Cytogenetic and molecular responses in chronic phase chronic myeloid leukaemia patients receiving low dose of imatinib for intolerance to standard dose.

Imatinib mesylate is the gold standard treatment of chronic myeloid leukaemia (CML) and 400 mg/day is considered the standard dose. Although it is generally well tolerated, some patients require temporary drug discontinuation and permanent dose reduction because of haematological or non-haematological toxicities. Whether or not reduced doses are effective as the standard dose in inducing and/or maintaining complete cytogenetic and molecular response is not clear. We report the outcome of 45 CML patients in early (17) and late (28) chronic phase (CP) in whom, within a series of 250 patients treated with imatinib, reduced the dose of the drug after experiencing adverse events. Median time interval between the start of therapy and dose reduction was 58 days, whereas median administered dose was 300 mg/day. At 6 months from reduction, major cytogenetic responses (MCRs) were observed in 67% of patients, with 58% being complete cytogenetic remission (CCR), and complete molecular response (CMR) were obtained in 18% of patients. At 12 months, all patients who had obtained MCR reached CCR: this was significantly higher in low risk patients (87%) versus non-low risk patients (66 and 46%), and in early phase (82%) versus late phase (53.5%). CMR and major molecular response (MMR) were detected in 20 and 22% of patients, respectively. Low dose imatinib appears effective in patients with intolerance to standard dose, even though long-term effects remain to be established.