Background: Conventional imaging techniques do not routinely detect endocrine gastroenteropancreatic tumors preoperatively. The purpose of this study was to determine whether the new technique of somatostatin-receptor scintigraphy would improve the detection rate of these tumors before initial treatment.
Study design: In a prospective study, 55 patients with a recent diagnosis of endocrine gastroenteropancreatic tumors (22 intestinal carcinoids, 17 gastrinomas, 10 nonfunctioning pancreatic tumors, and 6 insulinomas), were examined with somatostatin-receptor scintigraphy, computed tomography, and ultrasonography. Results of the three imaging modalities were compared with findings at surgical exploration.
Results: None of the insulinomas were localized by somatostatin-receptor scintigraphy, but 4 of 6 insulinomas were detected by computed tomography and ultrasonography. Of 17 gastrinomas, 9 were detected by somatostatin-receptor scintigraphy; computed tomography and ultrasonography localized only 7. Metastases from the gastrinoma were localized by somatostatin-receptor scintigraphy in all cases; computed tomography and ultrasonography detected metastases in only 6 of 9 patients. Nonfunctioning tumors could be localized by somatostatin-receptor scintigraphy, computed tomography, and ultrasonography in 4, 7, and 8 of 10 cases, respectively. Detection rate for corresponding metastases was the same for all three imaging techniques. Primary carcinoids were identified by somatostatin-receptor scintigraphy, ultrasonography, and computed tomography in 7, 8, and 11 of 22 cases, respectively. Extra-abdominal metastases were detected by somatostatin-receptor scintigraphy in only 7 of 19 patients.
Conclusions: In patients with insulinomas, somatostatin-receptor scintigraphy is not indicated because none of the six tumors was imaged. This holds true for nonfunctional pancreatic endocrine tumors and their metastases because no advantage for somatostatin-receptor scintigraphy was found over computed tomography and ultrasonography. In contrast, somatostatin-receptor scintigraphy is superior to computed tomography and ultrasonography for determining the extent of the disease in patients with gastrinomas or carcinoids. The problem of detecting primary tumors in these patients is not solved by somatostatin-receptor scintigraphy.