INTRODUCTION: Myelodysplastic syndromes are dynamic diseases affecting the stem cell compartment in bone marrow presenting with different clinical courses ranging from stable, indolent disease to rapid progression to acute myeloid leukemias. So far, only 3 studies on karyotype analysis in MDS with a minimum of 30 patients have been published. Most knowledge about genetic evolution in MDS is based on the description of parallely existing subclones within one single examination. Thus, little is known about the real frequency, the time spans and the clinical impact of karyotype evolution.

MATERIALS AND METHODS: So far, data from 322 patients with MDS or secondary AML and at least two successfully performed classical cytogenetic analyses are available from four centres of the Competence Network Acute and Chronic Leukemias. As yet, we retrospectively examined 268 patients out of this data set. Karyotype evolution (KE) was defined as acquisition of additional aberrations, expansion of an aberrant clone (>20%) or development of a completely aberrant karyotype after an initial mosaic karyotype.

RESULTS: In 44 cases (16%) KE was observed. In the mean 2.8 (range 2–9) cytogenetic examinations have been performed. In 27 cases additional aberrations occurred and in 17 cases the abnormal clone expanded in a subsequent analysis. Compared to stable courses, patients with KE had a tendency towards a shorter survival (p=0.15).

In the group of patients with expansion of the aberrant clone the most frequent karyotypes were −7/7q- (4x), complex (3x), 5q- (3x) and +8 (3x). The most frequent karyotypes in which during the course of the disease additional aberrations occurred were complex (4x) and karyotypes with two miscellaneous aberrations (4x). The most frequent additional aberrations were 5q- (3x) and −17/17p- (3x).

CONCLUSIONS: In sequential cytogenetic examinations KE is a frequent event. Patients with KE tend to have a shortened survival. In our collective no long-term survivor could be observed in the group displaying KE regardless of the therapy strategies (excluding allogeneic transplantation). In this multicentric study which encompasses the largest data base on sequential analyses in MDS to date, frequency, evolution patterns and prognostic relevance of karyotype changes have been studied allowing a better insight into the genetic dynamics of MDS.

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