Therapeutic effects of tyrosine kinase inhibitors and subtypes of BCR-ABL1 transcripts in Japanese chronic myeloid leukemia patients with three-way chromosomal translocations.

We analyzed the clinical responses to thyrosine kinase inhibitors (TKIs) and the molecular and cytogenetic characteristics of 18 chronic myeloid leukemia (CML) patients with 3-way chromosomal translocations. The patients were 14 men and 4 women, aged 23-75 years (median 57 years). The Sokal risk was low in 12 patients, intermediate in 4 patients, and high in 2 patients. Newly identified translocation breakpoints were seen in 7 of the 18 patients. Three patients had the same breakpoints of t(9;22;11)(q34;q11.2;q23). The best responses to TKIs were partial cytogenic response (PCyR) in 2 patients, complete cytogenic response (CCyR) in 3 patients, molecular response (MR) 3.0 in 7 patients, MR 4.0 in 3 patients, and MR 4.5 or higher in 3 patients. A total of 66.7% of patients did not achieve MR 4.0 or higher. In 3 patients in whom TKIs resulted in MR 4.5 or higher for more than 2 years, TKI treatment was discontinued. However, all of them exhibited a loss of MR3.0, at 2, 6, and 20 months after the discontinuation of treatment, respectively, and TKI treatment needed to be restarted. According to Kaplan-Meier survival curve analysis, the overall survival (OS) was 100 months in 56% of the patients. The 60-months cumulative incidences of CCyR, MR3.0, MR4.0 and MR4.5 were 88.9%, 72.2%, 33.3%, and 16.7%, respectively. In the 11 analyzable patients, the BCR-ABL1 mRNA subtype was e14a2 type in 4 patients and e13a2 type in 7 patients.