Chromosomes in the chronic phase of chronic granulocytic leukemia

Chromosomal analysis of 66 cases with chronic granulocytic leukemia (CGL) was performed using Q- and G-banding techniques. In 65 of the 66 cases, a Philadelphia (Ph 1 ) chromosome with evidence of translocation was observed. Karyotypic abnormalities in addition to the Ph 1 were found in 21 cases. In 6 of these 21 cases, the chronic phase persisted for more than 1 year after the first appearance of these abnormalities; in the remaining 15 cases, the abnormalities appeared shortly before or during the acute phase. Of the 6 cases with karyotypic abnormalities in addition to the Ph 1 in the chronic phase, 3 cases had trisomy #8 and the other 3 cases had a double Ph 1 , a translocation between chromosomes #4 and #9, and loss of the Y chromosome, respectively. In contrast to the 3 cases where trisomy #8 was found in the chronic phase and exhibited no other abnormalities besides the extra #8 and a Ph 1 , all 5 cases whose trisomy #8 was found in the acute phase showed one or more additional chromosomal changes besides the extra #8 and the Ph 1 . In the former 3 cases, the percentage of metaphases with trisomy #8 increased gradually throughout the chronic phase during low dose busulfan therapy. One patient in the chronic phase for more than 14 months had only one extra Ph 1 . In contrast, all of the 7 cases with double Ph 1 chromosomes shortly before or in the acute phase showed one or more additional chromosomes in addition to double Ph 1 . The significance of a double double Ph 1 in the chronic and acute phases appears to be similar to that of trisomy #8 in the respective phases. The observation of trisomy #8 and double Ph 1 might prove to be a useful clinical indicator of the progression of CGL.