[Successful Resection of a Giant Rectal Gastrointestinal Stromal Tumor after Neoadjuvant Therapy with Imatinib Mesylate-A Case Report].

A 70-year-old woman was admitted to the hospital with incomplete defecation. Colonoscopy and abdominal computed tomography revealed a submucosal tumor of >50 mm in diameter in the lower rectum. The biopsy specimen was positive for CD34 and c-kit. Based on these findings, the tumor was diagnosed as a gastrointestinal stromal tumor(GIST). We decided to administer neoadjuvant therapy with imatinib mesylate(IM)because we considered that the tumor was too large to remove without tumor perforation. After 28 weeks of administering neoadjuvant therapy, the tumor size was reduced by 40%. Robot-assisted intersphincteric resection and temporary ileostomy were performed without tumor perforation. The patient survived without recurrence for 8 months after the operation, followed by treatment with IM as adjuvant therapy. The present case suggests that neoadjuvant therapy with IM may be useful for locally advanced GIST.