transcription polymerase chain reaction (RT-PCR) analysis, which corresponded to the type A CBFB-MYH11 chimeric transcript. Spectral karyotyping (SKY) analysis clearly identified a reciprocal translocation between chromosomes 12 and 16. In addition, dual-color fluorescence in situ hybridization (FISH) analysis revealed a fusion signal for the CBFB and MYH11 probes and a signal for the MYH11 probe on the der(16) chromosome, as well as a signal for the CBFB probe on the der(12) chromosome. Thus, the karyotype was refined to 46,XX,der(12)t(12;16)(q24;q22),der(16)inv(16)(p13q22)t(12;16). Although we could not establish that this complex chromosomal aberration occurred either as a one-step, three-way event, or a sequential event with inv(16)(p13q22) followed by t(12;16)(q24;q22), SKY in combination with FISH and RT-PCR analyses successfully detected this complex chromosome abnormality in the patient.

Outcome of patients who develop acute leukemia or myelodysplasia as a second malignancy after solid tumors treated surgically or with strategies that include chemotherapy and/or radiation

BACKGROUND

Evaluation of therapeutic outcomes and risk factors was undertaken for patients with primary solid tumors (PST) developing acute leukemia or myelodysplasia (MDS) as a second malignancy.

METHODS

In all, 131 consecutive patients presenting to a single institution with leukemia or MDS after treatment for PST with surgery or chemotherapy/radiotherapy were examined. Management of the secondary acute leukemia and MDS consisted either of intensive therapy including allogeneic blood and marrow transplants or supportive measures.

RESULTS

The time from diagnosis of PST to development of acute leukemia or MDS, the cytogenetic profile of patients, and their survival were similar irrespective of PST therapy with surgery alone or strategies involving chemotherapy and/or radiation. The median survival of all 131 patients was 10.5 months with a 5-year survival of 15.6%. Induction therapy and/or transplantation resulted in a median survival of 13.6 months and a 5-year survival of 26.6% compared with 6.5 months and 2% with supportive measures. Subset analysis of transplant recipients revealed a median survival of 17.6 months and a 37.9% 5-year survival. Despite a significantly lower recurrence rate the survival of transplant recipients was not improved secondary to a higher treatment-related mortality (TRM) rate.

CONCLUSIONS

Patients developing acute leukemia or MDS after PST demonstrated similar cytogenetic profiles and clinical outcomes independent of the type of treatment. Survival was significantly better for patients able to undergo intensive therapy compared with supportive measures. The low recurrence rate for allograft recipients was consistent with a potent antileukemic effect that may translate into a survival benefit if TRM could be reduced.

Randomization reveals unexpected acute leukemias in Southwest Oncology Group prostate cancer trial

PURPOSE

Southwest Oncology Group (SWOG) study 9921 is a randomized, phase III, intergroup study to define the role of adjuvant chemotherapy in patients with high-risk prostate cancer.

PATIENTS AND METHODS

We allocated 983 patients with prostate cancer with high-risk features to receive 2 years of androgen-deprivation therapy (ADT) with or without six cycles of mitoxantrone (12 mg/m(2)) after prostatectomy.

RESULTS

In January 2007, SWOG 9921 was closed to further accrual after three cases of acute myelogenous leukemia (AML) were reported of a total of 487 patients in the mitoxantrone treatment arm. The key cytogenetic features of these cases included inv(16) in the first case, t(15;17) in the second, and del(5) in the third case. Time from the start of mitoxantrone to the detection of AML was 13, 48, and 72 months, respectively. Before SWOG 9921, there were no cases of mitoxantrone-induced AML reported in patients treated for prostate cancer.

CONCLUSION

The emergence of this possible pattern of secondary malignancy emphasizes the importance of randomized controlled trials in defining safety and efficacy of new approaches for patients in the adjuvant setting.

Disruption of the ETV6 gene as a consequence of a rare translocation (12;12)(p13;q13) in treatment-induced acute myeloid leukemia after breast cancer

We describe a case of treatment-induced acute myeloid leukemia M2 after breast cancer with a rare reciprocal t(12;12)(p13;q13) as a secondary cytogenetic abnormality in addition to the t(11;19)(q23;p13.1). Fluorescence in situ hybridization analysis revealed that both ETV6 genes (previously TEL) were located on the same der(12)t(12;12) as a result of t(12;12). Interestingly, the translocated ETV6 gene was disrupted, indicating the breakpoint on the large der(12)t(12;12) to be within the ETV6 gene and thus the possible formation of a new fusion gene. CHOP gene at 12q13, was found to be translocated intact to the other homologue chromosome 12, indicating that the breakpoint on the small der(12) is proximal to CHOP. To the best of our knowledge, our patient represents the first report of the rare t(12;12)(p13;q13) described in treatment-induced leukemia and the possible formation of a new fusion gene.

