Safety of Imatinib Mesylate in a Multicenter Expanded Access Program in Adult Patients with Gastrointestinal Stromal Tumors in the Adjuvant Setting

Background: Gastrointestinal stromal tumors (GISTs) are mesenchymal tumors most often caused by activating mutations of the KIT gene. KIT tyrosine kinase inhibitors provide targeted therapy for the underlying genetic mutation, and adjuvant therapy is indicated for patients who are at significant risk of relapse following GIST resection. This is a report of the safety of imatinib in patients with GIST in the adjuvant setting in an expanded access program. Methods: In this multicenter, open-label, single-arm trial, safety was assessed based on the frequency of adverse events (AEs). Results: Three hundred patients were treated and analyzed; 40 patients discontinued treatment. Median overall exposure during the program was 181 days (range 9-420); most patients (260/300 treated) completed the study. Six patients had disease recurrence, 4 of whom discontinued. In line with previously published reports, the most frequent AEs were nausea, diarrhea, and periorbital edema. The AEs were mild to moderate in most cases (76%). Conclusions: These findings are in agreement with the known safety profile of imatinib and confirm the safety of imatinib at 400 mg/day in the adjuvant setting. The incidence of severe AEs was low.