The Philadelphia Chromosome and Chronic Myelogenous Leukemia

Sixty of 73 consecutive patients with clinical and laboratory features of chronic myelogenous leukemia had the Philadelphia (Ph1) chromosome abnormality, as revealed by bone marrow and peripheral blood studies of chromosome morphology. The 13 Ph1-negative patients differed from the larger Ph1-positive group by having lower white blood cell and platelet counts and by having a larger proportion of young children under the age of 7. However, the most significant difference was the finding that the Ph1-negative patients responded poorly to chemotherapy and had a median survival of 18 months as compared to 45 months for the Ph1-positive population (P < 0.01). The Ph1 chromosome was observed during all phases of the disease and was unaffected by treatment. In addition to the Ph1 chromosome, aneuploidy, manifested usually by hyperdiploid Ph1-positive cell lines, was present in 20 percent of the patients. In 2 patients, 2 Ph1 chromosomes were seen in the same cell. A single patient with marked aneuploidy had the only chromosome abnormality seen in the 13 Ph1-negative patients.