Therapy-related acute myelogenous leukemia and myelodysplastic syndrome

Therapy-related acute myelogenous leukemia and myelodysplastic syndrome (t-AML/MDS) are increasing in prevalence with aging of the population and improved survival of patients treated with chemotherapy or radiotherapy for other malignancies. Research focused on the pathogenesis of t-AML/MDS will provide insight into the pathogenesis of de novo AML/MDS. Participation in clinical trials should be encouraged for this patient population because results with available treatment options are clearly suboptimal.

Benzene-induced acute myeloid leukemia: a clinician's perspective

Benzene-induced acute myeloid leukemia (AML) is considered a secondary form of AML, based both in theory and on limited cohort observations. Its latency, cytogenetic aberrations, and clinical features are thought similar to, or identical with, AML resulting from the use of modern day cytotoxic agents for chemotherapy and immunotherapy. Although distinction between secondary AML and the far more common de novo AML is difficult to establish with certainty in any given case, latency from toxic therapeutic and environmental exposure and certain clinical and pathological features generally separate these two entities. AML is the only human neoplasm proven to be potentially caused by benzene, which actually is an obsolete form of chemotherapy. Despite many years of environmental regulation, alleged toxic exposure to this ubiquitous chemical has become an expanding area of litigation. A review of benzene-induced AML suggests that, in developed countries, this entity should no longer merit serious consideration among workers in the modern petrochemical industry and related fields.

Is age an independent risk factor for chemically induced acute myelogenous leukemia in children?

Secondary or therapy-related acute myelogenous leukemia (t-AML) is a rare but unfortunate consequence of treatment with certain classes of cytotoxic chemotherapeutic agents or chronic exposure to high concentrations of benzene. Drugs known to produce AML following chemotherapy of primary malignancy are usually alkylating agents or topoisomerase II inhibitors. Both children and adults develop AML following treatment with these classes of antineoplastic drugs. In this review, the effect of age at treatment on a child's susceptibility to developing therapy related AML was investigated. The clinical literature describing pediatric cancer patients treated with cytotoxic chemotherapeutic agents was used to characterize risk factors associated with chemical leukemogenesis in children. As demonstrated in the published literature, the risk of developing AML following chemotherapy is not reliably correlated with the age of the pediatric patient. There is no consistent evidence that indicates that younger children will be at increased risk; in fact, some studies suggest that younger children might actually display a decreased susceptibility. The age dependency of treatment-related malignancies (all types) in children appears to vary considerably with the type of secondary neoplasm in question. For example, secondary solid tumors such as breast, central nervous system (CNS), bone, and thyroid cancer are highly dependent on the age of the patient at time of diagnosis and treatment; in contrast, an age dependency for t-AML risk was not observed in these same patient populations. Predictably, the induction of t-AML in children follows a rational dose-response relationship, with increasing doses of chemotherapy resulting in greater risk. Recent U.S. Environmental Protection Agency (EPA) cancer risk assessment guidance recommends a default assumption that children are inherently up to 10-fold more sensitive than adults to carcinogen exposures. Available scientific and medical literature does not support the hypothesis that children necessarily possess an increased risk of developing AML following leukemogenic chemical exposure.

Dexrazoxane-associated risk for acute myeloid leukemia/myelodysplastic syndrome and other secondary malignancies in pediatric Hodgkin's disease

PURPOSE

Pediatric Oncology Group (POG) studies 9426 and 9425 evaluated dexrazoxane (DRZ) as a cardiopulmonary protectant during treatment for Hodgkin's disease (HD). We evaluated incidence and risk factors of acute myeloid leukemia (AML)/myelodysplastic syndrome (MDS) and second malignant neoplasms (SMNs).

PATIENTS AND METHODS

Treatment for low- and high-risk HD with doxorubicin, bleomycin, vincristine, and etoposide (ABVE) or dose-intensified ABVE with prednisone and cyclophosphamide (ABVE-PC), respectively, was followed by low-dose radiation. The number of chemotherapy cycles was determined by rapidity of the initial response. Patients were assigned randomly to receive DRZ (n = 239) or no DRZ (n = 239) concomitantly with chemotherapy to evaluate its potential to decrease adverse cardiopulmonary outcomes.

RESULTS

Ten patients developed SMN. Six of eight patients developed AML/MDS, and both solid tumors (osteosarcoma and papillary thyroid carcinoma) occurred in recipients of DRZ. Eight patients with SMN were first events. With median 58 months' follow-up, 4-year cumulative incidence rate (CIR) for AML/MDS was 2.55% +/- 1.0% with DRZ versus 0.85% +/- 0.6% in the non-DRZ group (P = .160). For any SMN, the CIR for DRZ was 3.43% +/- 1.2% versus CIR for non-DRZ of 0.85% +/- 0.6% (P = .060). Among patients receiving DRZ, the standardized incidence rate (SIR) for AML/MDS was 613.6 compared with 202.4 for those not receiving DRZ (P = .0990). The SIR for all SMN was 41.86 with DRZ versus 10.08 without DRZ (P = .0231).

