Use of an isotopic somatostatin receptor probe to image gut endocrine tumors
I. M. Modlin, E. Cornelius and G. P. Lawton
Department of Surgery, Yale University School of Medicine, New Haven, Conn, USA.
OBJECTIVES: To evaluate the effectiveness of indium In 111 pentetate
(diethylenetriaminepentaacetic acid [DTPA]-D-Phe-labeled octreotide
scintigraphy in the localization of gastroenteropancreatic neuroendocrine
lesions, and to identify covert lesions, determine multicentricity, define
the distribution of metastases, confirm complete removal of tumor
postoperatively, and evaluate the efficacy of therapeutic embolization.
DESIGN: Unmasked comparison. SETTING: Tertiary care referral center.
PATIENTS: We studied 28 patients over a 12-month period. Biochemical
evidence of a gastroenteropancreatic tumor was present in 13 patients.
Octreoscan 111 was employed in four patients with an ambiguous biochemical
diagnosis of gastroenteropancreatic tumor. Postoperative examination to
document complete tumor removal was undertaken in seven patients. In one
patient, Octreoscan 111 was used to evaluate the efficacy of therapeutic
embolization. INTERVENTION: [111In]DTPA-D-Phe-octreotide scintigraphy. MAIN
OUTCOME MEASURE: Identification of somatostatin receptor-bearing
neuroendocrine tumors. RESULTS: Intravenous administration of
[111In]DTPA-D-Phe-octreotide followed by whole-body gamma camera
scintigraphy resulted in the localization of gastroenteropancreatic
neuroendocrine tumors with 75% sensitivity, 100% specificity, 100% positive
predictive value, 63% negative predictive value, and 82% overall accuracy.
CONCLUSIONS: While Octreoscan 111 has been shown to localize the majority
of amine precursor uptake and decarboxylation system (APUD) cell tumors as
well as various other somatostatin-positive tumors, this technique may also
be useful in a number of other circumstances. These include prediction of
tumors that will respond to octreotide therapy, identification of covert
metastases, intraoperative identification of tumors, and postoperative
surveillance. Use of an alternative isotope may provide a vehicle for the
administration of local therapeutic radiation to tumor cells. The precise
efficacy of Octreoscan 111 in the identification of lesions smaller than 3
cm with low-density somatostatin-2 receptor expression remains to be
determined.
