Patterns of recurrence after resection of rectal gastrointestinal stromal tumors and the effect of adjuvant therapy.

Abstract

531 Background: Since gastrointestinal stromal tumors (GISTs) of the rectum are rare, clinical features and treatment outcome have not been well documented. Methods: Data from patients with rectal GIST diagnosed and primarily treated between 2003-2007 at 17 institutions in Japan were collected and analyzed on clinical characteristics, pathologic features and recurrence patterns. Results: Twenty-five patients (11 men and 14 women) with rectal GISTs were collected. Median age was 67years old. Pathological examinations disclosed that the median number of mitoses and the size of tumors were 4 counts/50HPF and 4.5cm, respectively. By the Miettinen criteria, 44 percent (n = 11) were classified as high-risk, 32 percent (n = 8) as low-risk and 16 percent (n = 4) as none-risk gastrointestinal stromal tumors. Sixty-three percent (7/11) of patients with high-risk GISTs had developed recurrence. None of patients (n = 12) with low or none-risk gastrointestinal stromal tumors have recurred after a median follow-up of 1699 (range, 135-3871) days. 85 percent (6/7) of recurrent patients showed loco-regional recurrence. Twelve patients with rectal GISTs received local excision and thirteen patients received extended resection (abdominoperineal resection or low anterior resection). Loco-regional recurrence rate following local excision was 25% (3/12), which was similar with that of extended resection (23%, 3/13).7 patients received neoadjuvant and/or adjuvant imatinib. Only one patient of 7 patients who received perioperative imatinib treatment developed recurrence. Conclusions: Loco-regional recurrence was the most predominant pattern of recurrence after surgical resection of rectal GISTs. The Miettinen criteria were useful to differentiate the high risk group. Recurrence rate was lower in patients treated with perioperative imatinib. Rectal GIST may be optimally managed by perioperative multimodal treatment instead of extending surgical resection.