CONCLUSION

DRZ is a topoisomerase II inhibitor with a mechanism distinct from etoposide and doxorubicin. Adding DRZ to ABVE and ABVE-PC may have increased the incidence of SMN and AML/MDS.

Is secondary leukemia an independent poor prognostic factor in acute myeloid leukemia?

Secondary leukemia is a poorly defined term that often refers to the development of acute myeloid leukemia (AML) following the history of a previous disease, such as a myelodysplastic syndrome or a chronic myeloproliferative disorder. Secondary leukemia can also be a consequence of treatment with chemotherapy, including alkylating agents and topoisomerase II inhibitors, and/or radiotherapy, or due to exposure to environmental carcinogens. Outcomes for this large and variable group of patients with secondary AML have been poor compared to people who develop AML de novo. The question arises whether a diagnosis of secondary leukemia per se indicates a poor prognosis or whether their bad outcomes result from an association with certain morphologic and biologic characteristics. Morphologic dysplasia in de novo AML is related to unfavorable cytogenetics, but has no independent prognostic relevance under the conditions of intensive chemotherapy. While there is no significant correlation between cytogenetic risk groups and dysplasia, cytogenetic features do have an impact on outcome among both de novo and secondary AML patients. In various subgroups of secondary AML, the spectrum of cytogenetic abnormalities is similar to de novo AML, but the frequency of abnormalities associated with unfavorable and intermediate risk cytogenetics, such as a complex karyotype, trisomy 8, monosomy 7, and others, is higher in secondary AML. The survival of patients with therapy-related myeloid leukemia (t-AML) is generally shorter than for those with de novo AML within the same cytogenetic risk group. Across the population of t-AML, however, survival varies according to cytogenetic risk group, with longer survival in patients with favorable-risk karyotypes. The term secondary AML is too broad and imprecise to be of importance and should not be used. These AML patients should be enrolled on front-line chemotherapy trials and should be stratified by pretreatment disease status and exposure history, if necessary. Most importantly, the molecular and genetic differences that appear to determine the phenotype and the outcome of these patients need to be investigated further.

Rare CBFB-MYH11 fusion transcripts in AML with inv(16)/t(16;16) are associated with therapy-related AML M4eo, atypical cytomorphology, atypical immunophenotype, atypical additional chromosomal rearrangements and low white blood cell count: a study on 162 patients

The spectrum of CBFB-MYH11 fusion transcripts in acute myeloid leukemia (AML) M4eo with inv(16)/t(16;16) is heterogeneous. Approximately 85% show type A CBFB-MYH11 fusion transcripts. In addition, more than 10 different fusion transcripts have been reported. The prognostic impact and biological background of rare fusion transcripts remain open. In this study, a molecular characterization of CBFB-MYH11 transcripts in 162 patients with CBFB-MYH11 positive AML at diagnosis was performed. In total, 128 patients (79.0%) showed the fusion transcript type A, whereas nine different rare CBFB-MYH11 fusion genes were detected in 34 cases (21.0%). Rare fusion transcripts were found more frequently in therapy-related AML (P=0.0106). Numerical gains of the chromosomes 8, 21 and 22 were more frequently associated with type A (28.3%) than with rare fusions (12.9%) (P=0.012). Median white blood cell (WBC) count was higher in type A (35.4 G/l; range=1.1-279 G/l) than in cases with rare types (7.8 G/l; range=0.8-148.0 G/l) (P<0.0001). Rare fusion transcripts were correlated with an atypical cytomorphology not primarily suggestive for the FAB subtype M4eo (P=0.0203). Immunophenotype revealed lower CD2, CD13, CD33 and CD90 levels than in type A fusion cases (P=0.036, 0.002, 0.029 and 0.045, respectively). However, the type of fusion was not an independent prognostic parameter.

Etiology and management of therapy-related myeloid leukemia

The diagnosis of therapy-related myeloid leukemia (t-MDS/t-AML) identifies a group of high-risk patients with multiple and varied poor prognostic features. These neoplasms are thought to be the direct consequence of mutational events induced by cytotoxic therapy. Their outcomes have historically been poor compared with those of people who develop acute myeloid leukemia (AML) de novo. The question arises whether a diagnosis of t-AML per se indicates a poor prognosis, or whether their bad outcomes result from other clinical and biologic characteristics. Because of lingering damage from prior cytotoxic therapy and, in some cases, the persistence of their primary disorder, patients with t-AML are often poor candidates for intensive AML therapy. The spectrum of cytogenetic abnormalities in t-AML is similar to de novo AML, but the frequency of unfavorable cytogenetics, such as a complex karyotype or deletion or loss of chromosomes 5 and/or 7, is higher in t-AML. Survival varies according to cytogenetic risk group, with better outcomes observed in patients with t-AML with favorable-risk karyotypes. Treatment recommendations should be based on performance status and karyotype. Patients with t-AML should be enrolled on front-line chemotherapy trials, appropriate for de novo AML patients with similar disease characteristics. Allogeneic hematopoietic cell transplantation can cure some patients with t-AML. Most important , the molecular and genetic differences that appear to determine the phenotype and the outcome of these patients need to be investigated further.

