Cytogenetic, clinical, and cytologic characteristics of radiotherapy-related leukemias

Chronic Myeloid Leukemia Following Treatment for Primary Neoplasms or Other Medical Conditions

OBJECTIVES

Therapy-related chronic myeloid leukemia (CML) has been reported, but its clinical presentation and pathologic features have not yet been well characterized.

METHODS

Twenty-one cases of CML following treatment for primary diseases were collected and retrospectively analyzed.

RESULTS

The clinical presentation, pathologic features, and cytogenetic profile were similar to de novo CML. In particular, those with an isolated Philadelphia chromosome constituted 88.9% of our cases, and additional aberrations characteristic of therapy-related acute myeloid leukemia/myelodysplastic syndrome (AML/MDS) were not identified in this study. The patients responded to imatinib/derivatives and survived with limited follow-up.

CONCLUSIONS

Therapy-related CML has a clinical presentation, pathologic features, and cytogenetic profile akin to de novo CML. Absence of additional significant aberrations seems to suggest a pathogenesis different from therapy-related AML/MDS. Therapy-related CML exhibits a robust therapeutic response to imatinib/derivatives and favorable clinical outcomes similar to de novo CML.

Lymphohematopoietic cancers induced by chemicals and other agents and their implications for risk evaluation: An overview

Lymphohematopoietic neoplasia are one of the most common types of cancer induced by therapeutic and environmental agents. Of the more than 100 human carcinogens identified by the International Agency for Research on Cancer, approximately 25% induce leukemias or lymphomas. The objective of this review is to provide an introduction into the origins and mechanisms underlying lymphohematopoietic cancers induced by xenobiotics in humans with an emphasis on acute myeloid leukemia, and discuss the implications of this information for risk assessment. Among the agents causing lymphohematopoietic cancers, a number of patterns were observed. Most physical and chemical leukemia-inducing agents such as the therapeutic alkylating agents, topoisomerase II inhibitors, and ionizing radiation induce mainly acute myeloid leukemia through DNA-damaging mechanisms that result in either gene or chromosomal mutations. In contrast, biological agents and a few immunosuppressive chemicals induce primarily lymphoid neoplasms through mechanisms that involve alterations in immune response. Among the environmental agents examined, benzene was clearly associated with acute myeloid leukemia in humans, with increasing but still limited evidence for an association with lymphoid neoplasms. Ethylene oxide and 1,3-butadiene were linked primarily to lymphoid cancers. Although the association between formaldehyde and leukemia remains controversial, several recent evaluations have indicated a potential link between formaldehyde and acute myeloid leukemia. The four environmental agents examined in detail were all genotoxic, inducing gene mutations, chromosomal alterations, and/or micronuclei in vivo. Although it is clear that rapid progress has been made in recent years in our understanding of leukemogenesis, many questions remain for future research regarding chemically induced leukemias and lymphomas, including the mechanisms by which the environmental agents reviewed here induce these diseases and the risks associated with exposures to such agents.

Acute myeloid leukemia and myelodysplastic syndromes after radiation therapy are similar to de novo disease and differ from other therapy-related myeloid neoplasms

PURPOSE

Therapy-related myeloid neoplasms (t-MN) represent a unique clinical syndrome occurring in patients treated with chemotherapy and/or external-beam radiation (XRT) and are characterized by poorer prognosis compared with de novo disease. XRT techniques have evolved in recent years and are associated with significantly reduced bone marrow exposure. The characteristics of post-XRT t-MN in the current era have not been studied.

PATIENTS AND METHODS

We analyzed patients who developed acute myeloid leukemia (AML) or myelodysplastic syndromes (MDS) after XRT alone (47 patients) or cytotoxic chemotherapy/combined-modality therapy (C/CMT, 181 patients) and compared them with patients with de novo MDS or AML (222 patients). We estimated bone marrow exposure to radiation and compared the clinical, pathologic, and cytogenetic features and outcome of the XRT patients with the C/CMT patients and with patients with de novo MDS and AML.

