The clinical usefulness of chromosome studies in patients with leukemia.

Chromosome banding techniques have revealed the presence of nonrandom chromosome abnormalities in various myeloid leukemias. Of special importance is the association of consistent chromosome translocations with particular types of leukemia; this has long been recognized in CML, which is associated with the Ph1 chromosome, now identified as a 9;22 translocation. We now realize that the 8;21 translocation is seen in at least 10% of patients with AML (M2 marrow), and that the 15;17 translocation is present in at least 40% of patients with APL (M3 marrow). In addition to providing an important technique for more precise classification of myeloid leukemias, cyto-genetic analysis can be used in a general sense to predict possible response to therapy, and thus to predict survival. Although this information is not widely used at present, it may be that physicians would choose supportive therapy rather than aggressive chemotherapy in an individual older than 60 or 70 years of age who had only chromosomally abnormal leukemic cells. On the other hand, a younger patient with a normal karyotype might be identified during the initial therapy as one for whom bone marrow transplantation could be appropriate.