Topoisomerase II and the etiology of chromosomal translocations

Acute leukemias with balanced chromosomal translocations, protean morphologic and immunophenotypic presentations but generally shorter latency and absence of myelodysplasia are recognized as a complication of anti-cancer drugs that behave as topoisomerase II poisons. Translocations affecting the breakpoint cluster region of the MLL gene at chromosome band 11q23 are the most common molecular genetic aberrations in leukemias associated with the topoisomerase II poisons. These agents perturb the cleavage-religation equilibrium of topoisomerase II and increase cleavage complexes. One model suggests that this damages the DNA directly and leads to chromosomal breakage, which may result in untoward DNA recombination in the form of translocations. This review will summarize the evidence for topoisomerase II involvement in the genesis of translocations and extension of the model to acute leukemia in infants characterized by similar MLL translocations.

Formaldehyde as a potential human leukemogen: an assessment of biological plausibility

The International Agency for Research on Cancer (IARC, 2004) recently reevaluated the epidemiological data on formaldehyde and concluded that there was "strong but not sufficient evidence for a causal association between leukaemia and occupational exposure to formaldehyde." This conclusion was tempered since a mechanism for leukemia induction could not be identified. Chemically induced leukemia is a well-studied phenomenon with benzene and a number of cancer chemotherapeutic drugs recognized as capable of causing this effect. Abundant in vitro and in vivo data in animals and humans demonstrate that exposure to sufficient doses of these recognized leukemogens can initiate a cascade of events leading to hematopoietic toxicity and the subsequent development of leukemia. This review addresses the biological plausibility that formaldehyde might be capable of causing any type of leukemia by providing a broad overview of the scientific data that must be considered in order to support or refute a conclusion that a particular substance might be leukemogenic. Data on benzene and selected chemotherapeutic cancer drugs are used as examples and are briefly summarized to demonstrate the similar biological events thought to result in leukemogenesis. These data are compared and contrasted with the available data on formaldehyde in order to judge whether they fulfill the criteria of biological plausibility that formaldehyde would be capable of inducing leukemia as suggested by the epidemiological data. Based on the epidemiological data, it is reasonable to expect that if formaldehyde was capable of inducing leukemia, in vivo and in vitro data would offer supporting evidence for biological plausibility. In particular, there is (1) no evidence to suggest that formaldehyde reaches any target organ beyond the site of administration including the bone marrow, (2) no indication that formaldehyde is toxic to the bone marrow/hematopoietic system in in vivo or in vitro studies, and (3) no credible evidence that formaldehyde induces leukemia in experimental animals. As discussed in this review, based on the key biological events that occur in the process of chemically induced leukemia, there is inadequate biological evidence currently available to corroborate existing weak epidemiological associations. This provides an insufficient database to conclude that there is a causal relationship for formaldehyde and leukemia risk.

High-risk neuroblastoma treated with tandem autologous peripheral-blood stem cell-supported transplantation: long-term survival update

PURPOSE

To provide an update on long-term survival of patients with high-risk neuroblastoma treated with tandem cycles of myeloablative therapy and peripheral-blood stem-cell rescue (PBSCR).

PATIENTS AND METHODS

Ninety-seven patients with high-risk neuroblastoma were treated between 1994 and 2002. Patients underwent induction therapy with five cycles of standard agents, resection of the primary tumor and local radiation, and two consecutive courses of myeloablative therapy (including total-body irradiation) with PBSCR.

RESULTS

Fifty-one patients have experienced relapse or died. Median follow-up time among the 46 patients who remain alive without progression is 5.6 years (range, 15.1 months to 9.9 years). Progression-free survival (PFS) rate at 5 years from diagnosis was 47% (95% CI, 36% to 56%), and PFS rate at 7 years was 45% (95% CI, 34% to 55%). Overall survival rate was 60% (95% CI, 48% to 69%) and 53% (95% CI, 40% to 64%) at 5 and 7 years, respectively. The 5- and 7- year PFS rates from time of first transplantation for 82 patients who completed both transplants were 54% (95% CI, 42% to 64%) and 52% (95% CI, 40% to 63%), respectively. Five patients died from treatment-related toxicity after tandem transplantation. Relapse occurred in 37 (42%) of 89 patients, mainly within 3 years of transplantation and primarily in diffuse osseous sites. No primary CNS relapse or secondary leukemia was seen. One patient developed synovial cell sarcoma 8 years after therapy.

