There are different BCR-ABL1 fusion genes that are translated into
proteins that are different from each other, yet all leukemogenic,
causing chronic myeloid leukemia (CML) or acute lymphoblastic leukemia.
Their frequency has never been systematically investigated. In a series
of 45503 newly diagnosed CML patients reported from 45 countries, it was
found that the proportion of e13a2 (also known as b2a2) and of e14a2
(also known as b3a2), including the cases co-expressing e14a2 and el
3a2, was 37.9% and 62.1%, respectively. The proportion of these two
transcripts was correlated with gender, e13a2 being more frequent in
males (39.2%) than in females (36.2%), was correlated with age,
decreasing from 39.6% in children and adolescents down to 31.6% in
patients >= 80 years old, and was not constant worldwide. Other, rare
transcripts were reported in 666/34561 patients (1.93%). The proportion
of rare transcripts was associated with gender (2.27% in females and
1.69% in males) and with age (from 1.79% in children and adolescents
up to 3.84% in patients >= 80 years old). These data show that the
differences in proportion are not by chance. This is important, as the
transcript type is a variable that is suspected to be of prognostic
importance for response to treatment, outcome of treatment, and rate of
treatment-free remission