SPECT improves accuracy of somatostatin receptor scintigraphy in abdominal carcinoid tumors.

Abstract

Abdominal carcinoid tumors are often small and difficult to localize. Somatostatin receptors have been detected in carcinoids, thus enabling their in vivo visualization by scintigraphy with 111In pentetreotide, a radiolabeled somatostatin analog. The aim of this study was to determine the value of 111In-pentetreotide SPECT in the detection of abdominal carcinoids and to compare these results with the outcomes from planar scans and conventional imaging techniques. Eighteen patients with a present, or previously operated, abdominal carcinoid were evaluated. Abdominal SPECT scans were acquired 4 hr postinjection of 111In-pentetreotide and multiple planar views were performed at 4, 24, and 48 hr. No adverse reactions were observed after radiopharmaceutical injection. In 13 of 18 patients, abnormal sites of uptake were found by SPECT, which localized 9 abdominal extrahepatic lesions (in 7 patients) and 33 hepatic lesions (in 10 patients). No pathologic accumulation was seen in the five patients considered in complete remission after surgery. Planar scans visualized 5 abdominal extrahepatic sites (in 4 patients) and 21 liver tumor sites (in 7 patients), while conventional procedures detected 3 abdominal extrahepatic lesions (in 2 patients) and 30 hepatic lesions (in 7 patients). Indium-111-pentetreotide scintigraphy is a safe and practical procedure. SPECT appears to be more sensitive than planar scintigraphy and conventional methods to detect abdominal carcinoids; it can increase the number of visualized tumor sites and that of patients with positive findings and may therefore have a role not only in the mapping of tumor spread but also in therapeutic decisions.