Refractory anaemia with preleukaemic polyclonal haemopoiesis and the emergence of monoclonal erythropoiesis on disease progression

The myelodysplastic syndromes: diagnosis and treatment

The myelodysplastic syndromes (MDSs) are common, acquired, clinically challenging hematologic conditions that are characterized by bone marrow failure and a risk of progression to acute leukemia. These disorders can arise de novo, especially in elderly patients or, less often, as a consequence of prior chemotherapy or radiotherapy for an unrelated disease. The MDS classification systems were revised recently and updated. These refined classification and prognostic schemes help stratify patients by their risk of leukemia progression and death; this knowledge can help clinicians select appropriate therapy. Although many treatments for MDS have been proposed and evaluated, at present, only hematopoietic stem cell transplantation offers any real hope for cure, and no available therapy beyond general supportive care offers benefit to more than a minority of patients. However, recent clinical trials enrolling patients with MDS have reported encouraging results with use of newer drugs, including lenalidomide, decitabine, and darbepoetin alfa. Other exciting treatment regimens are being tested. Here, we present a contemporary, practical clinical approach to the diagnosis and risk-stratified treatment of MDS. We review when to suspect MDS, detail how to evaluate patients who may have a form of the condition, explain key features of treatments that are currently available in the United States, and summarize a general, common-sense therapeutic approach to patients with MDS.

The myelodysplastic syndrome(s): a perspective and review highlighting current controversies

The myelodysplastic syndrome (MDS) includes a diverse group of clonal and potentially malignant bone marrow disorders characterized by ineffective and inadequate hematopoiesis. The presumed source of MDS is a genetically injured early marrow progenitor cell or pluripotential hematopoietic stem cell. The blood dyscrasias that fall under the broad diagnostic rubric of MDS appear to be quite heterogeneous, which has made it very difficult to construct a coherent, universally applicable MDS classification scheme. A recent re-classification proposal sponsored by the World Health Organization (WHO) has engendered considerable controversy. Although the precise incidence of MDS is uncertain, it has become clear that MDS is at least as common as acute myelogenous leukemia (AML). There is considerable overlap between these two conditions, and the former often segues into the latter; indeed, the distinction between AML and MDS can be murky, and some have argued that the current definitions are arbitrary. Despite the discovery of several tantalizing pathophysiological clues, the basic biology of MDS is incompletely understood. Treatment at present is generally frustrating and ineffective, and except for the small subset of patients who exhibit mild marrow dysfunction and low-risk cytogenetic lesions, the overall prognosis remains rather grim. In this narrative review, we highlight recent developments and controversies within the context of current knowledge about this mysterious and fascinating cluster of bone marrow failure states.

Favourable response to antithymocyte or antilymphocyte globulin in low-risk myelodysplastic syndrome patients with a 'non-clonal' pattern of X-chromosome inactivation in bone marrow cells

OBJECTIVE

Antithymocyte and antilymphocyte globulin (ATG/ALG) have a therapeutic effect in about 30% of patients with myelodysplastic syndromes (MDS). We were interested to know whether responding patients achieve clonal or polyclonal remissions.

PATIENTS

Ten women with low-risk MDS received either ALG or ATG. Before treatment and 3, 6, and 12 months later, X-chromosome inactivation patterns of peripheral blood T lymphocytes were compared with those of peripheral blood granulocytes or bone marrow cells, using the human androgen receptor gene assay and the phosphoglycerate kinase-1 assay.

RESULTS

Six women did not respond to therapy. Prior to treatment, four of them had a monoclonal, one had an oligoclonal, and one had a skewed X-chromosome inactivation pattern (XCIP). Four patients responded to ATG/ALG. Three of them were informative in our X-inactivation assays, and showed a non-clonal XCIP which did not change significantly after treatment with ATG/ALG.

CONCLUSION

A non-clonal XCIP in the bone marrow was associated with a response to ATG/ALG. Non-clonal XCIPs do not necessarily imply that there is no pathological clone. By definition, they just indicate that there is no evidence of a clone contributing more than 50% of cells in a sample. Non-clonal XCIPs may therefore be attributable to incomplete clonal expansion. This, in turn, might be explained by a vigorous immune attack against the MDS clone, which simultaneously causes collateral damage in the remaining normal haemopoiesis. In such patients, ATG/ALG may improve normal haemopoiesis by relieving the immunological pressure on the innocent bystanders.