CONCLUSION

High-dose therapy with tandem autologous stem-cell rescue is effective for treating high-risk neuroblastoma, with encouraging long-term survival. CNS relapse and secondary malignancies are rare after this therapy.

Isochromosome 1q in a myelodysplastic syndrome after treatment for acute promyelocytic leukemia

A growing body of literature reports therapy-related myelodysplastic syndrome (t-MDS) and acute myeloid leukemia (t-AML) in patients treated successfully for acute promyelocytic leukemia (APL). We report a t-MDS with an isochromosome 1q as a sole abnormality, 47,XY,+1,i(1)(q10), in a 46-year-old man with APL 14 years after he was treated with cytosine arabinosine and daunorubicin. The literature on t-MDS/t-AML after APL therapy and on isochromosome 1q is reviewed.

Toxicity of the topoisomerase II inhibitors

Topoisomerase II inhibitors represent a broad class of antineoplastic agents with a wide spectrum of activity against malignancies. Topoisomerase II inhibitors include the anthracyclines, mitoxantrone and epipodophyllotoxins. Short-term toxicity includes myelosuppression and gastrointestinal toxicity. Long-term survivors are at risk of cardiac toxicity and secondary leukaemia. This article discusses these toxicities in detail, including administration of these agents to patients with hepatic and/or renal insufficiency, and the need for dose adjustments in selected patient populations.

Early G2/M checkpoint failure as a molecular mechanism underlying etoposide-induced chromosomal aberrations

Topoisomerase II (Topo II) inhibitors are cell cycle-specific DNA-damaging agents and often correlate with secondary leukemia with chromosomal translocations involving the mixed-lineage leukemia/myeloid lymphoid leukemia (MLL) gene on chromosome 11 band q23 (11q23). In spite of the clinical importance, the molecular mechanism for this chromosomal translocation has yet to be elucidated. In this study, we employed 2-color FISH and detected intracellular chromosomal translocations induced by etoposide treatment. Cells such as ataxia-telangiectasia mutated-deficient fibroblasts and U2OS cells, in which the early G2/M checkpoint after treatment with low concentrations of etoposide has been lost, executed mitosis with etoposide-induced DNA double-strand breaks, and 2-color FISH signals located on either side of the MLL gene were segregated in the postmitotic G1 phase. Long-term culture of cells that had executed mitosis under etoposide treatment showed frequent structural abnormalities of chromosome 11. These findings provide convincing evidence for Topo II inhibitor-induced 11q23 translocation. Our study also suggests an important role of the early G2/M checkpoint in preventing fixation of chromosomal abnormalities and reveals environmental and genetic risk factors for the development of chromosome 11 translocations, namely, low concentrations of Topo II inhibitors and dysfunctional early G2/M checkpoint control.

Therapy-related myelodysplastic syndrome with inv(16)(p13q22) and I type CBFbeta/MYH11 after autologous transplantation: undetectable fusion transcript in pretransplant progenitor cells

We describe here a unique case of therapy-related myelodysplastic syndrome (t-MDS) with inv(16)(p13q22) after autologous stem cell transplantation for lymphoma. The rare and smallest I type CBFbeta/MYH11 fusion transcript with a breakpoint at nucleotide 399 of CBFbeta and at nucleotide 2134 of MYH11 was detected in the bone marrow cells by reverse transcription polymerase chain reaction analysis. However, the fusion transcript was undetectable in the pretransplant peripheral blood stem cells. These results suggest that the stem cell damage leading to t-MDS may be induced mainly by the conditioning regimen for transplantation. Taken together with previous reports, the I type fusion transcript is preferentially induced with chemotherapy.

Hematologic aspects of myeloablative therapy and bone marrow transplantation

The transplantation of bone marrow cells or isolated hematopoietic stem cells from the bone marrow or peripheral blood is a widely utilized form of therapy for patients with incurable diseases of the hematopoietic and immune systems. Successful engraftment of the transplanted stem cells in an adequately prepared recipient normally leads to bone marrow reconstitution over a period of several weeks, accompanied by more gradual reconstitution of the immune system. Since the recipient is profoundly ill during the initial treatment period, laboratory data is critical for monitoring engraftment, detecting residual/recurrent disease, and identifying problems that may delay bone marrow reconstitution or lead to other medical complications. Accurate blood cell counts are imperative, and most bone marrow transplantation patients undergo periodic monitoring with bone marrow aspirates and biopsies with cytogenetic, molecular, and multiparametric flow cytometric studies. The potential complications of bone marrow transplantation include engraftment failure and delayed engraftment, infection, residual bone marrow disease, acute and chronic graft versus host disease, myelofibrosis, therapy-related acute leukemia, post-transplant lympho-proliferative disorders, and toxic myelopathy.

Do children have increased susceptibility for developing secondary acute myelogenous leukemia?

