Myelodysplastic syndromes: their history, evolution and relation to acute myeloid leukaemia

Myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are a family of myeloid cancers with diverse genotypes and phenotypes characterized by ineffective haematopoiesis and risk of transformation to acute myeloid leukaemia (AML). Some epidemiological data indicate that MDS incidence is increasing in resource-rich regions but this is controversial. Most MDS cases are caused by randomly acquired somatic mutations. In some patients, the phenotype and/or genotype of MDS overlaps with that of bone marrow failure disorders such as aplastic anaemia, paroxysmal nocturnal haemoglobinuria (PNH) and AML. Prognostic systems, such as the revised International Prognostic Scoring System (IPSS-R), provide reasonably accurate predictions of survival at the population level. Therapeutic goals in individuals with lower-risk MDS include improving quality of life and minimizing erythrocyte and platelet transfusions. Therapeutic goals in people with higher-risk MDS include decreasing the risk of AML transformation and prolonging survival. Haematopoietic cell transplantation (HCT) can cure MDS, yet fewer than 10% of affected individuals receive this treatment. However, how, when and in which patients with HCT for MDS should be performed remains controversial, with some studies suggesting HCT is preferred in some individuals with higher-risk MDS. Advances in the understanding of MDS biology offer the prospect of new therapeutic approaches.

Navigating the contested borders between myelodysplastic syndrome and acute myeloid leukemia

Myelodysplastic syndrome and acute myeloid leukemia are heterogeneous myeloid neoplasms which arise from the accumulation of mutations in a myeloid stem cell or progenitor that confer survival or growth advantages. These disease processes are formally differentiated by clinical, laboratory, and morphological presentations, especially with regard to the preponderance of blasts in the peripheral blood or bone marrow (AML); however, they are closely associated through their shared lineage as well as their existence on a spectrum with some cases of MDS displaying increased blasts, a feature that reflects more AML-like behavior, and the propensity for MDS to transform into AML. It is increasingly recognized that the distinctions between these two entities result from the divergent patterns of genetic alterations that drive each of them. Mutations in genes related to chromatin-remodeling and the spliceosome are seen in both MDS and AML arising out of antecedent MDS, while mutations in genes related to signaling pathways such as RAS or FLT3 are more typically seen in AML or otherwise are a harbinger of transformation. In this review, we focus on the insights into the biological and genetic distinctions and similarities between MDS and AML that are now used to refine clinical prognostication, guide disease management, and to inform development of novel therapeutic approaches.

The use of biomonitoring data in exposure and human health risk assessment: benzene case study

Abstract A framework of "Common Criteria" (i.e. a series of questions) has been developed to inform the use and evaluation of biomonitoring data in the context of human exposure and risk assessment. The data-rich chemical benzene was selected for use in a case study to assess whether refinement of the Common Criteria framework was necessary, and to gain additional perspective on approaches for integrating biomonitoring data into a risk-based context. The available data for benzene satisfied most of the Common Criteria and allowed for a risk-based evaluation of the benzene biomonitoring data. In general, biomarker (blood benzene, urinary benzene and urinary S-phenylmercapturic acid) central tendency (i.e. mean, median and geometric mean) concentrations for non-smokers are at or below the predicted blood or urine concentrations that would correspond to exposure at the US Environmental Protection Agency reference concentration (30 µg/m(3)), but greater than blood or urine concentrations relating to the air concentration at the 1 × 10(-5) excess cancer risk (2.9 µg/m(3)). Smokers clearly have higher levels of benzene exposure, and biomarker levels of benzene for non-smokers are generally consistent with ambient air monitoring results. While some biomarkers of benzene are specific indicators of exposure, the interpretation of benzene biomonitoring levels in a health-risk context are complicated by issues associated with short half-lives and gaps in knowledge regarding the relationship between the biomarkers and subsequent toxic effects.

