Quantitative functional imaging by Dynamic Contrast Enhanced Ultrasonography (DCE-US) in GIST patients treated with masatinib

Objectives To determine the quantitative parameters of DCE-US for predicting early functional response of patients with metastatic gastrointestinal stromal tumors (GIST). Materials and methods Phase II multicentre clinical trial in patients with metastatic GIST treated with masatinib mesylate (7.5 mg/kg daily by oral route) Patients followed using three different imaging techniques: 1) DCE-US before treatment and on days 1, 7, 15 and after 1, 2, 4, 6 months and every 3 months. 2) CT assessments, using RECIST criteria, before treatment, after 2, 4, 6 months and then every 3 months. 3) FDG PET before treatment and after 1 month. Results Twenty patients included and followed-up for up to 36 months, with 269 DCE-US examinations performed. No significant changes in the 7 selected DCE-US variables on day 1 and 7 vs baseline. On day 15, significant reductions in all the variables related to blood volume recorded: area under the curve (AUC) (p = 0. 004), area under the wash-in (AUWI) (p = 0.002), area under the wash-out (AUWO) (p = 0.002) and Peak Intensity (p = 0.005). Also slope of wash-in changed significantly (p = 0.003). An important reduction in Standard Uptake Values (SUV) recorded in 7/11 patients (PFS > 18 months). Decrease in DCE-US AUC, AUWI and AUWO values on day 7 were predictive of PET-CT results. Conclusions AUC AUWI, AUWO are the DCE-US parameters related to blood volume that at D 15 can predict the response of GISTs to treatment with masatinib. Additional studies are ongoing.