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ESMO 2019: Significance of BCR-ABL Transcript Variants in Chronic Phase CML

By: Sarah Campen, PharmD
Posted: Monday, October 14, 2019

In patients with chronic phase chronic myeloid leukemia (CML), the typical BCR-ABL transcript subtypes include two variants: b3a2 and b2a2. A study presented at the European Society for Medical Oncology (ESMO) Congress 2019 in Barcelona (Abstract 1099P) revealed no difference in major molecular response rates between patients with b3a2 and b2a2 transcript types after 1 year of treatment with imatinib. Siva K. Prasad, MD, of Nizam’s Institute of Medical Sciences in Hyderabad, India, and colleagues also found no significant difference in baseline hematologic parameters between patients with the two transcript types.

The study included 140 patients with CML in chronic phase at an institution in India. The b3a2 subtype was seen in 99 patients (71%), and the remaining 41 patients (29%) had the b2a2 subtype. Baseline hematologic parameters, including mean hemoglobin, mean total leukocyte count, and mean platelet count, were similar between the cohorts. Patients with the b2a2 type had a significantly higher European Treatment and Outcome Study (EUTOS) score at presentation.

After 1 year of treatment with imatinib, 63% and 52% of those with the b2a2 and b3a2 subtypes, respectively, achieved a major molecular response (P = .21). Of 17 patients in the b3a2 cohort and 3 patients in the b2a2cohort who were evaluated for kinase domain resistance mutations, 7 in the b3a2 cohort and none in b2a2 cohort had detectable mutations.

Disclosure: The study authors reported no conflicts of interest.

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