This study was undertaken to evaluate the effects of age on a child's susceptibility to developing leukemia following exposure to known leukemogenic agents. The clinical literature describing the risk of developing acute myelogenous leukemia (AML) following treatment with alkylating agents or topoisomerase reactive drugs (known leukemogens) was used as a basis for this investigation. Based on this preliminary assessment, the age of the child does not appear to be an independent variable for risk following treatment with either class of drug. Although the number of studies and cases was very small, the available scientific and medical literature does not support the hypothesis that children will necessarily have an altered susceptibility or increased risk of developing chemotherapy-induced AML.

DNA topoisomerase II in therapy-related acute promyelocytic leukemia

BACKGROUND

Chromosomal translocations leading to chimeric oncoproteins are important in leukemogenesis, but how they form is unclear. We studied acute promyelocytic leukemia (APL) with the t(15;17) translocation that developed after treatment of breast or laryngeal cancer with chemotherapeutic agents that poison topoisomerase II.

METHODS

We used long-range polymerase chain reaction and sequence analysis to characterize t(15;17) genomic breakpoints in therapy-related APL. To determine whether topoisomerase II was directly involved in mediating breaks of double-stranded DNA at the observed translocation breakpoints, we used a functional in vitro assay to examine topoisomerase II-mediated cleavage in the normal homologues of the PML and RARA breakpoints.

RESULTS

Translocation breakpoints in APL that developed after exposure to mitoxantrone, a topoisomerase II poison, were tightly clustered in an 8-bp region within PML intron 6. In functional assays, this "hot spot" and the corresponding RARA breakpoints were common sites of mitoxantrone-induced cleavage by topoisomerase II. Etoposide and doxorubicin also induced cleavage by topoisomerase II at the translocation breakpoints in APL arising after exposure to these agents. Short, homologous sequences in PML and RARA suggested the occurrence of DNA repair by means of the nonhomologous end-joining pathway.

CONCLUSIONS

Drug-induced cleavage of DNA by topoisomerase II mediates the formation of chromosomal translocation breakpoints in mitoxantrone-related APL and in APL that occurs after therapy with other topoisomerase II poisons.

Therapy-related myeloid leukaemia: a model for leukemogenesis in humans

Therapy-related myeloid leukemia (t-AML) is a distinctive clinical syndrome occurring after exposure to chemotherapy (CT) or radiotherapy (RT). We studied 306 consecutive patients referred to the University of Chicago with cytogenetic analyses. Since 1972, 141 males and 165 females with a median age of 51 years (range: 3-83 years) at primary diagnosis and 58 years (range: 6-86 years) at secondary diagnosis were analyzed. Patients had received various cytotoxic agents including alkylating agents (240 patients, 78%) and topoisomerase II inhibitors (115 patients, 39%). One hundred and twenty-one (40%) had received CT alone, 43 (14%) had received RT alone, and 139 (45%) had received both modalities. At diagnosis of t-AML, 282 (92%) had clonal abnormalities involving chromosome 5 (n=63), chromosome 7 (n=85), both chromosomes 5 and 7 (n=66), recurring balanced rearrangements (n=31), or other clonal abnormalities (n=39); 24 had a normal karyotype. Abnormalities of chromosomes 5 and/or 7 accounted for 76% of all cases with an abnormal karyotype. Seventeen patients had developed t-AML after autologous stem cell transplantation, but no unique pattern of cytogenetic abnormalities was observed. Patients presenting with acute leukemia were more likely to have a balanced rearrangement than those presenting with myelodysplasia (28% versus 4%, p<0.0001). Shorter latency was observed for patients with balanced rearrangements (median: 28 months versus 67 months; p<0.0001). Median survival after diagnosis of t-AML was 8 months; survival at 5 years was less than 10%. To gain insights into the molecular basis of this disease, we performed gene expression profiling of CD34+ hematopoietic progenitor cells from t-AML patients. We found distinct subtypes of t-AML that have characteristic gene expression patterns. Common to each of the subgroups are gene expression patterns typical of arrested differentiation in early progenitor cells. Leukemias with a -5/del(5q) have a higher expression of genes involved in cell cycle control (CCNA2, CCNE2, CDC2), checkpoints (BUB1), or growth (MYC), and loss of expression of the gene encoding interferon consensus sequence-binding protein (ICSBP). A second subgroup of t-AML is characterized by down-regulation of transcription factors involved in early hematopoiesis (TAL1, GATA1, and EKLF) and overexpression of proteins involved in signaling pathways in myeloid cells (FLT3) and cell survival (BCL2). Establishing the molecular pathways involved in t-AML may facilitate the identification of selectively expressed genes that can be exploited for the development of targeted therapies.

