Changes in imatinib plasma trough level during long-term treatment in patients with intermediate- or high-risk gastrointestinal stromal tumors: Relationship between covariates and imatinib plasma trough level

BackgroundImatinib is the first-line adjuvant treatment for gastrointestinal stromal tumors (GISTs). Considering that some studies have suggested that imatinib (IM) plasma trough levels (Cmin) change with time, the aim of this study is to assess the changes in IM Cmin in patients with GIST in a long-term study and to elucidate the relationships between clinicopathological features and IM Cmin.MethodsIn 204 patients with intermediate- or high-risk GIST who were taking IM, IM Cmin was analyzed. Patient data were grouped according to the duration of medication (A: 1–3 months, B: 4–6 months, C: 7–9 months, D: 10–12 months, E: ≤12 months, F: 1236 months). The correlation between IM Cmin at different time stages and clinicopathological characteristics was assessed.ResultsStatistically significant differences were observed between Groups A, C, and D (P = 0.049 and 0.01, respectively). In Group E, IM Cmin correlated with sex (P = 0.049) and age (P = 0.029) and negatively correlated with body weight, height, and body surface area (P = 0.007, 0.002, and 0.001, respectively). In Groups F and G, IM Cmin was significantly higher in non-gastric operation patients than in patients with gastrectomy (P = 0.002, 0.036) and was significantly higher in patients with the primary sites of others than in the stomach (P