Aims: Imatinib plasma trough levels (IM Cmin) have been reported to have a considerable clinical impact in patients with gastrointestinal stromal tumors (GISTs). We therefore have investigated the factors affecting IM plasma concentration in Chinese GIST patients.
Methods: IM Cmin in 190 patients with GIST who were taking IM were measured.
Results: In patients treated with IM 300 mg/day (n = 16), 400 mg/day (n = 168), and > 400 mg/day (500: n = 1, 600: n = 5), IM Cmin was 1,564.54 ± 596.15, 1,521.26 ± 610.33, and 2,540.31 ± 1,298.14 ng/mL, respectively. Of the 168 patients treated with IM 400 mg/day, IM Cmin was significantly lower in males (1,353.94 ± 492.89 ng/mL) than in females (1,680.79 ± 669.03 ng/mL, p < 0.01), and in patients with gastrectomy (1,439.60 ± 587.66 ng/mL) than those without gastrectomy (1,649.88 ± 620.12 ng/mL) (p = 0.033). High IM Cmin was correlated with low body weight (p = 0.004) and low body surface area (p < 0.001).
Conclusion: IM Cmin at steady state was significantly associated with body weight and body surface area. Monitoring of IM Cmin might be particularly important for the optimal treatment with IM of male patients and those who have undergone gastrectomy.
Keywords: Gastrointestinal stromal tumor; Imatinib; Therapeutic drug monitoring.
© 2019 S. Karger AG, Basel.