Using Multimodal Functional Imaging in the Management of SDHx-Related Pheochromocytoma and Paraganglioma

• Published in: Journal of the Endocrine Society 2021-05, Vol.5 (Supplement_1), p.A1034-A1035
• Main Authors: White, Gemma, Anandappa, Samantha, Masucci, Michael, Hassan, Fahim-Ul, Breen, Louise, Joshi, Mamta, McGowan, Barbara, Hubbard, Jonathan, Obholzer, Rupert, Touska, Philip, Izatt, Louise, Velusamy, Anand, Carroll, Paul
• Format: Article
• Language: English
• Subjects: Tumor Biology
• ISSN: 2472-1972; 2472-1972
• DOI: 10.1210/jendso/bvab048.2117

Background: Succinate Dehydrogenase (SDH) subunit pathogenic variants predispose to Pheochromocytoma and Paraganglioma (PPGL). Functional imaging harnesses the innate receptor expression and the aberrant cellular pathways in PPGLs to improve diagnostic accuracy & guide treatments, including nuclear medicine therapies. Currently commonly available functional imaging modalities include 18F-FDG PET, 123I-MIBG and 68Ga-DOTATATE. Aims: To analyze the use of 123I-MIBG, 18F-FDG PET and 68Ga-DOTATATE in patients harboring SDHB & SDHD pathogenic variants and determine the detection rates for both primary tumors and metastatic sites of disease. Methods: Retrospective review of patient records and imaging reports allowed tumor characteristics and imaging features of 21 patients with SDH-related PPGL to be recorded. Contrast enhanced CT/MRI were used as control to calculate the sensitivity of each functional imaging modality. Avidity of the primary lesion and metastatic deposits were used to calculate detection rates. 123I-MIBG imaging was available for 22 primary tumors (8 SDHB, 14 SDHD), 18FDG-PET for 24 (9 SDHB, 15 SDHD) and 68Ga-DOTATATE for 6 (2 SDHB, 4 SDHD) respectively. Results: 29 PPGLs (primary and metastases, 13 SDHB, 16 SDHD) were identified in 21 patients. 123I-MIBG detected 14/22 (64%) primary tumors; 5/8 (63%) SDHB and 9/14 (64%) SDHD-related PPGL. According to tumor location, 3/3 PCCs, 6/8 HNPGLs and 4/11 non-HNPGLs demonstrated 123I-MIBG avidity. Both18F-FDG PET and 68Ga-DOTATATE detected all PPGLs imaged; 24 (9 SDHB, 15 SDHD) and 6 (2 SDHB, 4 SDHD) respectively, demonstrating 100% sensitivity in the detection of the primary PPGL in all the above locations. 6 metastatic deposits (located in bone, lungs, liver and local lymph nodes) in 4 patients were imaged using all 3 modalities (3 SDHB, 1 SDHD), all of which were avid on 18F-FDG PET and 68Ga-DOTATATE whereas only 50% demonstrated avidity on 123I-MIBG imaging. Discussion: Recent guidelines promote preferential use of 68Ga-DOTATATE and 18F-FDG PET as initial functional imaging modalities in SDHx-related disease over 123I-MIBG. The results from our patient cohort indicate superior sensitivity (100%) for detection of SDHx-related disease with FDG and Dotatate compared with MIBG. In contrast to the current literature, a high proportion (75%) of HNPGLs in our series demonstrated MIBG avidity. Further prospective studies are needed to further evaluate these and various other novel tracers to inform diagnos