Imatinib was the first BCR-ABL tyrosine kinase inhibitor to become clinically 
available. In this study, we retrospectively evaluated the long-term efficacy of 
low-dose imatinib (final maintenance dose <300 mg per day) due to intolerance, 
in comparison to optimal-dose imatinib (≥300 mg per day) in patients with 
Philadelphia chromosome-positive chronic myeloid leukemia in the chronic phase. 
The Kaplan-Meier estimates of the median time to complete cytogenetic response, 
major molecular response, and complete molecular response were longer for 31 
patients receiving low-dose imatinib (360, 1360, and 1420 days, respectively) 
than 74 patients receiving optimal-dose imatinib (170, 420, and 720 days, 
respectively). However, the differences in response shrank over time and 
progression-free survival were comparable between the two groups. These findings 
suggest that long-term treatment with low-dose imatinib is an acceptable 
alternative for patients with intolerance to the optimal dose.