SPECT Imaging of Neovascularization With 99mTc-3PRGD2 for Evaluating Early Response to Endostar Involved Therapies on Pancreatic Cancer Xenografts in Vivo

Abstract

BackgroundMolecular imaging targeting angiogenesis is warranted for specific monitoring of molecular changes as early therapeutic effects via antiangiogenesis. We explore the predictive value of 99mTc-PEG4-E[PEG4-c(RGDfK)]2 (99mTc-3PRGD2) as an integrin αvβ3 targeting imaging agent for monitoring the efficacy of endostar antiangiogenic therapy and chemotherapy in an animal model, to find a specific pathway that could monitor early therapeutic effects.ResultsTumor growth was significantly lower in treatment groups than in the control group (P<0.05), and also in Endostar + Gemcitabine group than in Endostar group(P=0.034) or Gemcitabine group (P=0.021), and the differences was observed at 28 days after treatment. The difference of uptake of 99mTc-3PRGD2 was observed between the control group and Endostar group(P=0.033) or the combination therapy group(P<0.01) at 7 days after treatment, and at 14 days after treatment between the control group and Gemcitabine group(P<0.01). 99mTc-3PRGD2 accumulation was significantly correlated with microvessel density (r=0.998, P=0.002).ConclusionWith 99mTc-3PRGD2 SPECT, the tumor response to antiangiogenic therapy, chemotherapy, and combination therapy can be assessed at a very early stage of treatment, much earlier than the tumor volume change, which provides new opportunities to develop individualized therapeutic approaches and optimized dosages for effective treatments.