RESULTS

Patients with t-MN after XRT alone had superior overall survival (P = .006) and lower incidence of high-risk karyotypes (P = .01 for AML and < .001 for MDS) compared with patients in the C/CMT group. In contrast, there were no significant differences in survival or frequency of high-risk karyotypes between the XRT and de novo groups.

CONCLUSION

AML and MDS diagnosed in the past decade in patients after receiving XRT alone differ from t-MN occurring after C/CMT and share genetic features and clinical behavior with de novo AML/MDS. Our results suggest that post-XRT MDS/AML may not represent a direct consequence of radiation toxicity and warrant a therapeutic approach similar to de novo disease.

Therapy-related myeloid neoplasms: pathobiology and clinical characteristics

Therapy-related myeloid neoplasms (t-MNs) are serious long-term consequences of cytotoxic treatments for an antecedent disorder. t-MNs are observed after ionizing radiation as well as conventional chemotherapy including alkylating agents, topoisomerase-II-inhibitors and antimetabolites. In addition, adjuvant use of recombinant human granulocyte-colony stimulating factor may also increase the risk of t-MNs. There is clinical and biological overlap between t-MNs and high-risk de novo myelodysplastic syndromes and acute myeloid leukaemia suggesting similar mechanisms of leukaemogenesis. Human studies and animal models point to a prominent role of genetic susceptibilty in the pathogenesis of t-MNs. Common genetic variants have been identified that modulate t-MN risk, and t-MNs have been observed in some cancer predisposition syndromes. In either case, establishing a leukaemic phenotype requires acquisition of somatic mutations - most likely induced by the cytotoxic treatment. Knowledge of the specific nature of the initiating exposure has allowed the identification of crucial pathogenetic mechanisms and for these to be modelled in vitro and in vivo. Prognosis of patients with t-MNs is dismal and at present, the only curative approach for the majority of these individuals is haematopoietic stem cell transplantation, which is characterized by high transplant-related mortality rates. Novel transplantation strategies using reduced intensity conditioning regimens as well as novel drugs - demethylating agents and targeted therapies - await clinical testing and may improve outcome. Ultimately, individual assessment of genetic risk factors may translate into tailored therapies and establish a strategy for reducing t-MN incidences without jeopardizing therapeutic success rates for the primary disorders.

Evidence for clustered tumour suppressor gene loci on mouse chromosomes 2 and 4 in radiation-induced acute myeloid leukaemia

PURPOSE

To investigate the influence of genetic and epigenetic factors on allelic loss on chromosomes 2 and 4 in mouse radiation-induced acute myeloid leukaemia (r-AML).

METHODS

r-AML that arose in (CBA/HxC57BL/6)F1xCBA/H and F1xC57BL/6 mice were screened for transcription factor PU1 (also known as SPI-1) gene mutations and methylation of the paired box gene 5 (Pax5) gene promoter. We have increased the statistical significance of a genetic linkage analysis of affected F1xCBA/H mice to test for linkage to loci implicated directly or indirectly with r-AML-susceptibility.

RESULTS

There was a statistically significant difference ( p < 10-4) in the frequency of PU1 gene mutations in F1xCBA/H and F1xC57BL/6 r-AML, implicating a second linked but genotype-dependent myeloid leukaemia suppressor gene on chromosome 2. A suggestive CBA/H r-AML-resistance locus maps within 10 cM of the minimally deleted region on chromosome 4. The Pax5 gene promoter is subject to ongoing subclonal promoter methylation in the r-AML, evidence that Pax5 gene silencing confers a selective advantage during clonal expansion in vivo.

CONCLUSIONS

Allelic loss in mouse r-AML and subsequent tumour suppressor gene mutation (PU1) or silencing (Pax5) is strongly influenced by genetic background and/or epigenetic factors, and driven by in vivo clonal selection.