Secondary acute promyelocytic leukemia following chemotherapy for non-Hodgkin's lymphoma in a child

Of the several kinds of therapy-related leukemia, therapy-related acute promyelocytic leukemia (t-APL) is most closely associated with topoisomerase II inhibitor administration for treatment of malignancies in adults. Although rare in children, the majority of therapy-related malignancies have been etoposide-related APL associated with Langerhans cell histiocytosis. The authors describe the development of t-APL after chemotherapy administered for non-Hodgkin's lymphoma (NHL) in an 8-year-old girl. One month after cessation of the 3-year chemotherapy regimen of doxorubicin and other agents but not etoposide or radiotherapy, the patient was diagnosed with t-APL with positive PML-RARA molecular abnormality. The patient attained a complete remission following treatment with all-trans retinoic acid-containing chemotherapy. Thereafter, she successfully received hematopoietic stem cell transplantation from an HLA-matched sibling donor. Development of t-APL associated with NHL in children appears to be rare.

Karyotype is an independent prognostic parameter in therapy-related acute myeloid leukemia (t-AML): an analysis of 93 patients with t-AML in comparison to 1091 patients with de novo AML

The aim of this study was to compare the pattern of karyotype abnormalities of therapy-related acute myeloid leukemia (t-AML) (n=93) with de novo AML (n=1091), and to evaluate their impact on prognosis. Favorable, intermediate, and unfavorable cytogenetics were observed in 25.8, 28.0, and 46.2% of t-AML, and in 22.2, 57.3, and 20.4% of de novo AML. The median overall survival (OS) was shorter in t-AML than in de novo AML (10 vs 15 months, P=0.0007). Favorable and unfavorable cytogenetics had a prognostic impact with respect to OS in both t-AML (P=0.001 and 0.0001) and de novo AML (P<0.0001 and <0.0001). To define the overall prognostic impact of cytogenetics and t-AML, a multivariate Cox's regression analysis was performed for OS with favorable cytogenetics, unfavorable cytogenetics, t-AML, age, and white blood cell (WBC) count as covariates. All parameters proved to be independently related to OS (P=0.001 for t-AML, P<0.0001 for all other parameters). Within patients with t-AML, there were significant correlations between OS and both unfavorable (P<0.0001) and favorable cytogenetics (P=0.001), while age and WBC count had no impact on OS. In conclusion, these data indicate that cytogenetics are an important prognostic parameter in t-AML. Furthermore, t-AML is an unfavorable factor independent of cytogenetics with respect to survival.

[Chromosomal abnormalities in secondary myelodysplastic syndromes and leukemias]

Secondary leukemias group essentially together myelodysplastic syndromes and acute leukemias, therapy-related (chemo- or radio-), or consecutive to environmental factors. It's now proven that some recurrent abnormalities are associated with effects of therapeutic agents, as -5/del(5q), -7/del(7q) linked to alkylating agents, or 11q23 and 21q22 abnormalities linked to inhibitors of Topoisomerase II. Even if important differences between secondary and "de novo" forms exist, the discrimination between these 2 categories is not always obvious: many common chromosomal abnormalities, "de novo" leukemias in older patients having characteristics close to those of postalkylating leukemias, neonatal forms possibly secondary to maternal affect. Recent studies identified some others chromosomal abnormalities in the secondary leukemias and confirmed the poor prognosis of these hemopathies. This review sums up criterions, circumstances and cytogenetic abnormalities.

[The interest of standard and molecular cytogenetics for diagnosis of acute leukemia]

The standard and molecular cytogenetic techniques now belong to the panel of mandatory analyses performed at diagnosis of acute leukemia. Chromosomal abnormalities contribute to define different types of leukemias and present the major advantage to be effective and independent prognostic factors, essential for therapeutic choices. Cytogenetic techniques allowing to identify hyperdiploïdy >50 chromosomes, t(12;21)(p13;q22)/TEL-AML1(ETV6-CBFA2), t(9;22)(q34;q11)/BCR-ABL, 11q23/MLL, t(15;17)(q22;q12-21)/PML-RARalpha, t(8;21)(q22;q22)/AML1-ETO and inv(16)(p13q22)/ CBFbeta/MYH11 are developed. Among the techniques devoted to study genome, cytogenetics is a basic, simple and effective tool for giving a total picture of the genome through karyotype. Maintaining a systematic cytogenetic analysis is essential, not only because cytogenetics now belongs to routine practice but also because it still contributes to better defining morpho-immunologic sub-types of leukemia, to identify new cytogenetic entities and to understand hematopoiesis and leukemogenesis.

[Chromosomal abnormalities in acute myeloid leukaemias]

Cytogenetic studies of acute myeloid leukaemias reveal non-random chromosomal abnormalities in 50-70% of karyotypes. Some are correlated with morphological and immunological parameters and constitute a prognostic factor independent of the other factors of risk: favourable for acute leukaemias myeloid with translocations t(8;21), t(15;17) and inversion or translocation of the chromosome 16, inv(16)/t(16;16), poor with deletion of the long arm of chromosome 5 del(5q), rearrangement of the 11q23 region and complex karyotypes. The distribution of the anomalies depends on the age: 11q23 and t(8;21) more frequent for the child, del(5q) and complex anomalies more frequent for the adult. The karyotypes are essential for the diagnosis, the follow-up of the patients and the evaluation of the relapse. It plays a fundamental part in the detection of new genes and their partners implied in the leucemogenese. The knowledge of their function is essential to open new therapeutic ways.

