Imatinib Mesylate Dose Adjustment Based on Body Surface Area for CML Chronic Phase Patients Intolerant to Standard Dosage

Chronic myelogenous leukemia (CML) chronic phase (CP) patients cannot tolerate a standard dose (400 mg/day) of imatinib mesylate (IM), sometimes needing a reduced dose. This study aimed to find convenient clinical indexes, rather than plasma trough levels of IM, to define the appropriate IM dosage. Methods: Seventy CML CP patients who experienced an IM dose reduction, or a temporary cessation, were enrolled from 2002 to 2010. The IM treatment was resumed and maintained at either ≥ 400 mg in 25 patients (35.7%; group ≥ 400 mg) or at ≤ 300 mg in 45 patients (64.3%; group ≤ 300 mg). The various clinical characteristics of these patients were evaluated. The plasma trough level of IM was monitored in 20 patients from group ≤ 300 mg. Results: Via multivariate analysis, the IM dosage divided by the body surface area (BSA) was an important index, presupposing a complete cytogenetic response at 12 months (CCyR12). Patients with IM/BSA >206.7 mg/m² showed a higher probability of CCyR12 than others. The IM/BSA (221.7 mg/m²) in group ≤ 300 mg was higher than in group ≥ 400 mg (207.6 mg/m² ). The sustained response and survival rate of group ≤ 300 mg was comparable to that of group ≥ 400 mg. The plasma trough level of IM was significantly correlated with the IM/BSA. Conclusion: Our study suggests that IM dose adjustments, based on IM/BSA, could improve the clinical outcomes in CML CP patients.