Positron emitting radiopharmaceuticals including fluorine-18 fluorodeoxyglucose (<sup>18</sup>F-FDG), fluorine-18 dihydroxyphenylalanine (<sup>18</sup>F-FDOPA) and somatostatin analogues labelled with gallium-68 (<sup>68</sup>Ga-SSA) tracks different metabolic pathways or receptor expression/functioning, and proved to be useful in detecting MTC recurrences/metastasis.
A total of 43 somatostatin receptor-positive metastatic MTC patients, treated with <sup>177</sup> Lu-DOTATATE PRRT in a large tertiary care center, were included in this analysis.
Evaluate the efficacy of 68Ga PET/CT in detecting MTC lesions and evaluate tumor expression of somatostatin receptors (SSTRs) associated with 68Ga PET/CT findings.
The value of Ga-DOTATATE in medullary thyroid cancer is being investigated and is currently recommended for use when treatment with somatostatin analogs is an option.
Advances in molecular imaging have led to the development of newer tracers like 18F-TFB (18F-tetrafluoroborate) that are transported through the sodium-iodide symporter (NIS) as well as 68 Ga-DOTATATE that image the somatostatin receptors sub-type 2 expressed in medullary thyroid cancer and some DTC.
The present study evaluated the occurrence of SSTR subtypes 1, 2, 3 and 5 as well as the possible role that each subtype plays in the clinical evolution of patients with MTC.
Somatostatin (SRIH) analogs are commonly used to treat symptoms in medullary thyroid carcinoma (MTC), that expresses SRIH receptors (SSTR1 to SSTR5), as does the human MTC cell line TT.
In the human MTC cell line TT, expressing all somatostatin (SST) receptor subtypes, cell proliferation decreases with SST and SST receptor subtype 2 (sst(2)), but not sst(5), selective agonist treatment, whereas calcitonin (CT) expression and secretion are reduced by SST, but not by sst(2) and sst(5) agonists.
(1) This first comparison between somatostatin receptor status in vivo and ex vivo in MTC shows a marked positive octreoscan despite absent SSTR 2 expression, and (2) this is the first report of a discrepancy between immunostaining and gene transcription for POMC and CRH.
Recently, it has been found that somatostatin analogs and type I interferon are able to control the neuroendocrine symptoms induced by advanced MTC and that they provide clinical benefit by improving the lifestyle of these patients.
In the present study, we investigated these mechanisms in human thyroid medullary carcinoma (TT) cells, which exhibit only inhibition of SS mRNA with DEX.