Potent, transient inhibition of BCR-ABL with dasatinib 100 mg daily achieves rapid and durable cytogenetic responses and high transformation-free survival rates in chronic phase chronic myeloid leukemia patients with resistance, suboptimal response or intolerance to imatinib

Abstract

Background: Dasatinib 100 mg once daily achieves intermittent BCR-ABL kinase inhibition and is approved for chronic-phase chronic myeloid leukemia patients resistant or intolerant to imatinib. To better assess durability of response to and tolerability of dasatinib, data from a 2-year minimum follow-up for a dose-optimization study in chronic-phase chronic myeloid leukemia are reported here.

Design and methods: In a phase 3 study, 670 chronic-phase chronic myeloid leukemia patients with resistance, intolerance, or suboptimal response to imatinib were randomized to dasatinib 100 mg once-daily, 50 mg twice-daily, 140 mg once-daily, or 70 mg twice-daily.

Results: Data from a 2-year minimum follow-up demonstrate that dasatinib 100 mg once daily achieves major cytogenetic response and complete cytogenetic response rates comparable to those in the other treatment arms, and reduces the frequency of key side effects. Comparable 2-year progression-free survival and overall survival rates were observed (80% and 91%, respectively, for 100 mg once daily, and 75%-76% and 88%-94%, respectively, in other arms). Complete cytogenetic responses were achieved rapidly, typically by 6 months. In patients treated with dasatinib 100 mg once daily for 6 months without complete cytogenetic response, the likelihood of achieving such a response by 2 years was 50% for patients who had achieved a partial cytogenetic response, and only 8% or less for patients with minor, minimal, or no cytogenetic response. Less than 3% of patients suffered disease transformation to accelerated or blast phase.

Conclusions: Intermittent kinase inhibition can achieve rapid and durable responses, indistinguishable from those achieved with more continuous inhibition.

Figure 1.

Study CONSORT diagram (adapted from Shah, et al.12). *The reasons 54 of 724 enrolled patients were not randomized or treated were previously reported.^{12 †}165 patients received 100 mg once daily and 1 received 50 mg twice daily. ^‡166 patients were randomized to 50 mg twice daily and 1 was randomized to 100 mg once daily.

Figure 2.

Kaplan-Meier analyses. (A) Duration of complete cytogenetic response. (B) Time to complete cytogenetic response. QD, once daily; BID, twice daily. (C) Progression-free survival (patients who had not died or progressed were censored on the last assessment date). (D) Overall survival (patients lost to follow-up or who had not died were censored on the last date they were known to be alive).