Cytogenetic and Southern blot analysis to demonstrate clonality and to estimate prognosis in patients with myelodysplastic syndromes

We examined the bone marrow of 109 patients with myelodysplastic syndrome ( MDS) at the time of diagnosis and during the course of the disease by means of Southern blot analysis and/or cytogenetic studies to detect and evaluat e clonal markers, their implications for the prognosis of the disease, and the response to treatment. The patients either were enrolled in an EORTC st udy and received low-dose Ara-C with (n = 31) or without (n = 21) growth fa ctors, according to the study protocol, or were treated supportively (only one patient received regular chemotherapy for concomitant lymphoma). Full o r at least partial remission was achieved by 34% of the treated patients (n = 54). In 57% (53 of 93) of all patients a clonal marker of either kind wa s detected by Southern blot analysis and/or cytogenetic examination. Clonal chromosomal aberrations were found in 45% (35 of 77) of the cases examined at diagnosis, with solitary del(5q) aberrations occurring in 10% of the ca ses and complex aberrations in 18%, trisomy 8 or monosomy 7 being a frequen t finding. Of all patients, 49% (28 of 57) were characterized by one or mor e gene rearrangements (e.g., Ig-JH, TcR-beta, M-bcr, GM-CSF, G-CSF, or IL-3 ) at diagnosis. In five of 21 cases (24%) studied in hematological remissio n of the disease chromosomal aberrations were still detectable, and in seve n of 23 (30%) a gene rearrangement persisted. We also found six cases with multiple clones exhibiting different susceptibilities to treatment and ther eby indicating the oligoclonal character of this disease. Clinical evaluati on revealed that the prognosis of the respective patients was directly rela ted to the particular clonal markers detected at diagnosis: Risk groups wer e subdivided according to the karyotypes, with a solitary del(5q) aberratio n meaning a favorable, a normal karyotype an intermediate, solitary aberrat ions without del(5q) a poor, and complex karyotypes a very poor prognosis. We showed that densitometry helps to increase the sensitivity of Southern b lot analysis by quantifying the amount of altered DNA, which often increase s shortly before or at progression of MDS, Overall, there was a high level of concordance of both clonality examinations with the clinical course of t he disease and the response rate. Therefore, we recommend cytogenetic studi es and Southern blot analysis to detect clonal markers at diagnosis of MDS, to detect oligoclonality and clonal evolution, or to quantify the amount o f clonal DNA, which appears to be a sensitive tool for evaluating the progn osis and response to therapy in MDS.