Lack of Utility of¹¹¹In-Pentetreotide Scintigraphy in Localizing Ectopic ACTH Producing Tumors: Follow-Up of 18 Patients

Abstract

Octreotide scintigraphy has been advocated as the principal imaging modality for localizing ectopic ACTH-secreting tumors in Cushing's syndrome. To assess its usefulness we reviewed the course of 18 consecutive patients with ectopic ACTH-producing tumor. Imaging included (111)In-pentetreotide scintigraphy, computed tomography (CT), and/or magnetic resonance imaging (MRI). Tumor was detected initially in 7/18 patients, and in 3/18 during follow-up. No ACTH-secreting tumor was detected by octreotide scintigraphy when CT/ MRI were negative. Seventeen of forty octreotide scintigrams were abnormal. CT and/or MRI confirmed tumors in 10, but demonstrated nonendocrine lesions in association with 6 false positive octreotide scintigrams. Hepatic venous sampling for ACTH refuted one lesion detected by octreotide and CT scans. Twenty-three of forty octreotide scintigrams were normal. Of these, 8 were false negative, as CT and/or MRI detected tumor; 10 agreed with negative CT and MRI, and 5 correctly refuted false positive CT and/or MRI scans. Repeated CT/ MR, but not octreotide scintigraphy, led to tumor resection in 2 patients. We conclude that octreotide scintigraphy does not offer greater sensitivity than CT/MRI and that false positive scans are common. Although octreotide scintigraphy may be helpful in selected cases, it is not a significant advance over conventional imaging for ectopic ACTH-secreting tumors.

Cushing’s Syndrome Due to Ectopic Corticotropin Secretion: Twenty Years’ Experience at the National Institutes of Health

“…Patients participated in protocols approved by the Investigational Review Board of the National Institute of Child Health and Human Development and gave written informed consent. Some patients were reported previously in studies focused on diagnosis (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21), presentation (22,23), or treatment (24 -26).…”

The ectopic ACTH syndrome

“…While standard 111 In-octreotide scintigraphy (Octreoscan) may occasionally be useful on its own it generally has not shown a source undetectable on CT and MRI, although it does add supportive functional data [12,13,45]. However, even if the data do not support the superiority of the Octreoscan over CT scanning, as shown in a direct comparison [7,9,45], it has been proved useful to enhance their resolution for findings not seen on first assessment [9,15], and there are isolated cases that report its superiority [46,47]. It has been recently suggested that its performance is useful as complementary modality to CT and MRI in specific cases [15,48,49] and should be considered when other imaging modalities fail to localise the ACTH-secreting tumour [18,49,50].…”

PET imaging in ectopic Cushing syndrome: a systematic review

“…Traditionally somatostatin receptor scintigraphy has been used in addition to CT and MRI for localization of EAS [18,19]. However, the sensitivity ranges from 30 to 50 % with significant false positives [20,21].…”