Clinical and cytogenetic significance of myelodysplastic syndromes with disease evolution

Evolving concepts in myelodysplastic syndromes

Myelodysplastic syndromes continue to be "a riddle, wrapped in a mystery inside of an enigma". Clearly, MDS represent a heterogeneous group of disorders, and no uniform etiology or treatment can be prescribed for all patients. This further underscores the need for MDS patients to be seen at specialized centers and placed on experimental protocols if they need treatment. The important thing to remember is that ultimately, the patient must remain the measure of all things, and must be given all the therapeutic choices including that of waiting and watching with supportive care alone. Recent biologic insights have expanded the therapeutic options, but no curative therapies except stem cell transplants are available at this time. By dissecting the biology and focusing efforts towards understanding the etiology of the cytopenias, significant therapeutic advances are being made in this disease. The momentum built up so far must not be lost now.

Unique balanced chromosome abnormalities in treatment-related myelodysplastic syndromes and acute myeloid leukemia: report from an international workshop

A total of 123 balanced rearrangements, including 26 occurring as a sole anomaly, not known to be recurrent in myelodysplastic syndromes (MDS) or acute myeloid leukemia (AML) prior to the Workshop, were ascertained retrospectively from 104 patients with treatment-related MDS/AML (t-MDS/t-AML). Thirteen of the aberrations were reported previously in single cases and hence may be classified as recurrent as a result of the Workshop. Patients with Unique aberrations had complex karyotypes more often (P < 0.001 for all pairwise comparisons) than did other Workshop subgroups, with 72% having 3 or more aberrations. Among 85 cases with secondary chromosomal abnormalities, -5, -7, del(5q), and del(7q) were observed in 76%, which is significantly higher (P < or = 0.007 for all pairwise comparisons) than the frequencies found in the Workshop subgroups of patients with previously known recurring aberrations. The chromosome bands most often involved in balanced aberrations were 1p36 and 3q26-27. Treatment exposure was significantly different (less topoisomerase II inhibitor exposure, more radiotherapy-only exposure) than for patients with 11q23 (P < 0.001 and P = 0.002, respectively) and 21q22 (P = 0.007 and P = 0.002, respectively) abnormalities. The median time from the first toxic exposure to secondary disease, 59 months, was significantly longer (P < or = 0.016 for all significant pairwise comparisons) than the median latency of all other patients except those in the Rare subgroup, and the median survival time, 7 months, was significantly shorter than for patients in the 21q22, inv(16), and t(15;17) subgroups (P < or = 0.002 for all pairwise comparisons), but similar to patients in the 11q23 and Rare subgroups. In contrast to known recurring abnormalities, significantly more patients (61%, all P < 0.001) presented with t-MDS, with over one-third of these patients progressing to t-AML. Thus, this group of patients appears to be more similar to the typical t-MDS/t-AML patients, with complex karyotypes as well as chromosome 5 and 7 abnormalities, than to those with recurrent balanced rearrangements.

Telomere length in myelodysplastic syndromes

We have studied telomere length in the bone marrow cells or the granulocyte and lymphocyte cell fractions of 54 patients with myelodysplastic syndromes (MDS) by Southern blot hybridization using the (TTAGGG)4 probe. The average telomere length expressed as the peak telomere repeat array (TRA) in the peripheral blood, or bone marrow samples obtained from a group of 21 healthy age-matched controls (26-89 years old, mean age 55), ranged between 7.5 and 9.5 kb (mean peak TRA 8.6 kb). Twenty-four patients with refractory anemia (RA) were studied; 10/24 (42%) had telomere reduction (<7.5 kb) relative to age-matched controls and the mean peak TRA was 7.5 kb (range 4.0-9.0 kb). Eleven patients with RA with excess blasts (RAEB) were studied; 5/11 (45%) had reduced telomeres relative to age-matched controls and the mean peak TRA was 7.1 kb (range 5.0-9.0 kb). Eighteen patients with MDS in transformation to AML, comprising 15 with RAEB in transformation (RAEBt) and 3 with CMML in transformation (CMMLt), were also studied. Thirteen of eighteen patients (72%) had telomere reduction relative to age-matched controls and the mean peak TRA was 6.1 kb (range 3.5-9.0 kb). Thirty-six patients included in the study had either a normal karyotype or a simple karyotype (1 karyotypic change) and 20/36 (55%) of these had telomere reduction and the mean peak TRA was 7.1 kb (range 4.3-9.0 kb); 8 patients had a complex karyotype (3 or more karyotypic changes) and 5/8 (62%) of these had telomere reduction and the mean peak TRA was 6.1 kb (range 3.5-9.0 kb). We conclude, firstly that there is heterogeneity of telomere length in MDS and that this is observed throughout the spectrum of FAB-subtypes. Secondly, these data show that a marked reduction in telomere length in MDS if often associated with leukemic transformation and with the presence of complex karyotypic abnormalities.

