Monitoring treatment efficiency in MDS at the molecular level; possibilities now and in the future.

Abstract

Myelodysplastic syndromes (MDS) are a heterogeneous group of bone marrow (BM) diseases. MDS patients suffer from bone marrow failure because of the expansion of a malignant clone, resulting in abnormal differentiation of blood cells and severe pancytopenias. MDS patients have a high propensity for the development of acute myeloid leukemia (AML). During the last few years it has become increasingly clear that MDS is a stem cell disease. Two methods have generally been used to study the clonal origin of MDS bone marrow cells. First, the combination of fluorescent in situ hybridization (FISH) in combination with cell sorting has been used to study MDS specific numerical chromosomal aberrations in various cell types. Secondly, the determination of the X-chromosome inactivation patterns (XCIP) in different cell types of female MDS patients has been used to study clonality irrespective of the presence of a disease-specific marker. Both techniques have also been used to monitor treatment efficiency. Both methods showed that a molecular remission occurred in approximately half of the patients who achieved complete clinical remission after intensive antileukemic treatment, depending on the study and the type of treatment. In case of cytogenetic analysis this proved to be of prognostic significance. This review discusses the advantages and disadvantages of both techniques for the determination of clonality at diagnosis as well as for the assessment of treatment efficiency in past and in ongoing clinical trials. Future directions and possibilities for further research are also discussed.