Adherence to the standard dose of imatinib, rather than dose adjustment based on its plasma concentration, is critical to achieve a deep molecular response in patients with chronic myeloid leukemia.

The correlation between imatinib (IM) trough plasma concentration (Cmin) and clinical response was assessed in patients with chronic-phase chronic myeloid leukemia. The Cmin correlated with neither the achievement of complete cytogenetic response (977 vs. 993 ng/ml, P = 0.48) nor a major molecular response (1,044 vs. 818 ng/ml, P = 0.17). Although this was significantly higher in patients with complete molecular response (CMR) than in those without (1,430 vs. 859 ng/ml, P = 0.04), the difference was not significant in the sub-population treated with a standard dose of IM (400 mg/day). Finally, multivariate analysis showed that the IM standard dose, but not Cmin, was predictive of the achievement of CMR. We thus suggest that, in practical clinics at least, adherence to the standard dose is the most important factor for the achievement of CMR.