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Safety and efficacy of dasatinib in patients with advanced gastrointestinal stromal tumors refractory to imatinib and sunitinib: A single arm, multicenters, phase 2 trial.

138 Background: Regorafenib is recommended to treat advanced gastrointestinal stromal tumor (GIST) refractory to imatinib and sunitinib. However, the efficacy is not satisfied, other active agents need to be explored to advanced patients. Methods: In this single arm, multi-center, phase 2 trial, we enrolled patients aged 18 years and older with advanced GIST who had received previous imatinib and sunitinib treatment. Participants were treated with oral dasatinib 50mg twice a day for 2 weeks. If patients were tolerable, then they received dasatinib 70mg twice a day treatment, to tumor progression or intolerable toxicities. The primary endpoint was RECIST-based progression-free survival (PFS) in the intention-to-treat population. The secondary endpoints included response rate, overall survival (OS) and advent events. ctDNA will be analysis in some patients to explore the sensitive biomarker to dasatinib. Results: From May 2016 to June 2018, 58 patients from nine medical centers were enrolled in this study. Two patients had partial response and disease control rate was 62.0%. The median PFS was 3.0 months (95% CI, 2.6-3.4 months). There was no statistic difference of PFS in both subgroup with different primary mutations and in subgroup with different secondary mutations. The patients with wild type GIST had a trend of longer PFS of 5.5 months. In 4 patients with PDGFRA D842V mutation, two patients had stable disease. The median OS was 14.0 months (95% CI, 10.8-17.2 months). The most frequently observed grade 3 adverse events included anemia (10.3%), diarrhea (1.7%). The analysis of ct DNA is ongoing. Conclusions: Dasatinib is an active treatment for patients with GIST who are refractory to imatinib and sunitnib. This study is registered with ClinicalTrials.gov, NCT02776878 . Clinical trial information: NCT02776878.