Successful Treatment with Imatinib Mesylate of a Gastrointestinal Stromal Tumor with c-kit exon 11 Mutation

Gastrointestinal stromal tumors (GISTs) are common form of submucosal tumors of the stomach. Treatment of recurrent GISTs had been unsuccessful because of resistance to chemotherapy and radiotherapy. Recently, GISTs were reported to markedly respond to the molecular target agent, imatinib mesylate. We present here a patient with recurrent GIST and c-kit mutation who was successfully treated with imatinib mesylate. A 66-year-old man underwent partial gastrectomy because of GIST. The tumor was 3 cm in size and positive for KIT expression. One year after the excision, spiral computed tomography (CT) scan revealed four intra-peritoneal recurrence lesions measuring 7, 4, 3 and 2 cm in diameter. One week after the CT scan, we started treatment with imatinib mesylate at 400 mg/day, which resulted within two months in 40% decrease in the sum of the longest diameter. The reduction of tumor size continued for more than 6 months. Analysis of the c-kit mutation of the primary tumor revealed the deletion of 18 bases in exon 11 (codon 551-557), while other exons showed no mutation. In this report, we showed the effectiveness of imatinib mesylate therapy for the recurrence of GIST, especially with c-kit mutation in exon 11