Imatinib Plasma Levels during Successful Long-Term Treatment of Metastatic Gastrointestinal Stromal Tumors

Background/Aims: To investigate whether iimatinib dosage correlated with effective plasma levels and clinical characteristics for Japanese patients undergoing Tong-term (>= 2 years) imatinib therapy for GISTs. Methodology: Twenty-five patients who received imatinib for a metastatic pathologically diagnosed GISTs at our hospital were enrolled. Imatinib response was assessed according to Choi's criteria. Blood samples were collected 22-26 h after the previous imatinib dose before the ext scheduled dose. Results:. Fourteen patients were ale and the median age was 65 years. The median duration of imatinib therapy was 3.8 years (range, 2.0-11.5 years). The median plasma level of imatinib was 1098 k/ml and the minimal plasma level after years of therapy was 789 ng/ml. Imatinib dosage was significantly correlated with-history mum body body surface area of patients who received 400 mg/day imatinib dosage was 1.560 m(2). Conclusions, The minimum level in all patients showing response for years of treatment was 789 ng/ml, suggesting an effective plasma imatinib level of ng/ml. Our results suggest that imatinib 'dosage of 400 mg/day is tecom mended for a patient with a large BSA (>= 1.56 m(2)). an that of 300 mg/day might be sufficient for patients who have undergone a gastrectomy.