Abstract
1715
Objectives Receptor scintigraphy gains more interest for diagnosis and treatment of tumors, in particular for neuroendocrine tumors (NET). BZH3 is a pan-Bombesin analog, which binds to at least 3 receptor subtypes: the BB1 (neuromedin B), BB2 (Gastrin releasing peptide, GRP), and BB3. 68Ga-RGD is a specific tracer for the integrinαVβ3, which plays an important role in angiogenesis and metastatic potential. Purpose of this study was to investigate the kinetics of both tracers in an experimental NET cell line. Furthermore, bombesin kinetics was compared with RGD kinetics.
Methods This study comprised 9 nude rats inoculated with the pancreatic cell line AR42J. Dynamic PET scans using 68Ga-BZH3 and 68Ga-RGD were performed. Standardized uptake values (SUVs) were calculated, and a 2-tissue compartmental learning-machine model (calculation of K1-k4, VB and receptor binding potential (RBP)) as well as a non-compartmental model based on the fractal dimension was used for quantitative analysis of both tracers. Multivariate analysis was used to evaluate the kinetic data.
Results The PET kinetic parameters showed significant differences when individual parameters were compared between groups. Significant differences were found in FD, VB, K1 and INF (p=0.0275, 0.05, 0.05 and 0.0275 respectively). The 56- to 60-min SUV for 68Ga-BZH3 (range of 0.86-1.29 (median, 1.19)) was higher than the corresponding value for 68Ga-RGD (range of 0.78-1.31 (median, 0.99)). Furthermore, FD, VB, K1, and RBP for 68Ga-BZH3 were generally higher than the corresponding values for 68Ga-RGD, whereas k3 was slightly higher for 68Ga-RGD.
Conclusions As a parameter that reflects receptor binding, the increase of K1 for 68Ga-BZH3 indicated higher expression of bombesin receptors than that of αVβ3 (RGD receptors) in neuroendocrine tumours. 68Ga-BZH3 seems better for diagnosis of NETs owing to higher tracer uptake