Cytogenetic follow-up of patients with nonlymphocytic leukemia I. Philadelphia chromosome-positive chronic myeloid leukemia

Chromosomes of blood and bone marrow cells were studied in 53 patients with Philadelphia chromosome (Ph¹)-positive chronic myeloid leukemia (CML). Fifty patients presented with t(9;22) and three with variant translocations: t(17p+;22q?); t(17q+;22q?), and t(1;9;22). Serial studies were carried out in 27 patients during both the chronic and the blastic phase of the disease. Five patients in the chronic phase developed cytogenetic changes in addition to the Ph¹. In two of these cases the changes preceded a transformation into acute leukemia, but in three cases no acceleration of the disease has occurred 1 to 4 years after the emergence of the subclones. Blastic transformation occurred in 15 instances; 11 of these patients acquired additional nonrandom chromosomal changes: trisomy 8 (9 times), i(17q) (4 times), trisomy 17 (2 times), trisomy 19 (7 times), and duplication of the 22q? (6 times). Clonal evolution was found in eight cases, either at the onset of blastic transformation or later in follow-up cultures. The differences between karyotypic evolution during the chronic and blastic phases of CML are discussed, together with their prognostic significance.