Added value of gastrin receptor scintigraphy in comparison to somatostatin receptor scintigraphy in patients with carcinoids and other neuroendocrine tumours

Abstract

Gastrin receptor scintigraphy (GRS) is a new imaging method primarily developed for the detection of metastases of medullary thyroid carcinoma (MTC). As gastrin-binding CCK 2 receptors are also expressed on a variety of other neuroendocrine tumours (NET), we compared GRS to somatostatin receptor scintigraphy (SRS) in patients with NET. SRS and GRS were performed within 21 days in a series of 60 consecutive patients with NET. GRS was directly compared with SRS. If lesions were visible on GRS but not detectable by SRS, other imaging modalities (MRI, CT) and follow-up were used for verification. Of the 60 evaluable patients, 51 had carcinoid tumours, 3 gastrinomas, 2 glucagonomas, 1 insulinoma and 3 paragangliomas. The overall tumour-detection rate was 73.7% for GRS and 82.1% for SRS. In the 11 patients with negative SRS, GRS was positive in 6 (54.5%). Based on the number of tumour sites detected and the degree of uptake, GRS performed better than SRS in 13 patients (21.7%), equivalent images were obtained in 18 cases (30.0%) and SRS performed better in 24 (40.0%) cases. In six of the SRS positive patients, 18 additional sites of tumour involvement could be detected. Overall, GRS detected additional tumour sites in 20% of the patients. Localisation of the primary tumours or their functional status had no influence on the outcome of imaging. GRS should be performed in selected patients as it may provide additional information in patients with NET with equivocal or absent somatostatin uptake.

Indication for Different Mechanisms of Kidney Uptake of Radiolabeled Peptides

“…The aim of our work was primarily to test whether renal accumulation of radiopeptides other than OCT could also be inhibited by GF and by the other known compounds that can reduce renal accumulation of radiopeptides. MG and EX could be considered for PRRT of neuroendocrine tumors as an alternative to OCT if somatostatin receptor expression is low or absent (24,25). However, their high renal uptake would prevent their use for PRRTwith 177 Lu or 90 Y because of the expected renal toxicity limiting the applicable activities.…”

“…In short, ;40 MBq 111 InCl 3 in 100 mL of 0.1 M (MG) or 0.05 M (EX) HCl were added to 100 mL of the peptide dissolved at a concentration of 50 mM in 0. 25 3 were added to the reaction vial containing 100 mg BOM dissolved in 0.25 M ammonium acetate, pH 5.0. After incubation at 80°C for 60 min, quality control was performed using C 18 RP-HPLC as described.…”

Rak rdzeniasty tarczycy — badanie PET/CT ze znakowanymi 68Ga analogami gastryny i somatostatyny

“…The presence of CCK-2 receptors was used for localising MTC and its metastases in different scintigraphic techniques. In some studies, gastrin receptor scintigraphy was used to enhance the sensitivity of SRS, especially in situations where the SRS scans were negative in the presence of advanced MTC or other neuroendocrine tumours [4,5,15]. Gastrin receptor scintigraphy seemed to have higher specificity and positive predictive value, but lower sensitivity than SRS.…”

Peptide-Based Probes for Cancer Imaging

“…The CCK2 ligands used for the first proof of concept were DTPA-linked nonsulfated CCK analogs or a DTPA-d-Glu chelator-modified minigastrin (10). Added value of gastrin receptor scintigraphy with such compounds, compared with somatostatin receptor scintigraphy, could be documented in selected neuroendocrine tumors (11). However, because of inappropriate tumor-to-kidney ratio or occasional low sensitivity, these compounds are not going to be developed further.…”

“…Another bombesin agonist with a novel receptor profile, a panbombesin analog, is characterized by high affinity to all 3 bombesin receptors with possibly broader indications (16). An interesting compound is 99m Tc-demobesin, a tetraamine-derivatized [d-Phe 6 , Leu-NHEt 13 , desMet 14 ] bombesin (6)(7)(8)(9)(10)(11)(12)(13)(14) that turns out to be a full competitive antagonist (17). 99m Tcdemobesin does not internalize significantly into PC-3 tumor cells but is able, nevertheless, to label in vivo GRP-R-expressing PC-3 tumors more intensely and for a longer time than the best available GRP-R agonists (17).…”