title: Quantitative Evaluation of Tumor Early Response to a Vascular-Disrupting Agent with Dynamic PET.
abstract: OBJECTIVE
  The purpose of this study is to evaluate the early response of tumors to a vascular-disrupting agent (VDA) VEGF121/recombinant toxin gelonin (rGel) using dynamic [(18)F]FPPRGD2 positron emission tomography (PET) and kinetic parameter estimation.
  
  
  METHODS
  Two tumor xenograft models: U87MG (highly vascularized) and A549 (moderately vascularized), were selected, and both were randomized into treatment and control groups. Sixty-minute dynamic PET scans with [(18)F]FPPRGD2 that targets to integrin αvβ3 were performed at days 0 (baseline), 1, and 3 since VEGF121/rGel treatment started. Dynamic PET-derived binding potential (BPND) and parametric maps were compared with tumor uptake (%ID/g) and the static PET image at 1 h after the tracer administration.
  
  
  RESULTS
  The growth of U87MG tumor was obviously delayed upon VEGF121/rGel treatment. A549 tumor was not responsive to the same treatment. BPND of treated U87MG tumors decreased significantly at day 1 (p < 0.05), and the difference was more significant at day 3 (p < 0.01), compared with the control group. However, the tracer uptake (%ID/g) derived from static images at 1-h time point did not show significant difference between the treated and control tumors until day 3. Little difference in tracer uptake (%ID/g) or BPND was found between treated and control A549 tumors. Considering the tracer retention in tumor and the slower clearance due to damaged tumor vasculature after treatment, BPND representing the actual specific binding portion appears to be more sensitive and accurate than the semiquantitative parameters (such as %ID/g) derived from static images to assess the early response of tumor to VDA treatment.
  
  
  CONCLUSIONS
  Quantitative analysis based on dynamic PET with [(18)F]FPPRGD2 shows advantages in distinguishing effective from ineffective treatment during the course of VEGF121/rGel therapy at early stage and is therefore more sensitive in assessing therapy response than static PET.
authors.affiliation: Center for Advanced Medical Imaging Sciences, Department of Radiology, Massachusetts General Hospital/Harvard Medical School, Boston, MA, 02114, USA.
authors.forename: Ning
authors.initials: N
authors.lastname: Guo
authors.affiliation: Center for Molecular Imaging and Translational Medicine, State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, School of Public Health, Xiamen University, Xiamen, China, 361005.|Laboratory of Molecular Imaging and Nanomedicine, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, 35A Convent Dr, GD937, Bethesda, MD, 20892-3759, USA.
authors.forename: Fan
authors.initials: F
authors.lastname: Zhang
authors.affiliation: Center for Advanced Medical Imaging Sciences, Department of Radiology, Massachusetts General Hospital/Harvard Medical School, Boston, MA, 02114, USA.
authors.forename: Xiaomeng
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Center for Molecular Imaging and Translational Medicine, State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, School of Public Health, Xiamen University, Xiamen, China, 361005.|Laboratory of Molecular Imaging and Nanomedicine, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, 35A Convent Dr, GD937, Bethesda, MD, 20892-3759, USA.
authors.forename: Jinxia
authors.initials: J
authors.lastname: Guo
authors.affiliation: Laboratory of Molecular Imaging and Nanomedicine, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, 35A Convent Dr, GD937, Bethesda, MD, 20892-3759, USA.
authors.forename: Lixin
authors.initials: L
authors.lastname: Lang
authors.affiliation: Laboratory of Molecular Imaging and Nanomedicine, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, 35A Convent Dr, GD937, Bethesda, MD, 20892-3759, USA.
authors.forename: Dale O
authors.initials: DO
authors.lastname: Kiesewetter
authors.affiliation: Laboratory of Molecular Imaging and Nanomedicine, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, 35A Convent Dr, GD937, Bethesda, MD, 20892-3759, USA.
authors.forename: Gang
authors.initials: G
authors.lastname: Niu
authors.affiliation: Center for Advanced Medical Imaging Sciences, Department of Radiology, Massachusetts General Hospital/Harvard Medical School, Boston, MA, 02114, USA. Li.quanzheng@mgh.harvard.edu.
authors.forename: Quanzheng
authors.initials: Q
authors.lastname: Li
authors.affiliation: Laboratory of Molecular Imaging and Nanomedicine, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, 35A Convent Dr, GD937, Bethesda, MD, 20892-3759, USA. shawn.chen@nih.gov.
authors.forename: Xiaoyuan
authors.initials: X
authors.lastname: Chen
mesh_terms: D020533:Angiogenesis Inhibitors / Q000494:pharmacology*; D000818:Animals; D001932:Brain Neoplasms / Q000098:blood supply / Q000378:metabolism / Q000473:pathology*; D045744:Cell Line, Tumor; D005260:Female; D005909:Glioblastoma / Q000098:blood supply / Q000378:metabolism / Q000473:pathology*; D064593:Heterografts; D006801:Humans; D008175:Lung Neoplasms / Q000098:blood supply / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D008819:Mice, Nude; D049268:Positron-Emission Tomography / Q000379:methods*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: D020533:Angiogenesis Inhibitors; D042461:Vascular Endothelial Growth Factor A
keywords: Dynamic PET; Integrin αvβ3; Vascular-disrupting agent; [18F]FPPRGD2