Efficacy of Dasatinib in a Very Elderly CML Patient Expressing a Rare E13a3 Bcr-Abl1 Fusion Transcript: A Case Report

We report the case of an 89-year-old male diagnosed with chronic-phase CML and expressing a rare e13a3 BCR-ABL1 fusion transcript. His cytogenetic analysis showed the t(9;22) translocation generating the Philadelphia chromosome (Ph), with a multiplex RT-PCR detecting an atypical fragment. Using two primers complementary to exon 10 of BCR and exon 4 of ABL1, a larger PCR product was observed, where after Sanger sequencing, an e13a3 BCR-ABL1 transcript was revealed. Given the diagnosis, the patient received 100 mg of dasatinib every other day and was then monitored by measuring both hematological and cytogenetic parameters, while his BCR-ABL1 transcripts were examined by PCR and semi-nested-PCR. According to the 2013 European Leukemia Network criteria, after six months of dasatinib the patient's response was classified as warning as he displayed 20% of Philadelphia-positive metaphases. Sequencing of the ABL1 catalytic domain did not detect point mutations. A complete cytogenetic response was achieved after one year of dasatinib. However, semi-nested-PCR confirmed the presence of the e13a3 BCR-ABL1 fusion transcript that has persisted up to the latest follow-up visit.