The role of 68Ga-DOTA derivatives PET-CT in patients with ectopic ACTH syndrome

Abstract

Introduction and aim Ectopic ACTH secretion (EAS) is mostly secondary to thoracic/abdominal neuroendocrine tumours (NETs) or small cell-lung carcinoma (SCLC). We studied the diagnostic accuracy of CT with 68Ga-Dota derivatives (68Ga-SSTR) PET in localizing ACTH-secreting tumor in patients with EAS. Materials and methods 68Ga-SSTR-PET/CT was performed and compared with the nearest enhanced CT in 18 cases (16 primary and 2 recurrent neoplasms). Unspecific, indeterminate and false-positive uptakes were assessed using conventional imaging, follow-up or histology. Results We diagnosed 13 thoracic (9 primary and 2 recurrent bronchial carcinoids, 2 SCLCs) and 1 abdominal (pancreatic NET) tumors. Eight ACTH-secreting tumors were promptly identified at EAS diagnosis (’overt’, four pulmonary carcinoids with two recurrences and two SCLC); six EAS have been discovered during the subsequent follow-up (’covert’, five bronchial carcinoids and one pancreatic NET). At the time of EAS diagnosis, imaging was able to correctly detect the ACTH-secreting tumour in 8/18 cases (6 new diagnosis and 2 recurrences). During the follow-up, six out of initially ten ‘occult’ cases became ‘covert’. At last available follow-up, CT and 68Ga-SSTR-PET/CT were able to diagnose 11/18 and 12/18 ACTH-secreting tumours, respectively (11/14 and 12/14 considering only overt and covert cases, respectively). Four cases have never been localized by conventional or nuclear imaging (’occult EAS’), despite an average follow-up of 5 years. Conclusion The 68Ga-SSTR-PET/CT is useful in localizing EAS, especially to enhance positive prediction of the suggestive CT lesions and to detect occult neoplasms.

Continuing Challenges in the Definitive Diagnosis of Cushing’s Disease: A Structured Review Focusing on Molecular Imaging and a Proposal for Diagnostic Work-Up

“…18 F-FDG was also found superior to 68 Ga-SSTR imaging in suspected metastasis or in the differentiation between pulmonary infections and ACTHsecreting bronchial tumors in found lung nodules [56,57], while 68 Ga-SSTR appeared superior to 18 F-FDG for de novo ECS tumor detection [51,57]. Conclusions of authors of studies on 68 Ga-SSTR imaging in the tumor detection of ECS were not concordant: while some studies reported high diagnostic accuracy [51,[58][59][60] and found its use helpful in tumor staging and treatment decision making [59][60][61] or even limiting the need for invasive diagnostic procedures [58], others stated that its use should be complementary when conventional imaging is negative or to enhance the positive predictive value of previously found lesions [31,55,[62][63][64]. Dutta et al reported that 68 Ga-DOTA-TOC PET-CT was not useful in the detection of thymic carcinoid, and Varlamov et al suggested that previously reported results on 68 Ga-SSTR imaging for tumor detection in ECS are probably subject to publication bias [65,66].…”

Glucocorticoid Receptor Antagonism Upregulates Somatostatin Receptor Subtype 2 Expression in ACTH-Producing Neuroendocrine Tumors: New Insight Based on the Selective Glucocorticoid Receptor Modulator Relacorilant

“…While increased uptake could also have occurred because of interval increases in the size of the lesions, there was no evidence of a change in tumor size in these patient cases based on CT imaging. SSTR2 is normally expressed in the pituitary gland ( 33 , 34 ), and increased uptake on 68 Ga-DOTATATE scan is seen in eucortisolemic patients. In the patient with an ACTH-secreting metastatic bronchial NET, there was no physiologic uptake of 68 Ga-labeled somatostatin analog in the pituitary gland at baseline.…”

“…68 Ga-DOTATATE imaging of the pituitary showed no uptake at baseline ( Figure 4E ). Normally, the pituitary gland expresses SSTR2, and physiologically increased uptake is seen in eucortisolemic patients’ DOTATATE scans ( 33 , 34 ). During relacorilant treatment, however, the pituitary uptake was restored ( Figure 4E ).…”

X-ray and Radionuclide Imaging in the Diagnosis of ACTH-Producing Neuroendocrine Tumors

“…Напротив, в исследовании Ceccato F. et al [32,39]. Например, в работе Varlamov Е. et al [38] 7 из 9 карциноидных опухолей высокой степени злокачественности хорошо выявлялись при проведении ПЭТ/КТ с соматостатином, меченным галлием-68.…”