Molecular abnormalities of bcr and c-abl in chronic myelogenous leukemia associated with a long chronic phase.

Median duration of the chronic phase of chronic myelogenous leukemia (CML) is 3 years; less than 20% of patients have a chronic phase greater than 7 years. It is unknown whether the length of chronic phase is stochastic or is predetermined for each patient. Since molecular abnormalities of bcr and c-abl occur in CML, we sought to determine whether there were differences in bcr and c-abl translocation or transcription in individuals with long v short chronic phase. These studies were performed in six patients with CML in whom chronic phase was 7+ to 26 years and 20 patients in whom chronic phase was less than 7 years. All patients had translocation of c-abl to within bcr. The distribution of breakpoints in bcr were similar in both groups. Transcription of the chimeric bcr/c-abl mRNA was comparable. These data suggest that changes in bcr or c-abl alone do not determine the duration of chronic phase in CML; other factors are likely involved.