Imatinib in c-KIT-mutated metastatic solid tumors: A multicenter trial of Korean Cancer Study Group (UN18-05 Trial).

Introduction: We conducted an open-label, single-arm, multi-center phase II trial to evaluate the efficacy and safety of imatinib chemotherapy-refractory or metastatic solid tumor patients with c-KIT mutations and/or amplification. Methods: c-KIT mutations and amplification were detected using NGS. Imatinib (400 mg daily) was administered continuously in 28-day cycles until disease progression, unacceptable adverse events, or death by any cause. The primary endpoint was the objective response rate (ORR). Result: In total, 18 patients were enrolled on this trial. The most common tumor type was melanoma (n = 15, 83.3%), followed by ovarian cancer, breast cancer, and metastasis of unknown origin (MUO) (each n = 1, 5.5%). The total number of evaluable patients was 17, of which one patient had a complete response, six patients had partial response, and two patients had stable disease. The overall response rate (ORR) of 41.2% (95% CI 17.80-64.60) and a disease control rate of 52.9% (95% CI 29.17-76.63). The median progression-free survival was 2.2 months (95% CI 1.29-3.20), and median overall survival was 9.1 months (95% CI 2.10-16.11). The most common adverse events were edema (31.3%), anorexia (25.0%), nausea (18.8%), and skin rash (18.8%). Conclusion: Imatinib demonstrated modest anti-tumor activity and a manageable safety profile in chemotherapy-refractory solid tumors with c-KIT mutation, especially in melanoma patients. [ABSTRACT FROM AUTHOR]