Thrombocytopenia in myelodysplastic syndromes and myelofibrosis

Myelodysplastic syndromes (MDS) are a group of hematopoietic stem cell disorders characterized by ineffective hematopoeisis and an increased risk of transforming to acute myelogenous leukemia (AML). Determining the molecular basis of the disease has been hampered by its heterogeneity. Thrombocytopenia is often a manifestation of MDS and needs to be monitored and treated accordingly. Treating the underlying disorder with a variety of differentiation and immunosuppressive agents alleviates the problem in a small percentage of patients but more often complicates the issue. Several treatments used for primary immune thrombocytopenic purpura (ITP) have been tried in MDS patients, though with only modest success rates. Preliminary studies suggest that the use of a thrombopoietic growth factor may afford substantial increases in platelet levels without excessive deleterious side effects. Primary myelofibrosis (MF) is a chronic myeloproliferative disorder associated with hepatosplenomegaly and refractory cytopenias. Immunomodulatory agents have shown promise in treating the anemia associated with this MF. However, there are currently no standard therapies to treat the thrombocytopenia that is often found in patients with this disease.

Myelodysplastic syndromes with del(5q): indications and strategies for cytogenetic testing

Cytogenetics is a major predictor of disease behavior and treatment outcome in myelodysplastic syndromes (MDS). Deletion of the long arm of chromosome 5, del(5q), is the most common chromosomal abnormality found in patients with MDS. The development of lenalidomide (Revlimid; Celgene, Summit, NJ) as an effective targeted therapy for low/intermediate-risk MDS with a del(5q) has increased the importance of karyotyping in disease management. In the present review, the importance of an accurate cytogenetic diagnosis in del(5q) MDS, its impact on prognosis, and the effect it can have on the choice of treatment was discussed. In addition, the strengths and limitations of conventional and novel cytogenetic testing techniques currently available for patients with del(5q) MDS were evaluated. A practical diagnostic algorithm was provided to help facilitate the early detection and optimal treatment of MDS patients with a del(5q) abnormality. While the gold standard for genetic testing remains metaphase karyotyping, emerging novel molecular techniques such as fluorescence in situ hybridization may provide clinically valuable complementary and supplemental data.

Myelodysplastic syndrome (MDS), acute myeloid leukaemia (AML) and chronic myeloproliferative disorder (CMPD) in cats

Histological, enzyme histochemical and ultrastructural findings in three cases of feline bone marrow neoplasia are described. The following changes were observed: in myelodysplastic syndrome (MDS), a low medullary blast count, strongly atypical (micromegakaryocytic) proliferative megakaryocytopoiesis, hypoplastic erythrocytopoiesis with impairment of differentiation, multifocal extravasation and lymphoid aggregates; in acute myeloid leukaemia (AML), medullary proliferation of undifferentiated cell types; in chronic myeloIproliferative disorder (CMPD), trilinear medullary proliferation with complete cellular maturation, osteomyelosclerosis and extramedullary haemopoiesis. In two cases (MDS, AML), ultrastructural demonstration of C-type virus particles (feline leukaemia virus) suggested a viral aetiology.

Bone marrow dysplasia in patients with newly diagnosed acute myelogenous leukemia does not correlate with history of myelodysplasia or with remission rate and survival

BACKGROUND

The records and initial bone marrow studies of 106 patients with newly diagnosed acute myelogenous leukemia (AML) were analyzed retrospectively to determine whether bone marrow dysplasia was predictive of a previous myelodysplastic disorder or correlated with remission rate and survival.

METHODS

Bone marrow aspirates and biopsy specimens were reviewed in a blinded fashion; dysplasia was assessed in as objective a manner as possible by numerically scoring nine specific findings: erythrocyte multinuclearity, nuclear fragmentation, megaloblastic characteristics, leukocyte granulation abnormalities and nuclear malformations, Pelger-Huet cells, and megakaryocytic dysplasia (mononuclear megakaryocytes, micromegakaryocytes, and megakaryocytes with multiple distinct nuclei).

RESULTS

Dysplasia of the megakaryocytic line was seen in 34% of patients; 70% of the patients had erythrocyte dysplasia; and 68% had leukocyte dysplasia. Pelger-Huet cells were seen in bone marrow of 35% of the patients. Overall dysplasia score and specific dysplastic findings such as Pelger-Huet cells did not correlate with a known history of myelodysplasia (P = 0.47), cytogenetic abnormalities (P = 0.35), prior chemotherapy treatment with or without alkylating agents (P = 1.00), previous malignant disorders such as polycythemia vera (P = 1.00), remission rate (P = 0.93), or survival (P = 0.42). Multivariate analysis confirmed known independent risk factors for remission in this patient population, including age (P = 0.04), history of prior chemotherapy (P = 0.04), abnormalities in chromosomes 5, 7, or 8 (P = 0.02), and type of antileukemia therapy (P < 0.001).

