Value of somatostatin receptor scintigraphy for preoperative localization of carcinoids

Most carcinoid primary tumors are small and do not cause symptoms until complications (e.g. intestinal obstruction) or symptoms and signs of the carcinoid syndrome occur. Therefore in most cases an assessment of the primary tumor and its metastases must be performed. To determine the value of somatostatin receptor scintigraphy (SRS) for localizing carcinoid tumors, we compared the results of SRS with those obtained with computed tomography (CT) and ultrasonography (US) in 22 patients who had not undergone surgery for removal of the primary tumor. We could not find an advantage of SRS over CT and US for detecting the primary lesions. Tumors > 2 cm in diameter were regularly detected using all methods. SRS was not superior to CT or US for the detection of liver metastases. SRS showed the liver metastases in 16 of 18 patients, whereas CT and US detected liver metastases in all patients. For localization of extrahepatic abdominal and extraabdominal metastases (lymph nodes, bone), whole-body SRS showed an advantage over CT and US. We conclude that SRS is not superior to CT or US for localization of primary carcinoid tumors or liver metastases, although it did prove successful for visualizing extrahepatic and extraabdominal tumor spread. Additionally, SRS is useful for identifying receptor-positive metastases that may be treated by somatostatin analogs. Thus SRS should be performed in patients with a known carcinoid tumor, except those with an appendiceal carcinoid measuring < 1 cm in diameter.