The Role of Neoadjuvant Imatinib Mesylate Therapy in Sphincter-Preserving Procedures for Anorectal Gastrointestinal Stromal Tumor

Abstract

To explore the role of neoadjuvant imatinib mesylate (IM) therapy in sphincter-preserving procedures for anorectal gastrointestinal stromal tumor (GIST). Between January and December of 2007, 3 patients with primary anorectal GIST who declined recommendations to receive abdominoperineal resection of the rectum, were treated with IM at a single institution. Tumor size, distance to anal edge, and the number of mitoses were compared before and after the treatment. After 12 weeks of IM therapy, conservative surgical procedures were performed. After IM therapy for the 3 patients, computed tomography scan, colonoscopy, and biopsy showed a decrease in size of the rectal mass, an extension in the distance to anal edge, and a reduction in mitotic count. During this treatment regimen, the patients did not experience any side effects. A sphincter-preserving transsacral excision with direct coloanal anastomosis was performed and the resection margins were uninvolved on all sides. During 22 to 28 months postoperatively, the function of anal sphincter was satisfactory and no recurrence occurred among all 3 patients. Neoadjuvant IM therapy for anorectal GIST is safe and effective. Tumor shrinkage and an extension of the distance to anal edge have a clear benefit for the local excision, in terms of feasibility, function preservation, and safety.