CONCLUSIONS

Bone marrow dysplasia is common in patients with AML and does not correlate with a history of myelodysplasia or predict outcome when patients are treated with standard intensive AML therapy.

Cytogenetic analysis of bone marrow from patients with primary myelodysplastic syndrome

Of 34 patients with primary myelodysplastic syndrome (MDS), 26 (76.5%) were found to have chromosome defects using an improved bone marrow culture method and high-resolution G-banding technique induced by actinomycin D. The frequency of abnormalities varied among the subtypes: 1/2 in refractory anaemia with ringed sideroblasts; 18/24 in refractory anaemia; 5/6 in refractory anaemia with excess of blasts (RAEB); and 2/2 in refractory anaemia with excess of blasts in transformation. The most frequent abnormalities, either single, double or complex defects, were -5/5q-, -7, +8 and +21; 16q-/16p-, +19 and -X were also common. The percentage of aneuploid cells, in particular hypodiploid cells, was increased. The abnormalities were detected more frequently in complex aberrations associated with RAEB and RAEB in transformation. The presence of -5/5q- as a sole aberration was associated with longer mean survival time (greater than 18 months) but multiple (more than two) chromosomal abnormalities were associated with a poorer prognosis and a mean survival time of only 7.5 months. Chromosome follow-up studies indicated that patients with -7, +8, +21, -X and complex defects, increased hypodiploid cells and karyotpic evolution were likely to have a high risk of transformation to leukaemia or to a more severe subtype of MDS with a short overall mean survival time. These defects, mostly of the deleted type, are assumed to play a specific role in the pathogenesis of myelodysplasia. Repeated chromosomal analyses during the clinical course convey more accurate prognostic criteria for patients.

Acute parvovirus B19 infection mimicking myelodysplastic syndrome of the bone marrow

A 36-year-old, previously healthy woman was referred to our institution with pancytopenia and splenomegaly for suspected acute leukemia. Bone marrow aspiration showed marked dysplastic changes, excess of blasts, and only spurious red blood cell precursors. Action was taken to prepare allogeneic bone marrow transplantation from an HLA identical sibling for myelodysplastic syndrome. Repeat cytological examination of the bone marrow revealed striking hyperplasia of the red cell line with presence of abnormal giant proerythroblasts. Acute parvovirus B19 infection was suspected and confirmed by detection of anti-B19 IgM and B19 DNA. The underlying disease for this transient aplastic crisis was a formerly unknown hereditary spherocytosis.

Exposure histories in acute nonlymphocytic leukemia patients with a prior preleukemic condition

A subset of patients with acute nonlymphocytic leukemia (ANLL) have evidence of a myelodysplastic syndrome (MDS), low infiltrate leukemia, or other preleukemic condition that may be present for several months before onset of disease. The hypothesis that these conditions act as markers for environmentally induced cancer was examined in 270 ANLL patients, 46 with a preleukemic phase and 224 with an acute onset. Although the effects of previously identified risk factors (male sex, age older than 50 years, prior cytotoxic therapy) were demonstrated, no associations with common environmental conditions (cigarette smoking, alcohol use, occupations with exposure to chemicals or radiation) were present with the exception of hobbies involving potential chemical exposure, odds ratio (OR) and 95% confidence intervals = 4.2 (1.4 to 12.3) and self-reported exposure to pesticides, OR = 10.2 (1.8 to 63.1). These may be chance associations although a previous case-control study of MDS reported similar findings.

Monoclonal antibody ratios in malignant myeloid diseases: diagnostic and prognostic use in myelodysplastic syndromes

Based on a 6 1/2-year study of bone marrows (BM) from 74 consecutive adult patients with newly diagnosed primary myelodysplastic syndromes (MDS), we have evaluated the role of immunophenotyping (IP) for subclassification purposes with a selected panel of monoclonal antibodies (Mab). Compared to normal BM IP revealed increased numbers of Mab-defined immature myeloid cells (defined by Mab MY7 [CD13] and MY9 [CD33] (P less than 0.05). Furthermore, decreased numbers of mature myeloid cells (defined by Mab NAT-9 II:3F-6F [NAT-9]) (P less than 0.001) were demonstrated in all French-American-British (FAB) subtypes except refractory anaemia with sideroblasts (RA-S). Since expression of CD13 and CD33 antigens on immature myeloid cells is variable, IP based on a single Mab was often found to be non-informative. However, the construction of myeloid antibody ratios (MAR), designed to give higher figures with increasing numbers of immature myeloid cells and/or decreasing numbers of mature myeloid cells in the BM, disclosed increasing mean ratio values with progressing FAB subtypes. More significant however, was that different prognostic subgroups based on the MAR could be identified independently of the FAB classification. We conclude that the use of IP--especially when MAR is included--is useful in prognostic scoring systems in MDS.

