PET Imaging in Recurrent Medullary Thyroid Carcinoma

Abstract

Purpose. To perform an overview about the role of positron emission tomography (PET) or PET/computed tomography (PET/CT) using different radiopharmaceuticals in recurrent medullary thyroid carcinoma (MTC) based on biochemical findings (increased tumor marker levels after primary surgery). Methods. A comprehensive literature search of studies published in PubMed/MEDLINE, Scopus, and Embase databases through February 2012 regarding PET or PET/CT in patients with recurrent MTC was performed. Results. Twenty-nine studies comprising 714 patients with suspected recurrent MTC were retrieved. Twenty-seven articles evaluated the role of fluorine-18-fluorodeoxyglucose (FDG) PET or PET/CT in recurrent MTC with conflicting results. Diagnostic accuracy of FDG-PET and PET/CT increased in MTC patients with higher calcitonin and carcinoembryonic antigen values, suggesting that these imaging methods could be very useful in patients with more advanced and aggressive disease. Eight articles evaluated the role of fluorine-18-dihydroxyphenylalanine (FDOPA) PET or PET/CT in recurrent MTC reporting promising results. Overall, FDOPA seems to be superior but complementary compared to FDG in detecting recurrent MTC. Few studies evaluating other PET tracers are also discussed. Conclusions. PET radiopharmaceuticals reflect different metabolic pathways in MTC. FDOPA seems to be the most useful PET tracer in detecting recurrent MTC based on rising levels of tumor markers. FDG may complement FDOPA in patients with more aggressive MTC.

The 2015 Revised American Thyroid Association guidelines for the management of medullary thyroid carcinoma: the “evidence-based” refusal to endorse them by EANM due to the “not evidence-based” marginalization of the role of Nuclear Medicine

“…As shown in the literature, the diagnostic performance of FDG-PET/CT improves in patients with recurrent MTC having increased serum calcitonin and CEA levels [9,13]. Also, sensitivity of FDG-PET/CT improves in patients with shorter serum calcitonin and CEA doubling times, confirming the usefulness of this imaging method in patients with more aggressive disease compared to those with comparatively slowly progressive disease [9,13]. In particular, FDG-PET has a relevant prognostic value as it is able to identify MTC patients with poor survival [14,15].…”

“…Furthermore, FDG-PET/CT affected the surgical management of patients with recurrent MTC when lesions were detected [13]. As shown in the literature, the diagnostic performance of FDG-PET/CT improves in patients with recurrent MTC having increased serum calcitonin and CEA levels [9,13]. Also, sensitivity of FDG-PET/CT improves in patients with shorter serum calcitonin and CEA doubling times, confirming the usefulness of this imaging method in patients with more aggressive disease compared to those with comparatively slowly progressive disease [9,13].…”

“…However, a positive F-DOPA-PET/CT might modify the surgical management in a significant number of patients with recurrent MTC [17,18], because this functional imaging method is often performed in patients with recurrent MTC based on rising tumour marker levels after negative conventional morphological imaging studies [16]. Based on the literature, the overall diagnostic performance of F-DOPA-PET/CT in recurrent MTC seems to be higher than that of FDG-PET/CT and improves in patients with higher serum calcitonin levels and shorter serum calcitonin doubling time, reaching a detection rate of 86 % in recurrent MTC with a calcitonin doubling time lower than 24 months [9,16]. A further improvement in the detection rate of F-DOPA-PET/CT in MTC could be achieved by early scan acquisition (around 15 minutes after radiopharmaceutical injection) [19,20].…”

“…Somatostatin receptor PET/CT using somatostatin analogues labelled with gallium-68 is a valuable diagnostic tool for patients with neuroendocrine tumours (NETs) [21,22]. The experience with somatostatin receptor PET/CT in recurrent MTC is limited compared to FDG and F-DOPA [9]. Overall, the diagnostic performance of somatostatin receptor PET/CT in recurrent MTC seems to be inferior compared to other NETs (such as lung and gastroenteropancreatic) due to the variable somatostatin receptor expression in MTC [7,9,11,23].…”

“…In fact, whereas the role of nuclear medicine techniques in preoperative staging of MTC seems limited, on the other hand, an extensive body of evidence in literature clearly supports the role of PET/CT using different radiopharmaceuticals, F-DOPA in particular, in detecting persistent/recurrent MTC [5][6][7][8][9][10][11][12].…”