Oral Presentation 5th International Symposium on Phaeochromocytoma and Paraganglioma 2017

Impact of 123 I-MIBG scintigraphy on clinical decision making in patients with pheochromocytoma and paraganglioma    (#17)

Dipti D Rao 1 , Anouk van Berkel 1 , Ianthe I Piscaer 1 , William F Young 2 , Lucinda L Gruber 2 , Felix F Beuschlein 3 , Ariadni A Spyroglou 3 , Aleksander A Prejbisz 4 , Katarzyna K Hanus 4 , Graeme G Eisenhofer 5 , Massimo M Manelli 6 , Letizia L Canu 6 , Timo T Deutschbein 7 , Martin M Fassnacht 8 , Jacques J.W.M. Lenders 1 5 , Irina I Bancos 2 , Henri H.J.L.M. Timmers 1
  1. Department of Internal Medicine, Division of Endocrinology, Radboud University Medical Center, Nijmegen, The Netherlands
  2. Division of Endocrinology, Diabetes, Metabolism, and Nutrition, Mayo Clinic, Rochester, USA
  3. Medizinische Klinik und Poliklinik IV, Klinikum der Universität München,, Munich, Germany
  4. Department of Hypertension, Institute of Cardiology, Warsaw, Poland
  5. Department of Medicine III and Institute of Clinical Chemistry and Laboratory Medicine, University Hospital Carl Gustav, Technische Universität Dresden, Dresden, Germany
  6. Endocrinology Unit, Department of Experimental and Clinical Biomedical Sciences, University of Florence, Florence, Italy
  7. Department of Endocrinology and Diabetes, University Hospital Würzburg, Würzburg, Germany
  8. Department of Endocrinology and Diabetes, University Hospital Würzburg, Würzburg, Germany

Background: Anatomical imaging with CT or MRI is regarded as first-choice modality for tumour localization in patients with pheochromocytoma and paraganglioma (PPGL). Functional imaging with 123I-labeled metaiodobenzylguanidine (123I-MIBG) is widely used, but the added diagnostic value is unclear. We investigated the impact of 123I-MIBG scintigraphy on diagnosis and treatment of PPGL compared to anatomical imaging alone.

Methods: In this retrospective international multicenter study we evaluated 340 patients with PPGLs (236 unilateral adrenal, 18 bilateral adrenal, 48 extra-adrenal, 12 multifocal, 26 metastatic) from seven centres. All patients underwent both CT and/or MRI and 123I-MIBG scintigraphy. Clinical data were obtained and local imaging reports were analysed centrally by two blinded independent observers. For each patient, tentative diagnoses based on CT/MRI alone, 123I-MIBG alone, CT/MRI plus 123I-MIBG were compared with the actual diagnosis as recorded in registries of the local centers. Results were analysed in relation to tumour location and size, biochemical phenotype, and genotype.

Results: Diagnoses based on only CT/MRI and CT/MRI plus 123I-MIBG showed close concordance with actual diagnoses of 89 and 88.2% respectively (non-significant). In 3 out of 6 patients with false-negative results on CT/MRI, the diagnosis was corrected by 123I-MIBG (1 unilateral, 2 extra-adrenal). In 1 out of 30 patients with false-positive results on CT/MRI, diagnosis was corrected by 123I-MIBG. 123I-MIBG yielded false-positive lesions in 8 patients (7 unilateral, 1 extra-adrenal). Overall, 123I-MIBG resulted in an appropriate change in management for 4 patients (1%) and an inappropriate change for 9 patients (3%) (non-significant).

Conclusion:  The addition of 123I-MIBG scintigraphy to CT/MRI for localization of PPGL does not lead to more correct than incorrect changes in the diagnoses and treatment, even when 123I-MIBG scintigraphy is restricted to patients at risk for metastatic disease. However 123I-MIBG scintigraphy remains necessary for all patients with metastatic PPGL who qualify for 131I-MIBG radiotherapy.