Role of imaging in the preoperative staging of small bowel neuroendocrine tumors.

Background: Imaging studies are important in the preoperative staging of patients with small bowel neuroendocrine tumors (NET) and when selecting patients for cytoreduction procedures for metastatic disease. The purpose of this study was to assess the accuracy of preoperative imaging compared with operative findings in the staging of small bowel NET.

Study Design: Sixty-four patients with small bowel NET undergoing laparotomy and who had preoperative imaging with combinations of CT, MR, and radionuclide scintigraphy were reviewed. Results of imaging studies were compared with operative findings to assess the ability of these investigations to detect mesenteric, peritoneal, and hepatic metastases.

Results: Mesenteric nodal metastases were seen on imaging in 47 (73%) patients and were present at laparotomy in 56 (88%) patients. Peritoneal metastases were seen on preoperative imaging in 4 (6%) patients and found at laparotomy in 16 (25%) patients. Hepatic metastases were seen on imaging in 42 patients (66%) and found at laparotomy in 49 (77%). Sensitivity and specificity for detection of hepatic metastases were 77% and 100% for CT, 82% and 100% for MR, 63% and 100% for (123)I-meta-iodobenzylguanadine scintigraphy, and 63% and 100% for (111)In-octreotide. Imaging studies failed to detect hepatic metastases in 7 patients and underestimated the extent of hepatic metastatic disease in 17 patients.

Conclusions: Imaging of small bowel NET, even with combinations of CT, MR, and radionuclide studies, underestimates the extent of peritoneal, mesenteric, and hepatic metastatic disease. Accurate staging of small bowel NET might be best performed at the time of laparotomy.