What Is the Optimal Dose and Schedule for Dasatinib in Chronic Myeloid Leukemia: Two Case Reports and Review of the Literature.

Efficacy and safety of dasatinib in chronic phase (CP) chronic myelogenous leukemia (CML) patients has been well established. Initially approved dose and schedule of 70 mg twice daily has been changed to 100 mg once daily after demonstration of the same efficacy with less toxicity. Some patients require significant dose reductions to enable continued treatment with dasatinib. Even at a dose of 80 mg once daily, several patients may require further dose reductions due to substantial toxicity while maintaining good control of their disease. We report two CP-CML patients achieving and maintaining major molecular responses while on very low doses of dasatinib, ultimately achieving undetectable levels of BCR-ABL fusion transcript in their peripheral blood. Observations of several CP-CML cases responding remarkably well to dasatinib despite very low dose and frequent dose interruptions challenge our current understanding and the accuracy of the data regarding the optimum dose and schedule of this drug. In selected intolerant patients, low-dose dasatinib therapy may be a safe and effective alternative treatment option before a treatment discontinuation or change considered.