Head-to-head comparison of 68Ga-DOTATATE PET/CT and 18F-FDG PET/CT in localizing tumors with ectopic adrenocorticotropic hormone secretion: a prospective study

Abstract

Purpose: Localizing the source of ectopic adrenocorticotropic hormone secretion (EAS) is challenging. This study compared the diagnostic value of ⁶⁸Ga-DOTATATE PET/CT and ¹⁸F-FDG PET/CT in tumors with EAS.

Methods: Thirty-six patients with a suspicion of EAS were enrolled to undergo both ⁶⁸Ga-DOTATATE PET/CT and ¹⁸F-FDG PET/CT within 4 weeks for comparison. Twenty-three underwent surgical resection or biopsy. Immunohistochemical staining for SSTR2 and Ki-67 was performed to correlate with ⁶⁸Ga-DOTATATE uptake and ¹⁸F-FDG uptake, respectively.

Results: EAS tumors were observed in 20/23 patients. Among the 20 patients with histologically proven EAS tumors, ⁶⁸Ga-DOTATATE PET/CT correctly identified the tumor in 15 (75.0%), with an SUV_max ranging from 1.4 to 20.7 (6.7 ± 5.5). ¹⁸F-FDG PET/CT correctly identified the tumor in 12 (60.0%) patients, with an SUV_max ranging from 1.8 to 10.0 (4.0 ± 2.1). Moreover, ⁶⁸Ga-DOTATATE PET/CT unmasked the sources of EAS in 6 patients with negative ¹⁸F-FDG uptake, and ¹⁸F-FDG PET/CT unmasked the sources in 3 patients with negative ⁶⁸Ga-DOTATATE uptake, resulting in EAS tumors being identified in 18 (90%) patients by combining ⁶⁸Ga-DOTATATE PET/CT and ¹⁸F-FDG PET/CT.

Conclusions: ⁶⁸Ga-DOTATATE PET/CT and ¹⁸F-FDG PET/CT are complementary in localizing and discriminating the source of EAS. ⁶⁸Ga-DOTATATE PET/CT combined with ¹⁸F-FDG PET/CT had higher detection rate than each alone.

Trial registration: ⁶⁸Ga-DOTATATE PET/CT in Neuroendocrine Tumors (NCT04041882) URL OF REGISTRY: https://clinicaltrials.gov/ct2/show/NCT04041882.

Keywords: 18F-FDG; 68Ga-DOTATATE; Ectopic adrenocorticotropic hormone secretion (EAS); Positron emission tomography/computed tomography (PET/CT).