Clinical characteristics and prognostic significance of chronic myeloid leukemia with rare BCR-ABL1 transcripts.

The prognostic significance of rare BCR-ABL1 transcripts is uncertain in the tyrosine kinase inhibitor (TKI) era. In this retrospective study, 40 (1.7%) patients with rare BCR-ABL1 transcripts were identified from a cohort of 2331 chronic myeloid leukemia (CML) patients; 4 types of rare transcripts were identified, including e1a2 (0.9%), e19a2 (0.4%), e13a3 (0.1%), and e14a3 (0.3%). Compared to patients with the typical transcript, those with the e1a2 transcript had an inferior response to TKIs and a worse outcome. Patients with the e19a2 transcript had a high rate of early optimal response to TKIs, but most of them later lost the complete cytogenetic response (CCyR) due to BCR-ABL1 mutations, resulting in a poor prognosis. Patients with the e13a3/e14a3 transcript responded well to TKIs and had a good outcome. These findings indicate that the type of BCR-ABL1 transcript should be considered when determining the treatment for CML patients in the TKI era.