ECE2023 Poster Presentations Thyroid (163 abstracts)
68Ga-PSMA-PET vs 18F-FDG-PET in metastatic radio-refractory differentiated thyroid cancers
Alessandra Colapinto 1 , Cristina Basso 1 , Valentina Vicennati 1 , Stefano Fanti 2 , Elena Tabacchi 2 , Arber Golemi 2 , Letizia Calderoni 2 , Luigia Vetrone 2 , Elisa Lodi Rizzini 3 , Margherita Nannini 4 , Dario De Biase 5 , GIovanni Tallini 6 , Uberto Pagotto 1 & Andrea Repaci 7
1IRCCS Azienda Ospedaliero-Universitaria di Bologna, Alma Mater Studiorum University of Bologna, Department of Medical and Surgical Sciences (DIMEC), Division of Endocrinology and Diabetes Prevention and Care, Bologna, Italy; 2IRCCS Azienda Ospedaliero-Universitaria di Bologna, Nuclear Medicine Unit, Bologna, Italy; 3IRCCS Azienda Ospedaliero-Universitaria di Bologna, Radiotherapy Unit, Bologna, Italy; 4IRCCS Azienda Ospedaliero-Universitaria di Bologna, Oncology Unit, Bologna, Italy; 5Alma Mater Studiorum University of Bologna, Department of Pharmacy and Biotechnology (FaBit), Molecular Diagnostic Unit, Bologna, Italy; 6Alma Mater Studiorum University of Bologna, Department of Experimental, Diagnostic and Specialty Medicine, Anatomic Pathology and Molecular Diagnostic Unit, Bologna, Italy; 7IRCCS Azienda Ospedaliera-Universitaria di Bologna, Division of Endocrinology and Diabetes Prevention and Care, Bologna, Italy
Introduction: Although 18F-FDG-PET has found wide application in the management of radio-refractory differentiated thyroid cancers (RAI-R-DTCs), alternative radiotracers, including 68Ga-PSMA have been recently evaluated. Prostate-specific membrane antigen (PSMA) is in fact overexpressed in the microvasculature of several solid malignancies including thyroid cancers.
Aim: To compare the diagnostic performance between 68Ga-PSMA-PET and 18F-FDG-PET in detecting metastasis of RAI-R-DTCs
Materials and Methods: 12 patients with RAI-R-DTCs underwent radiological evaluation between 2020 and 2022: in particular, CT, FDG-PET and PSMA-PET were consecutively performed over a period of no more than 6 months. The ability of FDG-PET and PSMA-PET in detecting metastases previously identified by CT was evaluated. Next, PSMA uptake (SUVmax) was compared with FDG uptake.
Results: In our population, 7 patients showed no pathological uptake, 4 patients had PET-FDG and PET-PSMA positive lesions and 1 patient had exclusively PET-FDG positive metastasis. Compared to patients without any pathological uptake, patients with PET positive lesions received an higher doses of Iodine-131 (100 vs 150 mCi, P-value 0.018) and showed higher thyroglobulin values at ablation (10.2 ng/ml vs 266 ng/ml, p value 0.005). A total of 42 lesions were identified by CT scan: 11 involved the lymph nodes, 17 the lungs, 8 the bones and 2 the liver. Altogether, 9 metastasis were FDG-PET positive (21.4 %), 5 were PSMA-PET positive (11.9%) of which 4 were also FDG-PET positive (9.5%). Therefore, regardless of the tracer used, no differences were found in the rate of metastases detection (9/42 - 21.4% vs 5/42 – 11.9%, P-value 0.24). FDG-PET positive lesions were thus subdivided: 3 in lymph nodes, 1 in lungs e 5 in bones. Only one lymph node metastasis was exclusively PSMA-PET positive, while 2 lymph node lesions and 2 bone metastasis were both FDG and PSMA-PET positive. These latter had similar SUVmax values, regardless of the tracer used and the site of the metastasis (median SUVmax values 6.2 vs 3.8 in the case of lymph node lesions and 4.8 vs 6.3 for bone metastasis with P-value 0.439 in both cases). None of the liver lesions were identified by PET study. Thus, there was no evidence of a different lesion distribution between the two tracers.
Conclusions: Compared to FDG-PET, PSMA-PET seems not to better detect metastasis in RAI-R-DTCs. Further prospective studies with wider populations are necessary to confirm our results.
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Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
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