Non-treatment-related chronic myeloid leukemia as a second malignancy

The characteristics of the very rare non-treatment-related chronic myeloid leukemia (nTr-CML) cases have never before been analyzed. The literature up to December 2002 was screened using the Medline database to identify cases of Tr-CML and nTr-CML. We considered five cases with nTr-CML identified among 270 newly diagnosed CML at our Department. Our report thus considers nine cases with nTr-CML compared to 77 affected by Tr-CML as a secondary neoplasm. The median age at the appearance of the first tumor was higher in nTr-CML patients compared to that of the Tr-CML group (P<0.0001). The median age at CML diagnosis was significantly higher in the nTr-CML than in the Tr-CML group (P<0.0001). The proportion of hematological malignancies as first tumor type was not different in the two groups (44% in nTr-CML versus 56% in Tr-CML). Our study underlines that nTr-CML as a second malignancy is a rare entity associated with elderly age.

DNA double strand breaks (DSB) and non-homologous end joining (NHEJ) pathways in human leukemia

DNA double strand breaks (DSB) are considered the most lethal form of DNA damage for eukaryotic cells. DSB can either be properly repaired, restoring genomic integrity, or misrepaired resulting in drastic consequences, such as cell death, genomic instability, and cancer. It is well established that exposure to DSB-inducing agents is associated with chromosomal abnormalities and leukemogenesis. The non-homologous end joining (NHEJ) pathway is considered a major route for the repair DSB in mammalian cells. Although the mechanism(s) by which repair of DSB lead to leukemia are poorly understood, recent evidence is beginning to emerge that a poorly defined and error-prone branch of the NHEJ pathway plays a pivotal role in this process. This review discusses some of the ways in which error-prone NHEJ repair may be involved in the development of genomic instability and leukemia.

Allelic loss on chromosome 4 (Lyr2/TLSR5) is associated with myeloid, B-lympho-myeloid, and lymphoid (B and T) mouse radiation-induced leukemias

The CBA/H mouse model of radiation-induced acute myeloid leukemia (AML) was re-examined using molecular approaches. In addition to the typical promyelocytic AMLs, 34% were reclassified as early pre-B lympho-myeloid leukemias (L-ML) based on leukemic blood cell morphology, immunoglobulin heavy-chain gene re-arrangements (IgH(R)), or expression of both lymphoid (Vpre-B1 and Rag1) and myeloid (myeloperoxidase and lysozyme M) genes. Allelic loss on chromosome 4 was frequently detected in AMLs (53%) and L-MLs (more than 95%), and the preferential loss of the maternally transmitted allele suggests the locus may be imprinted. A minimally deleted region (MDR) maps to a 3.4-cM interval, which is frequently deleted in radiation-induced thymic lymphomas (TLSR5) and contains a recessive, maternally transmitted genetic locus (Lyr2) that confers resistance to spontaneous and radiation-induced pre-B and T cell lymphomas, suggesting they are one and the same. Thus, the Lyr2/TLSR5 locus is frequently implicated in myeloid, lymphoid (B and T), and mixed-lineage mouse leukemias and lymphomas. Epigenetic inactivation of one Lyr2/TLSR5 allele during normal mouse development suggests that only a single hit is required for its inactivation during leukemogenesis, and this may be a significant contributing factor to the efficiency of the leukemogenic process in the mouse.

Secondary myelodysplasia with monosomy 7 arising after treatment for acute lymphoblastic leukemia in childhood

Monosomy 7 is recognized as a characteristic, clonal abnormality associated with acquired myelodysplasia (MDS) or acute myeloid leukemia (AML). It can occur as a late complication of cytotoxic therapy and is usually associated with exposure to alkylating agents or radiation therapy. We report two patients with therapy-related myelodysplasia (t-MDS) associated with monosomy 7 occurring in children after completion of therapy for acute lymphoblastic leukemia (ALL). Both children were noted to have t-MDS with monosomy 7 at the time of cessation of chemotherapy. Neither child had received an alkylating agent or radiation therapy during treatment. One child had a unique dicentric marker chromosome that was shown by fluorescent in situ hybridization to be derived from chromosome 7. This report emphasizes the need to identify and minimize therapy-related side effects without compromising cure rates.

