Ability of Somatostatin Receptor Scintigraphy to Identify Patients with Gastric Carcinoids: A Prospective Study

Gastric carcinoids are of increasing clinical concern because they may develop in hypergastrinemic states, especially with the increased chronic use of potent acid suppressants that can cause hypergastrinemia. However, gastric carcinoids are difficult to diagnose. Somatostatin receptor scintigraphy (SRS) has a high sensitivity and specificity for localizing carcinoids in other locations. The purpose of this study was to determine whether SRS could localize gastric carcinoids. Two groups of patients with Zollinger-Ellison syndrome (ZES) with hypergastrinemia, each having a different increased risk of developing gastric carcinoids, were studied. One hundred sixty-two consecutive patients with ZES were studied prospectively, with 39 having multiple endocrine neoplasia, type 1 (MEN-1) (high increased risk), and 123 not having MEN-1 (low increased risk). Patients were admitted to the hospital initially and then yearly, undergoing SRS with SPECT, upper gastrointestinal endoscopy, and Jumbo Cup biopsies of any gastric abnormalities, as well as random biopsies of the gastric body. Tumor localization studies were also performed. Both the results of the routine SRS interpretation and the results of a masked review, with particular attention to the stomach of high risk MEN-1 patients, were correlated with the gastric biopsy results. Gastric SRS localization was positive in 19 (12%) of 162 patients. Sixteen patients had a gastric carcinoid, and 12 of these patients had SRS localization. The sensitivity of SRS in localizing a gastric carcinoid was 75%, with a specificity of 95%. Positive and negative predictive values were 63% and 97%, respectively. SRS is a noninvasive method that can identify patients with gastric carcinoids with a reasonable sensitivity and a high specificity. SRS should prove useful in the treatment of patients with hypergastrinemic states that have an increased incidence of gastric carcinoids. In patients with MEN-1, one must realize that localization in the upper abdomen on SRS may be caused by a gastric carcinoid and not a pancreatic endocrine tumor.