Differentiation induction therapy of myelodysplastic syndromes

Myelodysplastic syndromes are a heterogenous group of haemopoietic stem cell disorders characterized by dysplastic haematopoiesis and a defective maturation of a slowly expanding or sometimes of a stable population of haemopoietic progenitors. Defective maturation, which may involve one or more of the marrow cell lineages is regarded as the central pathophysiological feature of myelodysplastic syndromes. Patients with myelodysplastic syndromes respond poorly to conventional cytotoxic chemotherapy, frequently developing a prolonged marrow aplasia. The alternative and more appropriate form of therapy is differentiation induction therapy. The results of few preliminary clinical studies in myelodysplastic patients showed that a combination of differentiating agents is superior to single agent differentiation therapy. An extensive pre-clinical screening of the response of fresh cells from myelodysplastic patients in primary culture is needed to establish the optimal doses and conditions for significant synergies between various differentiating agents followed by large controlled randomized clinical trials based on differentiation induction therapy for patients with myelodysplastic syndromes.

Bone marrow karyotype and prognosis in primary myelodysplastic syndromes

Bone marrow karyotype, survival time, and the rate of progression to leukaemia were studied in 111 unselected patients with primary myelodysplastic syndromes. The 49 patients (44%) with clonal chromosome aberrations had survival time (median 29 months) similar to that found in the 62 patients with normal bone marrow karyotype (24 months, p greater than 0.10). The presence of multiple (greater than 2) abnormalities (17 patients) was strongly associated with poor prognosis, with a median survival of only 7 months (p less than 0.001). Prognostic information could be attributed to 2 specific abnormalities, del(5q) and -7: Presence of del(5q) as the sole anomaly was associated with long survival (36+ months), whereas monosomy 7 was a bad prognostic sign (6 months). The risk for leukaemia development correlated neither with the number of chromosome abnormalities nor with any particular anomaly. Our findings demonstrate the prognostic importance of quantifying the complexity of bone marrow chromosome changes. They also emphasize that different specific abnormalities convey widely different prognostic information in primary myelodysplastic syndromes.

Differentiation induction in myelodysplasia and acute myeloid leukaemia: use of synergistic drug combinations

DNA synthesis inhibitors and vincristine greatly enhance the response of leukaemic and dysplastic cells to differentiation inducing agents such as retinoic acid (RET). Differentiation induction therapy is an attractive therapeutic approach in myelodysplasia (MDS) and in acute myeloid leukaemia (AML) in the elderly, since it should be possible to increase the production of mature cells, at the expense of precursor cells, without incurring the complications of intensive cytotoxic therapy. Single agent differentiation therapy has, however, not been highly successful. We have therefore investigated the use of synergistic combinations of agents. We treated nine patients (6 with MDS, 3 with AML) with 13-cis-retinoic acid (up to 100 mg/m2/day) in combination with either 6-thioguanine (20-40 mg/day in 14-57 day courses) or with vincristine (1-2 mg as a single injection during a four-day course of RET). Seven patients responded with an increase in the mature cells of at least one haemopoietic lineage. A concomitant decrease in marrow blasts was observed in 3/4 responding patients. The retention of dysplastic and karyotypic abnormalities and lack of a hypoplastic phase all suggested that differentiation induction was occurring in vivo. Prior failure to respond to therapy with single agents (RET in two and cytosine arabinoside in five patients) suggests that the synergy observed in vitro operates in vivo. In-vitro studies on marrow cells from seven patients demonstrated synergistic differentiation induction in 6/7 samples. The seventh patient was one of the two who did not respond clinically. The second of these clinically unresponsive patients had cells which were relatively refractory to RET in vitro, suggesting that in-vivo and in-vitro responses may be related.