Clinical and biological features of acute myeloid leukaemia occurring as second malignancy: GIMEMA archive of adult acute leukaemia

Between July 1992 and June 1996, 3934 new cases of acute leukaemia were registered in the Gruppo Italiano Malattie Ematologiche Maligne dell'Adulto (GIMEMA) Archive of Adult Acute Leukaemia. Two hundred cases (5.1%) presented with a history of primary malignancy (PM), 179 of which were acute myeloid leukaemia (AML). The median age of these cases was significantly higher than that of other primitive AML (63 years vs. 57 years; P < 0.001). The number of men was significantly lower than the number of women [74/1544 (4.8%) vs. 105/1420 (7.4%); odds ratio (OR) 0.63, 95% confidence interval (CI) 0.46-0.87; P < 0.002], as was the number of patients aged <65 years [104/1963 (5.3%) vs. 75/1001 (7.5%); OR 0.69, 95% CI 0.50-0.95; P < 0.01]. An increased incidence of cancer was observed among first-degree relatives of patients with AML occurring after a PM (secondary AML; sAML) [66/179 (36.9%) sAML vs. 757/2785 (27.2%) de novo AML, age adjusted; OR 2.62, 95% CI 1.07-6.42; P < 0.005]. Prevalent types of PM were breast cancer, lymphoma and Hodgkin's disease. sAML occurred after a median latency of 52 months (range 2-379). Of the 122 patients who received chemotherapy for sAML, 67 patients (55%) achieved a complete remission (CR), three a partial remission, 15 (12%) died in induction and 37 (30%) were unresponsive. The median duration of CR was 30 weeks (range 4-250). The median overall survival was 7 months (range 1-196). Comparing acute promyelocytic leukaemia with all other French-American-British (FAB) groups, a significant increase in CR achievement was observed [14/18 (77.7%) vs. 53/101 (52.4%), P < 0.046] as well as in median CR duration (55 vs. 24 months, P < 0.02). The analysis of our data suggests that not only previous chemotherapy but also genetic predisposition could play a role in the pathogenesis of sAML.

Cytogenetics of myelodysplasia and acute myeloid leukaemia in aircrew and people treated with radiotherapy

Increased risk of acute myeloid leukaemia has been reported in aircrew, possibly in association with cosmic radiation. We studied the cytogenetics of seven aircrew members who had acute myeloid leukaemia or myelodysplasia and found deletion or loss of chromosome 7 in four. The same abnormality was found in eight of 19 patients with leukaemia after radiotherapy alone. By comparison, only 81 of 761 unselected cases of myelodysplasia or acute myeloid leukaemia had the same cytogenetic abnormalities. Our results support the concept that deletions or loss of the long arm of chromosome 7 in myelodysplasia and acute myeloid leukaemia could indicate previous exposure to ionising radiation.

Therapy-related chronic myeloid leukemia: an epidemiological, clinical and pathogenetic appraisal

