Chromosome changes and splenectomy in Ph-positive CML. III. Predictive parameters in the chronic phase

The karyotype of blastic crisis

The nonrandomness of chromosome clonal evolution in blastic crisis of chronic myeloid leukemia is well established, with three major changes [+8, +Ph, i(17q)] occurring alone or in combination in over 70% of the patients. The chromosome changes observed in different tissues may reveal the origin of the abnormal clones, as well as provide evidence for distinct or common evolution by different cell populations. The significance of the chromosome abnormalities and their relationship to blastic conversion are discussed. In general, chromosome evolution may be considered a rather reliable predictive or diagnostic parameter of blastic crisis but both the nature and the subsequent behavior of abnormal clones appear to be of critical value. As to the clinical/chromosome correlations, a few major points have emerged: the i(17q) aberration is mostly associated with signs of myeloid differentiation of blasts and a marked basophilia; it is mainly observed in the late stage of the disease, but overall median survival of patients with this marker is usually long; more atypical or complex changes usually are associated with a worse prognosis; patients with only a Ph in their blasts may have a longer survival, at least in some cytologic subgroups; and d) the loss of the Y chromosome seems to protect the cell against further clonal evolution. Finally, the relevance of the chromosome changes in the multistage process of blastic conversion is discussed, and the breakpoints of secondary changes recorded so far are reviewed and examined. It appears that certain chromosome regions are more often affected; these might contain genes of critical importance for the final malignant progression. Molecular biology may provide insight, in the future, on the nature and expression of involved genes.

Cytogenetics and cell surface marker analysis in chronic myelocytic leukemia. II. Implications for patient management

Chronic myelocytic leukemia (CML) is a model system for the study of many aspects of malignant disease. One aspect that correlates with decreasing therapeutic response is tumor progression. This progression is often accompanied by clonal evolution. In those cases where aggressive therapy does not prevent this evolution, the clinical response to therapy usually proves to be poor and of short duration. Investigators are concentrating their efforts in three primary, but not mutually exclusive, areas with respect to the clinical management of CML. These include: an attempt to distinguish patients at risk for early transformation from those who will have a prolonged chronic phase; the cryopreservation of autologous bone marrow or buffy coat early in chronic phase for subsequent use in the accelerated phase and; endeavors to identify early markers for disease progression allowing intervention before an irreversible blast crisis occurs. This report deals with two types of potential prognostic markers of transformation: chromosomal and cell surface characteristics. The appearance of nonrandom abnormal chromosomal patterns has been correlated with myeloblastic transformation by many investigators. However, there has always been a subset of CML patients who do not undergo clonal evolution. Additionally, the type(s) of transformation in CML may vary depending on the cell lineages involved. Unlike myeloblastic transformants, many of our patients who do not exhibit clonal evolution as a concomitance of disease progression develop a lymphoblastic transformation. Cytofluorometric analysis can distinguish small populations of abnormal cells with lymphoblastic characteristics (HLA DR+). Initial data suggests that patients expressing the HLA DR+ in their "normal" peripheral blood cells are at risk of undergoing lymphoblastic transformation. The combined use of clinical, cytogenetic, and cytofluorometric data to predict an impending transformation and to discriminate between myeloblastic and lymphoblastic populations allows clinicians to manage their patients more effectively.

Cytogenetic markers in hematoproliferative disorders

In the last decade the improvement of methods of chromosome analysis has allowed new insights into the correlation of specific chromosome changes and certain types of malignant hematologic disorders. Even if a clear-cut correlation between a certain chromosomal marker and a certain malignancy is the exception, it is well established that specific chromosome aberrations occur nonrandomly in specific tumors. Moreover, it has been shown that so-called cellular oncogenes are located on those chromosome regions which are involved in translocations and other structural chromosome abnormalities in particular malignant tumors. The significance of chromosome alterations in leukemias and lymphomas is illustrated by examples concerning well-established data, on the one hand, and findings which have still to be confirmed, on the other. This may demonstrate that human tumor cytogenetics are a dynamically and vigorously developing branch of cancer research.