Banding in leukemia: Techniques and implications

The presence of the Ph1 chromosome in the hematopoietic cells of individuals with apparent hematologic disorders is virtually diagnostic of CML. In patients without any hematologic or clinical symptoms, the presence of the Ph1 chromosome can be an indicator of the preleukemic state. Published data in cytogenetic studies of acute leukemia hae shown that approximately half the patients exhibit chromosomal abnormalities in their bone marrow. Rowley and Potter reviewed the available banding data for acute nonlymphocytic leukemia and noted that the incidence of chromosomally abnormal patients was underestimated by at least 10-20%. They found various nonrandom chromosome changes including an additional #8 chromosome, the loss of chromosome #7, a gain or loss of #21, frequent structural rearrangements of #8 and 21, and the loss of a sex chromosome. Less banding data are available for acute lymphocytic leukemia. The presence of aneuploid cells in the bone marrow before and/or after treatment did not necessarily indicate a poor prognosis if adequate treatment was given to eradicate the aneuploid cells. In fact, aneuploid cells are useful indicators, the disappearance of which suggests successful treatment leading to long-term survival and possible cure. In contract, the aggressive persistence of aneuploid cells in the bone marrow is a grave prognostic sign. Nowell proposed that a positive marrow chromosome study in nonirradiated patients with preleukemic symptoms suggests that a leukemic phase is imminent, whereas a negative study may indicate a protracted nonleukemic course. Although the new banding techniques appear to be highly useful in cytogenetic studies, relatively little banding data has been accumulated for such leukemia patients. This paucity of banding data is due, at least in part,to a number of technical difficulties encoutered in cytogenetic studies of leukemia patients.