Etiology and management of therapy-related myeloid leukemia

Long-term toxic effects of adjuvant chemotherapy in breast cancer

Breast cancer is the most common malignant tumor affecting women. Adjuvant systemic therapies have been shown to have a significant impact on reducing the risk for breast cancer recurrence and overall mortality. Chemotherapy remains an important and frequently used treatment option in the adjuvant setting, and the associated short-term adverse events are very well described. However, there is insufficient information regarding the long-term sequelae of most chemotherapeutic agents. In this review, we describe different potential long-term adverse events associated with adjuvant chemotherapy in breast cancer, with a particular focus on long-term cardiac toxicity, secondary leukemia, cognitive function, and neurotoxicity. In addition, we discuss the effect of adjuvant chemotherapy on fertility and sexual function of young breast cancer patients. These adverse events are frequently overshadowed by the well-demonstrated clinical efficacy and/or reassuring short-term safety profiles of the different chemotherapy regimens commonly used today. We believe that a proper understanding and appreciation of these adverse events will enable us to refine our strategies for managing breast cancer. The fact that adjuvant chemotherapy is often given to patients who might not really need it urges us to consider the whole spectrum of chemotherapy risks versus benefits to maximize benefit without compromising quality of life.

[Mitoxantrone-related acute leukemia by multiple sclerosis. Case report and practical approach by unclear cytopenia]

BACKGROUND

Mitoxantrone is highly efficacious in the treatment of severe multiple sclerosis (MS). Mitoxantrone therapy-related acute leukemia (TRAL) has recently become the focus of interest.

METHODS

A case report of fatal TRAL following mitoxantrone therapy is presented with a discussion on the differential diagnosis and risk factors. The interdisciplinary development of diagnostic and therapeutic algorithms is presented from a haematological and neurological point of view.

RESULTS

We describe the case of a 34-year-old MS patient who developed TRAL following mitoxantrone therapy (cumulative dose 45 mg/m(2) body surface). The patient died from endocarditis. TRAL is a rare but potentially fatal complication of mitoxantrone therapy with a wide variation of reported incidence. Thus far, no specific risk factors relating for example to preceding therapy and treatment regimens have been identified. Frequent laboratory controls and early bone marrow aspiration are mandatory for suspected TRAL as the condition is potentially curable.

CONCLUSIONS

TRAL needs to be considered in the risk-benefit assessment of mitoxantrone therapy, however, the exact incidence and risk factors (e.g. dosage, treatment regimen) are still unclear. The risks are controllable under close surveillance and early diagnosis is important for prognosis. Future investigations need to concentrate on identification of potential risk factors.

Haploinsufficiency of Apc leads to ineffective hematopoiesis

Loss of a whole chromosome 5 or a deletion of the long arm of chromosome 5, -5/del(5q), is a recurring abnormality in myeloid neoplasms. The APC gene is located at chromosome band 5q23, and is deleted in more than 95% of patients with a -5/del(5q), raising the question of whether haploinsufficiency of APC contributes to the development of myeloid neoplasms with loss of 5q. We show that conditional inactivation of a single allele of Apc in mice leads to the development of severe anemia with macrocytosis and monocytosis. Further characterization of the erythroid lineage revealed that erythropoiesis is blocked at the early stages of differentiation. The long-term hematopoietic stem cell (LT-HSC) and short-term HSC (ST-HSC) populations are expanded in Apc-heterozygous mice compared with the control littermates; however, the HSCs have a reduced capacity to regenerate hematopoiesis in vivo in the absence of a single allele of Apc. Apc heterozygous myeloid progenitor cells display an increased frequency of apoptosis, and decreased in vitro colony-forming capacity, recapitulating several characteristic features of myeloid neoplasms with a -5/del(5q). Our results indicate that haploinsufficiency of Apc impairs hematopoiesis, and raise the possibility that loss of function of APC contributes to the development of myelodysplasia.

Therapy related acute myeloid leukemia in breast cancer survivors, a population-based study

The aim of this study was to determine the association between age and stage at diagnosis of breast cancer with the subsequent development of acute myeloid leukemia (AML). The National Cancer Institute's Surveillance, Epidemiology, and End Results program were analyzed for incidence of second malignancies by age and stage at diagnosis of breast cancer. 420,076 female patients were identified. There was an age dependent risk of a subsequent diagnosis of AML in women younger than 50 years old (RR 4.14; P < 0.001) and women 50-64 years old (RR 2.19; P < 0.001), but not those 65 and older (RR 1.19; P = 0.123) when compared with the expected incidence of AML. A similar age dependent pattern was observed for second breast and ovarian cancers. There was also a stage dependent increase in risk of subsequent AML in younger women with stage III disease when compared with stage I disease (RR 2.92; P = 0.004), and to a lesser extent in middle age women (RR 2.24; P = 0.029), but not in older women (RR 0.79; P = 0.80).Younger age and stage III disease at the time of breast cancer diagnosis are associated with increased risk of a subsequent diagnosis of AML. This association maybe explained by either greater chemotherapy exposure or an interaction between therapy and genetic predisposition.

