Pathologic complete response with neoadjuvant imatinib for locally advanced pelvic GIST

There are few data that show pathologic complete response (pCR) to imatinib treatment in gastrointestinal stromal tumors (GISTs). We describe a case of a patient with pCR of a pelvic, locally advanced, high-risk GIST who was treated with neoadjuvant imatinib and ultimately underwent a conservative procedure. A 48-year-old male presented with a pelvic mass 10 cm in diameter. Biopsy revealed a gastrointestinal stromal tumor of rectal origin. Although it was considered initially resectable, an extensive procedure would have been necessary for complete resection. Treatment with imatinib was initiated, resulting in partial response. The patient remained on imatinib for over 15 months, maintaining stable disease. Radical prostatectomy with anal sphincter preservation was performed. Pathological report revealed no viable neoplastic cells. The use of imatinib was held for 6 months after the surgery. At a follow-up 15 months after surgery, the patient had no evidence of disease. Our report may help to guide future studies of neoadjuvant imatinib for large pelvic or rectum GISTs that are initially considered unresectable.