UICC World Cancer Congress 2006

Objective:Visible changes to chromosomes structure and morphology play a very important part as an indicators of genetic damage in both clinical and cancer studies. Most of the changes encountered in clinical studies are “secondary” or “derived” aberrations. This is true in cancer studies which is an ongoing production of aberrations, so that in some cells, a mixture of primary and secondary changes are observed and a continuously changing karyotype are seen. The study was undertaken to know the secondary chromosomal rearrangements encountered in hematological malignancies.

Methods:Cytogenetic study was carried out in 698 patients suspected for hematological malignancies from peripheral blood or bone marrow cells. 45 cases were further selected for FISH study by Vysis and in-house probes.

Results:Out of 698 cases referred, 53 [7.6%] cases were found to have secondary chromosomal rearrangements along with primary chromosomal alterations. The pattern of abnormalities varies greatly between malignancies, ranging from simple balanced rearrangements to complex abnormalities affecting both chromosome structure and number. Clonal evolution due to unbalanced karyotype resulting from the additional numerical or structural chromosomal abnormalities followed by gain/ loss of genetic material leads to poor prognosis. However, complex rearrangements involving no loss or gain of the genetic material involve in abnormal clonal evolution may have better prognostication than those with unbalance karyotypic changes. This study demonstrate that primary conventional cytogenetic investigation provides the knowledge and information about the known/unknown chromosomal rearrangements, which are likely to be missed if analysis is based on targeted clonal sequences.