THU036 68Ga-DOTATOC PET/CT In Localization Of ACTH-producing Pituitary Tumors In Patients With Cushing Disease

Abstract

Abstract Disclosure: K. Kim: None. Localization of adrenocorticotrophic hormone (ACTH) producing pituitary tumors has paramount importance as definitive management mainly involves surgical resection of tumors. High-resolution functional imaging modalities, such as 68Ga-DOTATOC PET/CT, have been recently introduced in clinical practice for the identification of neuroendocrine tumors. In this study, we focused on the performance of 68Ga-DOTATOC PET/CT as a tool for localizing ACTH secreting pituitary tumors compared to pituitary MRI. In a retrospective cohort study, we identified 44 patients with Cushing disease who underwent both 68Ga-DOTATOC PET/CT and pituitary MRI before TSA in Severance Hospital from 2015 to 2019. 30 of 44 patients with pathologically positive ACTH immunoreactivity confirmed under TSA were included in final analysis. We compared the accuracy of the predicted tumor location on 68Ga-DOTATOC PET/CT and MRI based on the tumor location under TSA.Median age was 34(15-68) years and 25 of 30 patients showed detected tumor in 68Ga-DOTATOC PET/CT. Age (25 vs. 51 years), pre-operative ACTH level (62.21 vs. 26.21 pg/ml). pre-operative cortisol level (20.60 vs. 17.90 pg/ml), and tumor size on MRI (7.75 vs. 5.00 mm) were not differ according to the presence or absence of DOTATOC uptake. The sensitivity of 68Ga-DOTATOC PET/CT was comparable to those of MRI (90.9% vs. 100% in microadenomas, 79.0% vs. 94.7% in macroadenomas, all p >0.05). However, it was inferior to lateralize pituitary adenoma compared to MRI (72.0% vs. 75.9%, p=0.03). The tumors were localized successfully in 18 patients by 68Ga-DOTATOC PET/CT and we divided into two groups depending on successful lateralization. Pre-operative ACTH in successfully lateralized group was significantly higher than that in the failing lateralized group (91.64 vs. 48.54 pg/ml, p=0.010). The area under the curve was measured to be 0.778 with cut-off 96.59pg/ml in ACTH level to determine the successful lateralization. Pre-operative ACTH higher than 96.59 pg/ml showed the best diagnostic accuracy (Sensitivity 50%, specificity 100%).68 Ga-DOTATOC PET/CT showed that successful detection rate was comparable to those of MRI, but success rate of lateralization was inferior. Serum ACTH level determines the successful lateralization of ACTH secreting pituitary tumor in Cushing disease. Presentation: Thursday, June 15, 2023