BCR-ABL1 transcript types showed distinct laboratory characteristics in patients with chronic myeloid leukemia

In chronic myeloid leukemia (CML) two main types of messenger RNA (e14a2 and e13a2) can be produced by BCR-ABL1 gene rearrangement. Due to conflicting results, the clinical value of these transcripts remains controversial. The aim of this study was to identify associations of e14a2 and e13a2 transcripts with laboratory variables and also the response to treatment. This study included 203 adult patients with CML treated with Imatinib as first-line drug in a reference hematology center in Northeast Brazil. Clinical and laboratory data were obtained after informed consent. Samples were collected for RNA extraction and analyzed by reverse transcription-polymerase chain reaction (PCR), according to the international protocol BIOMED-1. The LeukemiaNet 2013 criteria were used to establish the molecular response. The frequency distribution of the BCR-ABL1 transcripts was e14a2 (64%), e13a2 (34%), and double positives (2%). The results showed a statistically significant association of the e14a2 transcript type with thrombocytosis (P = 0.0005) and the e13a2 with higher leukocyte count (P = 0.0491). In a subgroup of 44 patients, the molecular response to treatment with Imatinib was assessed by quantitative PCR at 3 months (BCR-ABL1 ≤ 10%), 6 months (BCR-ABL1 ≤ 1%), or 12 months (BCR-ABL1 ≤ 0.1%). Although patients with the transcript e14a2 showed higher frequency of good responses than patients with the transcript e13a2, this difference was not statistically significant. In agreement with published data, our results showed association of the BCR-ABL1 transcript e14a2 with thrombocytosis and the BCR-ABL1 transcript e13a2 with higher leukocytosis in patients with chronic myeloid leukemia.