Classification of acute leukemias

Because of the increasing recognition of the importance of genetic events to the diagnosis and treatment of the acute leukemias, the proposed new World Health Organization (WHO) classification incorporates genetic aberrations and immunology as major defining features in addition to morphology. In a hierarchal approach, genetic changes have precedence in the acute myeloid leukemias and immunology and genetic changes have precedence in the acute lymphoblastic leukemias. Four major groups of acute myeloid leukemia are recognized: 1) Acute myeloid leukemias with recurrent genetic abnormalities, 2) Acute myeloid leukemia with multilineage dysplasia, 3) Acute myeloid leukemias, therapy related, and 4) Acute myeloid leukemia not otherwise categorized. Two types of acute lymphoblastic leukemia are recognized based on immunologic characteristics: precursor B lymphoblastic leukemia/lymphoma and precursor T lymphoblastic leukemia/lymphoma. Precursor B acute lymphoblastic leukemia/lymphoma is subclassified into prognostic genetic groups. Biphenotypic leukemia is recognized as a form of acute leukemia of ambiguous lineage.

Clinical-cytogenetic associations in 306 patients with therapy-related myelodysplasia and myeloid leukemia: the University of Chicago series

Therapy-related myelodysplasia and myeloid leukemia (t-MDS/t-AML) is a distinctive clinical syndrome occurring after exposure to chemotherapy (CT) or radiotherapy (RT). We report findings on 306 consecutive patients referred to our institution with morphologic review and cytogenetic analyses. Since 1972, 141 males and 165 females with a median age of 51 years (range, 3-83 years) at primary diagnosis and 58 years (range, 6-86 years) at secondary diagnosis were analyzed. Patients had been administered various cytotoxic agents, including alkylating agents (240 patients, 78%) and topoisomerase 2 inhibitors (115 patients, 39%). One hundred twenty-one (40%) had undergone CT alone, 43 (14%) had undergone RT alone, and 139 (45%) had undergone both modalities. At diagnosis of t-MDS/t-AML, 282 (92%) had clonal abnormalities involving chromosome 5 (n = 63), chromosome 7 (n = 85), chromosomes 5 and 7 (n = 66), recurring balanced rearrangements (n = 31), other clonal abnormalities (n = 39), or normal karyotype (n = 24). Abnormalities of chromosome 5, 7, or both accounted for 76% of all cases with an abnormal karyotype. Seventeen patients acquired t-MDS/t-AML after autologous stem cell transplantation, but no unique pattern of cytogenetic abnormalities was observed. Shorter latency was observed for patients with balanced rearrangements (median, 28 vs 67 months; P <.0001). Patients with acute leukemia were more likely to have balanced rearrangement than those with myelodysplasia (28% vs 4%; P <.0001). Median survival time after diagnosis of t-MDS/t-AML was 8 months; survival at 5 years was less than 10%. These data confirm and extend previous associations between clinical, morphologic, and cytogenetic findings in t-MDS/t-AML.

Therapy-related acute promyelocytic leukemia

PURPOSE

To analyze patient cases of therapy-related acute promyelocytic leukemia (tAPL), occurring after chemotherapy (CT), radiotherapy (RT) or both for a prior disorder, diagnosed during the last 20 years in three European countries.

PATIENTS AND METHODS

The primary disorder and its treatment, interval from primary disorder to tAPL, characteristics of tAPL, and its outcome were analyzed in 106 patients.

RESULTS

Eighty of the 106 cases of tAPL were diagnosed during the last 10 years, indicating an increasing incidence of tAPL. Primary disorders were predominantly breast carcinoma (60 patients), non-Hodgkin's lymphoma (15 patients), and other solid tumors (25 patients). Thirty patients had received CT alone, 27 patients had received RT alone, and 49 patients had received both. CT included at least one alkylating agent in 68 patients and at least one topoisomerase II inhibitor in 61 patients, including anthracyclines (30 patients), mitoxantrone (28 patients), and epipodophyllotoxins (19 patients). Median interval from primary disorder to tAPL diagnosis was 25 months (range, 4 to 276 months). Characteristics of tAPL were generally similar to those of de novo APL. With treatment using anthracycline-cytarabine-based CT or all-trans-retinoic acid combined with CT, actuarial survival was 59% at 8 years.

CONCLUSION

tAPL is not exceptional, and develops usually less than 3 years after a primary neoplasm (especially breast carcinoma) treated in particular with topoisomerase II-targeted drugs (anthracyclines or mitoxantrone and less often etoposide). Characteristics and outcome of tAPL seem similar to those of de novo APL.