PET imaging of inflammation and adenocarcinoma xenografts using vascular adhesion protein 1 targeting peptide 68Ga-DOTAVAP-P1: comparison with 18F-FDG

Purpose The aim of this study was to evaluate inflammation and tumour imaging with a vascular adhesion protein 1 (VAP-1) targeting peptide 68 Ga-DOTAVAP-P1 in comparison with 18 F-FDG. Methods Rats with both subcutaneous human pancreatic adenocarcinoma xenografts and turpentine oil-induced acute sterile inflammation were evaluated by dynamic positron emission tomography (PET) and by digital autoradiography of tissue cryosections. Subsequently, the autoradiographs were combined with histological and immunohistological analysis of the sections. Results 68 Ga-DOTAVAP-P1 delineated acute, sterile inflammation comparable with 18 F-FDG. However, the tumour uptake of 68 Ga-DOTAVAP-P1 was low in contrast to prominent 18 F-FDG uptake. The standardised uptake values of inflammation and tumours by PET were 1.1 ± 0.4 (mean ± SEM) and 0.4 ± 0.1 for 68 Ga-DOTAVAP-P1 and 2.0 ± 0.5 and 1.6 ± 0.8 for 18 F-FDG, respectively. In addition, PET studies showed inflammation to muscle and tumour to muscle ratios of 5.1 ± 3.1 and 1.7 ± 0.3 for 68 Ga-DOTAVAP-P1 and 6.2 ± 0.7 and 4.6 ± 2.2 for 18 F-FDG, respectively. Immunohistochemistry revealed increased expression of luminal VAP-1 on the endothelium at the site of inflammation and low expression in the tumour Conclusion The 68 Ga-DOTAVAP-P1 PET was able to visualise inflammation better than tumour, which was in accordance with the luminal expression of VAP-1 on vasculature in these experimental models.