The Value of Somatostatin Receptor Imaging with In-111 Octreotide and/or Ga-68 DOTATATE in Localizing Ectopic ACTH Producing Tumors

Abstract

Objective: We aimed to evaluate the value of somatostatin receptor imaging (SRI) with In-111 octreotide and Ga-68 DOTATATE in localizing ectopic ACTH producing tumors.Methods: Nineteen patients who had In-111 octreotide somatostatin receptor scintigraphy (SRS) and/or Ga-68 DOTATATE PET-CT to localize ectopic ACTH producing tumors between the years 2000 and 2012 were included retrospectively in our study. The results of SRI were compared with clinical onset, radiological findings and surgical data of the patients.Results: Sixteen In-111 octreotide SRS and five Ga-68 DOTATATE PET-CT were performed in 19 patients. In eight out of 19 patients, ectopic ACTH secretion site could be detected. In five patients, SRS showed pathologic uptake. In four of these patients, surgery revealed pulmonary carcinoid tumors and in one patient pancreatic neuroendocrine tumor. In one patient, Ga-68 DOTATATE PET-CT revealed pathologic uptake in lung nodule which came out to be pulmonary carcinoid tumor. In another patient who had resection of metastases of atypical carcinoid tumor prior to scans, new metastatic foci were detected both with SRS and Ga-68 DOTATATE PET-CT imaging. In one patient, although SRS was negative, CT which was performed three years later showed a lung nodule diagnosed as pulmonary carcinoid tumor. In 11 patients, ectopic ACTH secretion site could not be detected. In 10 of those patients, scintigraphic and radiological imaging did not show any lesions and in one patient, Ga-68 DOTATATE PET-CT was false positive.Conclusion: SRI has a complementary role with radiological imaging in localizing ectopic ACTH secretion sites. PET-CT imaging with Ga-68 peptide conjugates is a promising new modality for this indication. Conflict of interest:None declared.

PET imaging in ectopic Cushing syndrome: a systematic review

“…There are very few studies comparing PET/CT with PET imaging. In the study of Ozkan et al, one lung neuroendocrine tumor was identified by 68 Ga-DOTATATE PET/ CT which the CT of the thorax could not detect [31]. About the 4 tumors detected by PET as source of ectopic Cushing syndrome in the study by Kakade et al, only two of them were already localized by CT [30].…”

“…Ö zkan et al also demonstrated that 68 Ga-DOTATATE PET/CT could be a promising imaging modality for this indication [31].…”

“…One additional study was found screening the references of the selected articles (8). Finally, 13 articles encompassing 77 patients with ectopic ACTH-secreting tumors who underwent PET imaging were selected for the systematic review [8,15,[27][28][29][30][31][32][33][34][35][36][37] (Fig. 1).…”

A role for 11C-methionine PET imaging in ACTH-dependent Cushing's syndrome

“…Crucially, both techniques depend on tumoral expression of SSTRs (especially SSTR subtypes 2 and 5) and this, coupled with the difficulties inherent in visualising very small lesions, explains why they have found only limited use in CD. Even in EAS there is considerable heterogeneity of SSTR2 and SSTR5 expression with scan sensitivity reported to be of the order of 40-70% (27). 18 F-FDG uptake is linked to tumour glucose metabolism, as opposed to receptor binding, and hence lesions that do not express SSTRs, and are not visualized with octreotide scans, may theoretically be detected with 18 F-FDG-PET (PET/CT) (28).…”

“…The two modalities most commonly used in clinical practice are 111 In-pentetreotide scintigraphy ('octreoscan') and 68 Ga-DOTATATE or 68 Ga-DOTATOC PET/CT. Although both can theoretically be employed to detect ACTH-secreting tumours at any site, it is predominantly in EAS that their role has been established (27). While conventional SSTR scintigraphy lacks spatial resolution (especially for lesions !2 cm), this can be partly overcome through the use of SPECT (singlephoton emission computerised tomography) for image acquisition.…”