Abstract
BACKGROUND: Adherence to imatinib may be even more limited in the adjuvant setting, as patients receiving adjuvant imatinib often do not experience disease symptoms after tumor removal. This real-world study aimed to gain insight into adherence to imatinib and the effect of adherence on treatment outcomes. METHODS: Postoperative GIST patients who visited the speciality clinic between January 2021 and September 2024 were included in the study. RESULTS: Out of 143 patients, 45 were non-adherent. The restricted mean survival time (RMST) at 3 years was measured for progression-free survival (PFS). Non-adherent patients had an RMST of 24.65 months, whereas adherent patients had an RMST of 32.66 months (P < 0.05). In addition, the plasma trough concentration of imatinib (C(min)) was lower in non-adherent patients than in adherent patients (737.68 vs. 1404.45 ng/mL, P < 0.05). Using therapeutic drug monitoring (TDM) as an objective measurement to assess adherence, C(min) of 1211.50 ng/mL could be the optimal cutoff value to predict the risk of non-adherence. CONCLUSIONS: Poor adherence to imatinib was a notable problem in postoperative adjuvant treatment and appeared to be associated with shorter PFS. Monitoring trough levels gives physicians an objective measurement to assess individual adherence and can support treatment decisions.