Genome-wide association study to identify novel loci associated with therapy-related myeloid leukemia susceptibility

Therapy-related acute myeloid leukemia (t-AML) is a rare but fatal complication of cytotoxic therapy. Whereas sporadic cancer results from interactions between complex exposures and low-penetrance alleles, t-AML results from an acute exposure to a limited number of potent genotoxins. Consequently, we hypothesized that the effect sizes of variants associated with t-AML would be greater than in sporadic cancer, and, therefore, that these variants could be detected even in a modest-sized cohort. To test this, we undertook an association study in 80 cases and 150 controls using Affymetrix Mapping 10K arrays. Even at nominal significance thresholds, we found a significant excess of associations over chance; for example, although 6 associations were expected at P less than .001, we found 15 (P(enrich) = .002). To replicate our findings, we genotyped the 10 most significantly associated single nucleotide polymorphisms (SNPs) in an independent t-AML cohort (n = 70) and obtained evidence of association with t-AML for 3 SNPs in the subset of patients with loss of chromosomes 5 or 7 or both, acquired abnormalities associated with prior exposure to alkylator chemotherapy. Thus, we conclude that the effect of genetic factors contributing to cancer risk is potentiated and more readily discernable in t-AML compared with sporadic cancer.

Acute leukemia as a secondary malignancy in children and adolescents: current findings and issues

Secondary acute leukemia is a devastating complication in children and adolescents who have been treated for cancer. Secondary acute lymphoblastic leukemia (s-ALL) was rarely reported previously but can be distinguished today from recurrent primary ALL by comparison of immunoglobulin and T-cell receptor rearrangement. Secondary acute myeloid leukemia (s-AML) is much more common, and some cases actually may be second primary cancers. Treatment-related and host-related characteristics and their interactions have been identified as risk factors for s-AML. The most widely recognized treatment-related risk factors are alkylating agents and topoisomerase II inhibitors (epipodophyllotoxins and anthracyclines). The magnitude of the risk associated with these factors depends on several variables, including the administration schedule, concomitant medications, and host factors. A high cumulative dose of alkylating agents is well known to predispose to s-AML. The prevalence of alkylator-associated s-AML has diminished among pediatric oncology patients with the reduction of cumulative alkylator dose and limited use of the more leukemogenic alkylators. The best-documented topoisomerase II inhibitor-associated s-AML is s-AML associated with epipodophyllotoxins. The risk of s-AML in these cases is influenced by the schedule of drug administration and by interaction with other antineoplastic agents but is not consistently found to be related to cumulative dose. The unpredictable risk of s-AML after epipodophyllotoxin therapy may discourage the use of these agents, even in patients at a high risk of disease recurrence, although the benefit of recurrence prevention may outweigh the risk of s-AML. Studies in survivors of adult cancers suggest that, contrary to previous beliefs, the outcome of s-AML is not necessarily worse than that of de novo AML when adjusted for cytogenetic features. More studies are needed to confirm this finding in the pediatric patient population.

Allogeneic stem cell transplantation in acute myeloid leukemia: establishment of indications on the basis of individual risk stratification

INTRODUCTION

Acute myeloid leukemia (AML) is a heterogeneous disorder with subtypes that differ considerably in morphology and in their underlying chromosomal and molecular aberrations, which, in turn, determine their prognosis. The establishment of the indications for allogeneic stem cell transplantation (SCT) therefore requires individualized risk stratification based on a combination of multiple diagnostic methods, including cytogenetic and molecular genetic studies, and immunophenotyping, as well as the sensitivity of the disease to chemotherapy.

METHODS

This article surveys the current strategies for establishing the indications for SCT in AML on the basis of a selective review of the relevant literature in the Medline database.

RESULTS

In patients with a high risk constellation-e.g., chromosome 7 anomalies, complex aberrations, or FLT3-length mutations-there is an indication for SCT in first remission. The balanced translocations t(15;17) and t(8;21), and the inversion inv(16) are prognostically favorable and are thus not considered an indication for SCT in first remission. The establishment of indications for stem cell transplantation also depends on the residual leukemic cell burden (minimal residual disease, MRD) as determined by the quantitative polymerase chain reaction or by flow cytometry, as well as an insufficient response to induction chemotherapy. Reduced-dose conditioning, a new technique that lessens acute toxicity, has been found to be associated with a 30% to over 50% two-year survival rate when used in the treatment of chemotherapeutically unresponsive or relapsing AML.

DISCUSSION

The indications for allogeneic SCT in AML should be further refined by more investigation in large studies.