The E13a2 BCR-ABL Transcript Negatively Affects Sustained Deep Molecular Response and the Achievement of Treatment-free Remission in Patients with Chronic Myeloid Leukemia Who Receive Tyrosine Kinase Inhibitors

Background: Stopping tyrosine kinase inhibitor (TKI) treatment has become a realistic and safe objective for patients who have chronic myeloid leukemia (CML). Both a sustained deep molecular response (sDMR) and the lack of a molecular recurrence after TKI discontinuation are required to reach a durable treatment-free remission (TFR).

Methods: The potential predictive role of BCR-ABL transcripts in attaining an sDMR and a TFR was analyzed in a strictly consecutive, unselected series of 194 patients who were diagnosed and treated with TKIs at the authors' center.

Results: Of 173 fully evaluable patients, 67 (38.7%) had the e13a2 transcript, and 106 (61.3%) had the e14a2 transcript. Complete cytogenetic and major molecular remissions were not affected, whereas the achievement of both a DMR (P = .008) and an sDMR (P = .004) was favored significantly in patients who had the e14a2 transcript. After a median of 68 months, the sDMR rate was 39.6% in those with the e14a2 transcript and 19.4% in those with the e13a2 transcript. In addition to transcript type, both the early achievement of a molecular response and starting treatment with a second-generation TKI positively affected the attainment of an sDMR in multivariate analysis. The use of a second-generation TKI as frontline treatment increased the sDMR rate in both transcript types. However, in patients who had the e13a2 transcript, the probability of attaining an sDMR was 37% after 60 months and did not increase further despite continuing therapy. Among 51 of 60 patients who attained an sDMR after discontinuing TKIs, 24 experienced a molecular relapse, but all regained molecular remission after resuming TKI treatment. Again, transcript type influenced TFR maintenance (P = .005), because only 2 patients (3%) with the e13a2 transcript enjoyed a durable TFR compared with 25 (23.5%) of those with the e14a2 transcript.

Conclusions: The e13a2 transcript hinders the achievement of deep responses and the possibility of stopping TKI treatment in patients with CML.