Second primary cancers represent an important complication of modern chemotherapy and radiotherapy. Therapy-related (tr) leukemias are among the most common second malignancies in both pediatric and adult populations. Whereas a reasonable amount of data is available regarding the epidemiology, molecular pathogenesis, clinical behavior and response to therapy of second primary acute leukemias, very little is known about therapy-related chronic myeloid leukemia (tr-CML). A better characterization of this entity could increase our understanding about the mechanisms of carcinogenesis, specially the induction of specific genetic abnormalities, e.g., BCR-ABL fusion, following chemotherapy and/or radiotherapy exposure, could facilitate the investigation of the kinetics of the development of CML, and also provide a model to study molecular events that might precede its development. Review of 32 tr-CML cases suggests that there are no clinically appreciable differences between tr-CML and de novo CML cases. Analysis of large epidemiological studies that investigated the risk of second primary leukemias has not shown any clear evidence of a higher risk of CML among individuals who underwent treatment for a primary cancer over the general population. The cancer-predisposing syndromes, the detection of BCR-ABL transcripts in healthy individuals, and the induction in vitro of BCR-ABL fusions by ionizing radiation, are all discussed in the context of tr-CML. Finally, the need for a large epidemiological study to specifically assess the risk of developing second primary CML after chemotherapy and/or radiotherapy is stressed.

Cytogenetic findings in 111 ovarian cancer patients: therapy-related chromosome aberrations and heterochromatic variants

The chromosomes of 111 ovarian cancer patients were studied in G- and C-banded slides from peripheral blood lymphocyte (PBL) cultures for chromosome damage caused by chemotherapy and radiotherapy and for asymmetry of the constitutive heterochromatin of chromosomes 1, 9, and 16. We also monitored the survival of these patients to determine whether any secondary neoplasia induced by the therapy and report the findings of our investigations. Melphalan (MEL) was the only drug used in single-drug chemotherapy. The incidence of chromosome abnormalities in melphalan-treated cells (25%) was higher than in the control group (17%). The incidence of structural changes was also higher (10.5%) in the MEL-treated group than in controls (6%). After treatments with combinations of drugs, the incidence of structural changes remained at the same level (11%). In the patients receiving combined treatment with MEL and radiation, the rate of structural changes increased dramatically (24%). The overall rate of chromosome aberrations in this group was also higher (50%). Combination of two or more drugs and radiation produced only 14% structural chromosome changes. The overall rate of chromosome aberrations was also low (20%) in this group. Of 111 patients studied, only 33 were alive 6 years after initiation of the study. Of the surviving patients, eight had rearranged chromosomes in the first analysis. After 5 years, new blood samples were collected from these patients and chromosome analyses showed abnormal karyotypes in all eight patients. All chromosome abnormalities in the second analysis were completely unrelated to those in the first analysis, however. Whether the chromosome changes in the second analysis were due to therapy or to other unknown factors could not be determined. Data on C-banding and the distribution of inversions indicated that 91% of the patients had C-band heteromorphisms of chromosomes 1, 91% had heteromorphisms of chromosome 9, and 69% had heteromorphisms of chromosome 16. Furthermore, inversions were observed in chromosome 1 (41% of patients), chromosome 9 (28% of patients), and chromosome 16 (5% of patients).

Age-related incidence and other epidemiological aspects of myelodysplastic syndromes

Although most haematologists perceive a rising prevalence and incidence of myelodysplastic syndromes (MDS), reliable epidemiological data on these disorders are largely lacking. The bone marrow register of the University of Düsseldorf allowed us to assess among other epidemiological features the incidence of MDS, which was compared to that of acute myeloid leukaemia (AML). Among a total of 18,416 different patients registered between 1975 and 1990, 584 cases of MDS (3.2%) and 506 cases of AML (2.8%) were identified. Over the study period, the percentage of newly diagnosed MDS rose from 1.3% to 4.5%, while there was no upward trend for AML. Among all patients undergoing bone marrow biopsy, the proportion of those over 60 years of age increased from 41.9% in 1975 to 54.1% in 1990. We found a strong correlation between the proportion of elderly patients and the relative frequency of MDS diagnoses. Thirty-one patients (5.3%) were classified as a secondary MDS because of previous treatment with cytotoxic chemotherapy and/or irradiation for a variety of malignancies. Twelve patients were identified in whom occupational exposure to organic solvents could not be ruled out. For calculating age-specific incidence rates, the analysis was confined to the town district of Düsseldorf (575,000 inhabitants), because exact demographical data were available for this population. In the last quinquennium of the study period (1986-90), myelodysplastic syndromes were more frequent than AML in the age group 50-70 years (4.9 v 1.8/100,000/year). In patients over 70, the incidence of MDS was more than 3 times that of AML (22.8 v 6.7/100,000). In this group, men had a higher incidence of MDS (33.9/100,000) than women (18/100,000). Crude annual incidence (all age groups) was also higher for MDS (4.1/100,000) than for AML (2.1/100,000) in recent years. We conclude that MDS are relatively common haematological neoplasias. The rising incidence in recent years is probably not due to changes in aetiological factors, but may reflect increased awareness on the part of physicians and extended use of diagnostic procedures in elderly patients.