Management of high-risk myelodysplastic syndromes

The myelodysplastic syndromes (MDS) are a group of clonal disorders characterized by one or more cytopenias secondary to bone marrow dysfunction. The percentage of bone marrow blasts, the number of cytopenic cell lines and cytogenetics define more precisely clinical risk groups. In the high-risk MDS, the time for evolution to acute myeloid leukemia (AML) is between 0.2 and 1.1 years and the median survival has been evaluated between 0.4 and 1.2 years. Progress in the understanding the biology of MDS and the development of accurate prognostic classification systems have allowed a risk-adapted treatment strategy in individual patients. Some high-risk MDS patient categories may benefit from intensive cytotoxic treatment. Allogeneic stem cell transplantation (alloSCT) from donors remains the treatment of choice for younger patients. Autologous stem cell transplantation (ASCT) may provide a suitable alternative for those patients without a sibling donor or for older patients' categories. New regimens using non-myeloablative stem cell transplantation followed by donor lymphocyte infusions (DLI) are underway and have achieved promising results in HLA-identical transplantation, resulting in reduced morbidity and mortality and confirming that this approach is feasible in patients ineligible for conventional allografting due to age and/or organ toxicity. Other therapeutic strategies include new low-dose treatments, antiapoptotic agents such as amifostine and anticytokine therapy, which are currently under investigation and deserve further evaluation. More insights into the biology of the disease, the discovery of new therapeutic approaches and the search for better ways to use existing strategies may lead to more effective treatments.

Dyshaemopoiesis in adults: a practical classification for diagnosis and management

Dyshaemopoiesis is a heterogeneous disease that may be classified into non-clonal and clonal dyshaemopoiesis. Non-clonal dyshaemopoiesis comprises reversible disorders with DNA synthesis impairment in dividing cells of the bone marrow by avitaminosis through various mechanisms or direct DNA damage from multiple causes. Complete haematologic recovery is obtained after vitamin supplementation or suppression of a myelotoxic agent. On the contrary, clonal dyshaemopoiesis is a group of chronic and usually irreversible diseases that may culminate in acute leukaemia (AL). These so called myelodysplastic syndromes (MDS) and their variants may be classified as primary, secondary and other diseases with doubtful clonality. A detailed classification of dyshaemopoiesis in adults may offer partial help in the diagnosis and management of dyshaemopoiesis. Pathobiological studies in progress allow better understanding of MDS and consequently the establishment of new modalities of treatment.

Bone marrow transplantation for myelodysplasia

Allogeneic bone marrow transplantation (BMT) is the only treatment modality that has consistently been demonstrated to cure patients with the myelodysplastic syndrome (MDS). Since the early 1980s, numerous publications have reported the results with BMT for over 700 patients with MDS and the lead patients are now disease-free for more than 16 years. Overall, these studies show that approximately 40% of patients are likely to be cured with allogeneic BMT. The best results have been reported for patients with refractory anemia who receive marrow from fully matched related donors, with 75% long-term disease-free survival rates. Factors that are associated with an increased risk of relapse and, thereby, shorter disease-free survival, include increased blast percentage and poor risk karyotype. Factors that are associated with an increased risk of non-relapse mortality and, in some studies, shorter disease-free survival, include longer disease duration, advanced patient age, therapy-related MDS, male patients, and use of mismatched or unrelated donors. However, favorable results have been seen in small studies of patients 55-66 years of age and in patients with refractory anemia undergoing matched unrelated donor BMT. Allogeneic BMT is appropriate therapy for patients with high or intermediate risk disease (risk category based on the International Prognostic Scoring System). The use of allogeneic BMT for patients with low risk disease is not well defined, but may be appropriate for particularly young individuals or those with a life-threatening single cytopenia.

Pathogenetic Aspects of Myelodysplastic Syndromes

The myelodysplastic syndromes (MDS) are acquired clonal disorders of the bone marrow. They were clearly defined in morphological terms by the French-American-British (FAB) group in 1982, as five conditions each with their own diagnostic criteria, but with the shared characteristics of ineffective blood cell production in one or more cell line, morphological dysplasia and a variable propensity to evolve into acute myeloid leukaemia (AML). In clinical practice patients typically present in old age with macrocytic anaemia, cytopenias, monocytosis and accumulation of marrow blast cells leading in time to fatal bone marrow failure or AML. To date treatment is unable to alter the natural history of MDS except in those few individuals who are able to undergo allogeneic progenitor cell transplantation.