Telomere dynamics and cytogenetic changes in human hematologic neoplasias: a working hypothesis

Chromosome termini, termed telomeres, provide important protection to avoid loss of master gene(s) that may exist at subtelomeric regions. Moreover, erosion of telomeres by cell division through end-replication problems resulted in telomeric-associated cytogenetic aberrations. To maintain a telomere length related to cell immortality, telomerase activity is upregulated in cancer cells, therefore, telomerase is considered to be a new marker of neoplasias. In this paper, we review and make suggestions regarding key aspects of telomere dynamics in both normal hematopoiesis and in malignant hematologic diseases.

Clinical aspects, cytogenetics and disease evolution in myelodysplastic syndromes

Myelodysplastic syndrome (MDS) is a morphologically characterized hematologic entity that is one of the clonal myeloproliferative disorders. Approximately 50 approximately 70% of MDS patients have cytogenetic abnormalities; these are usually chromosomal deletions, but some involve translocations such as t(1;7) (q10;p10). Translocations involving chromosomal regions 3q26 or 22q11 are often therapy-related. Recent studies have demonstrated that cytogenetic changes in MDS patients have clinical relevance. Accordingly, there are now scoring systems for predicting the prognoses of MDS patients. In this review, we describe the clinical significance of cytogenetic changes in MDS. We include MDS with some atypical forms, such as MDS with hypocellular bone marrow, MDS with minimal dysplasia, and MDS with myelofibrosis.

Diagnostic and prognostic significance of cytogenetics in adult primary myelodysplastic syndromes

Cytogenetic analysis has proven to be a mandatory part of the diagnosis of myelodysplastic syndromes (MDS) as well as a major indicator for predicting clinical course and outcome. This review concentrates on the cytogenetic classifications, the incidence and types of chromosome defects and the prognostic significance of the karyotype in adult primary MDS. Two cytogenetic classifications are currently used: one is based on the karyotype complexity (normal, single, double or complex defects), the other on clonal status (all metaphases normal, abnormal or admixture of normal and abnormal clones). Chromosome abnormalities are of both numerical and structural types. Aside from the 5q-syndrome, no specific clinico-cytogenetic entity has been reported. However, several distinct clinical and cellular features have been identified that correlate with the presence of specific chromosome defects such as inv(3)/t(3;3), +6, t(5;12), del(17p) and del(20q). The presence of complex defects is associated with reduced survival and a high risk of leukemic transformation. Among single defects, specific abnormalities may define distinct prognostic groups. Patients with del(5q) as a sole chromosome defect and a refractory anemia without excess of blasts have a favourable prognosis. For patients with trisomy 8 or monosomy 7 there may be distinct types of clinical evolution. Most patients with the 3q21q26 syndrome have a short survival. The presence of two chromosome defects may constitute an independent cytogenetic entity probably associated with relative poor prognosis. Karyotypic evolution generally represents a poor risk factor. The combination of cytogenetics with clinical and hematological features has proven to provide for a better prediction of patients' survival, leukemic transformation and response to treatment. Several scoring systems have been developed. They have to be improved by the study of new patients according to strict clinical and cytogenetic criteria and by the addition of newly recognized prognostic indicators such as histopathological features and molecular genetic mutations.

Hypocellular myelodysplastic syndromes (MDS): new proposals

To determine whether hypocellular MDS differs from normo/hypercellular MDS, we attempted to identify hypocellular MDS cases either by correcting the bone marrow (BM) cellularity by age (28 patients) or by using a single arbitrary value of BM cellularity (25 patients) and compared these two groups of hypocellular cases to the normo/hypercellular MDS cases (72 patients). 18 patients were common to both hypocellular groups. Patients with hypocellular MDS in both of these selected groups have similar features with regard to age and sex distribution, peripheral blood and bone marrow parameters, FAB subtypes, karyotypes, leukaemic transformation, and survival. However, the median age of patients in < 30% BM cellularity group was higher than those patients in the age-corrected group (69 years v 62 years). The selection of < 30% cellularity excluded 10 cases in the age group < 70 years but included another seven patients in the age group of > 70 years. However, correction of BM cellularity by age revealed that those included patients (selected for < 30% cellularity) who had normocellular BM by their age. Therefore we recommend the age-correcting grouping to ensure comparable series for comparison, for response to treatment, and survival. Finally, BM cellularity does not appear to be an important factor on prognosis in MDS, because patients with hypocellular MDS in both selected groups have similar prognosis to those with normo/hypercellular MDS patients.

Double-minute chromosomes appearing in a patient with myelodysplastic syndrome with disease evolution

We present the first case of a myelodysplastic syndrome (MDS) demonstrating an association between the appearance of double-minute chromosomes (dmin) and disease progression. This 59-year-old Japanese woman showed a deletion of the long arm of chromosome 5 [del(5)(q21q34)] and monosomy 9, when she was diagnosed as having refractory anemia with an excess of blasts (RAEB). Subsequential cytogenetic analyses demonstrated that the neoplastic cells in the peripheral blood had six copies of dmin, when the disease progressed into RAEB in transformation (RAEBt). This cytogenetic change was consistently observed when the patient developed the leukemia phase. The findings in this case suggest that the appearance of dmin may be linked to progression of the disease.