Unbalanced 6p translocation as primary karyotypic anomaly in secondary acute nonlymphocytic leukemia

A case of acute nonlymphocytic leukemia after radiochemotherapy for Hodgkin's disease, with a rearrangement of 6p23 region, is described. This chromosome change, which has been previously reported in secondary leukemias or myelodysplastic syndromes, was an isolated karyotypic anomaly in our case, which strongly supports the nonrandom involvement of chromosome 6p in induced leukemias.

Chronic myelogenous leukemia after treatment with 131I for thyroid carcinoma. Report of a case and review of the literature

A patient who developed Philadelphia chromosome-positive chronic myelogenous leukemia (CML) 5 years after successful treatment for thyroid carcinoma, is reported. The Philadelphia chromosome was the typical 9;22 translocation. Southern blot analysis showed breakpoint cluster region rearrangement as observed in classical CML. Up to now, only two cases of CML have been reported following treatment for thyroid carcinoma. This rare complication has also been described after therapy for other malignancies. At present, it is not clear whether the development of CML after thyroid carcinoma represents a therapy-induced complication, a coincidence, or an increased susceptibility to secondary malignancies due to the malignant process itself.

Secondary acute non-lymphocytic leukemia with monosomy 7 arising 9 years after acute lymphoblastic leukemia in childhood

We report a case of pediatric acute non-lymphocytic leukemia (ANLL) with monosomy 7 occurring in a child successfully treated for acute lymphoblastic leukemia (ALL) nine years earlier. Acquired monosomy 7 is currently recognized as a distinct therapy-related cytogenetic abnormality which nonrandomly occurs as a late complication of cytotoxic therapy used in the treatment of both malignant and nonmalignant disease. Most commonly, this occurs as a disorder of bone marrow morphology and function characterized as a myelodysplastic syndrome (MDS) or ANLL. This case report emphasizes the need for continued evaluation of long-term survivors of childhood cancer to identify and minimize therapy-related side effects without compromising successful management.

Philadelphia chromosome-positive chronic myelogenous leukemia in treated Hodgkin's disease

A patient who developed Philadelphia (Ph) chromosome-positive chronic myelogenous leukemia (CML) 8 years after successful treatment for Hodgkin's disease (HD) is reported. The Ph chromosome with a typical 9(22) translocation was identified by banding techniques in 80% of bone marrow (BM) cells. Southern blot analysis showed breakpoint cluster region (BCR) rearrangement as observed in classical CML. Until now, only three cases of Ph + CML have been reported after treatment for HD. At present, it is not clear whether development of CML after HD represents a therapy-induced complication, an increased susceptibility to secondary malignancies owing to the malignant process itself, a consequence of the immunological deficiencies in HD, or possibly a genetic susceptibility to malignancy.

Chronic myelogenous leukemia following radiation therapy for testicular seminoma

A 43-year-old man was treated with orchiectomy and radiotherapy for testicular seminoma. Four years later, he developed a typical Philadelphia chromosome positive chronic granulocytic leukemia. Since the patient was not eligible for bone marrow transplantation, he was treated with busulfan. Long term follow-up of patients who received radiotherapy for testicular seminoma is warranted in order to detect possible secondary tumors.