Effects of the mean daily doses of imatinib during the first year on survival of patients with chronic myeloid leukemia in Japan: a study of the Hokkaido Hematology Study Group.

In this study, we retrospectively analyzed 213 Japanese patients with chronic myeloid leukemia (CML) treated with imatinib mesylate. In 150 evaluable patients, mean daily doses were 400 mg or more in 42 patients, 300-400 mg in 42 patients, 200-300 mg in 44 patients and <200 mg in 22 patients. Complete hematologic response was observed in all the 84 patients treated with mean daily doses of 300 mg or more and complete cytogenetic response was achieved in 94.8% of those patients. In comparison with the effects of 300 mg or more, mean daily doses of 200-300 mg led to less complete cytogenetic response (78.6% vs. 94.8%, P < 0.01), shorter complete cytogenetic remission duration (81.3% vs. 95.6% at 24 months, P = 0.01), and lower overall survival (90.0% vs. 98.8% at 36 months, P = 0.03). This study suggests that the mean daily doses of 300 mg (roughly equivalent to 100,000 mg/yr) or more may improve overall survival and that mean daily doses of imatinib during the first year may be one of the prognostic factors for CML in Japan.