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.
Methods: 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.
Results: 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).
Conclusion: 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.