ABSTRACT Background Imatinib mesylate (IM) is the first‐line treatment for gastrointestinal stromal tumors (GISTs) and significantly improves patient outcomes. However, high inter‐patient variability in imatinib plasma exposure leads to variable drug response. This study aimed to conduct a retrospective study to clearly assess the factors affecting the steady‐state trough concentration (Css) of imatinib in Chinese patients with GIST. Methods This retrospective analysis enrolled Chinese patients diagnosed with GIST who were treated with IM at 400 mg/d and underwent therapeutic drug monitoring. The C SS of IM was analyzed for differences and correlations with body mass index (BMI), age, sex, and creatinine clearance rate (CCr). Results IM Css exhibited wide interpatient variability in this Chinese GIST cohort ( n = 181). In univariate analyses, patients with higher BMI exhibited significantly lower IM C SS values compared to those with normal BMI ( p < 0.05). Similarly, higher CCr values were associated with reduced IM Css ( p < 0.001). Subsequent multiple linear regression analysis, adjusting for age and BMI, confirmed CCr as an independent determinant of imatinib exposure ( p < 0.05). No significant differences were found between female and male patients or between elderly and non‐elderly patients. Conclusion CCr is an independent predictor of reduced imatinib exposure in Chinese patients with GIST. BMI, while correlated with drug concentration in initial analysis, appears to function as a significant clinical correlate whose association is substantially mediated through CCr. This highlights the importance of monitoring drug levels in patients with renal impairment to optimize dosing.
Tang et al. (Thu,) studied this question.