title: 18F-5-fluorouracil dynamic positron emission tomography/computed tomography shows decreased tracer activity after bevacizumab in colorectal metastases.
abstract: OBJECTIVE
  The aim of this study was to evaluate the potential of fluorine-18 (F)-5-fluorouracil (F-5-FU) positron emission tomography/computed tomography (PET/CT) to show differences in 5-FU activity in metastatic colorectal cancer before and after treatment with bevacizumab.
  
  
  METHODS
  This was a pilot study of five patients with newly diagnosed and untreated metastatic colorectal adenocarcinoma. The presence of cancer was confirmed by histopathological analysis before enrollment. Patients underwent F-5-FU PET/CT scanning before treatment and at approximately 24 h postbevacizumab. PET/CT scanning consisted of a dynamic acquisition of images taken 0-20 min after injection of radiotracer. The degree of F-5-FU activity at the metastatic sites was assessed using visual interpretation and semiquantitative standardized uptake value analyses.
  
  
  RESULTS
  The sizes of the metastatic lesions ranged from the smallest lesion measuring 3.04 × 1.50 cm to the largest measuring 4.19 × 2.76 cm. By drawing regions of interest, time-activity curves were generated at each tumor site and area under the curve (AUC) analyses were carried out. At baseline, during the first 5 min after F-5-FU injection the mean AUCtumor/AUCaorta ratio was 1.24 ± 0.30 (range, 0.424-2.14). Less than 24 h after the administration of bevacizumab, the AUCtumor/AUCaorta ratio decreased to 1.06 ± 0.32 (range, 0.23-2.13, P=0.04), which represented an average decline of 20.2% (range, 0.4-45%). Radiotracer uptake on the 5, 10, 15, and 20-min images did not show any significant change between baseline and posttreatment. Follow-up CT imaging showed stable tumor size in one patient and a decrease in metastasis size in the remaining four patients.
  
  
  CONCLUSIONS
  In this pilot study of five patients with metastatic colorectal carcinoma, F-5-FU PET/CT scanning showed a significant perfusion-related decrease in tracer activity 24 h postbevacizumab.
authors.affiliation: Department of Radiology and Molecular Imaging Program at Stanford, Stanford University Medical Center, Stanford, California, USA.
authors.forename: Maurice Henry
authors.initials: MH
authors.lastname: Zissen
authors.forename: Pamela
authors.initials: P
authors.lastname: Kunz
authors.forename: Murugesan
authors.initials: M
authors.lastname: Subbarayan
authors.forename: Frederick T
authors.initials: FT
authors.lastname: Chin
authors.forename: Peter S
authors.initials: PS
authors.lastname: Conti
authors.forename: George A
authors.initials: GA
authors.lastname: Fisher
authors.forename: Andrew
authors.initials: A
authors.lastname: Quon
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D020533:Angiogenesis Inhibitors / Q000008:administration & dosage; D000911:Antibodies, Monoclonal / Q000008:administration & dosage*; D061067:Antibodies, Monoclonal, Humanized; D019540:Area Under Curve; D000068258:Bevacizumab; D015179:Colorectal Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy* / Q000378:metabolism / Q000556:secondary; D005260:Female; D005462:Fluorine Radioisotopes / Q000008:administration & dosage / Q000493:pharmacokinetics; D019788:Fluorodeoxyglucose F18 / Q000008:administration & dosage; D005472:Fluorouracil / Q000008:administration & dosage / Q000493:pharmacokinetics; D006801:Humans; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D014055:Tomography, Emission-Computed / Q000379:methods
chemical_list: D020533:Angiogenesis Inhibitors; D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D005462:Fluorine Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D000068258:Bevacizumab; D005472:Fluorouracil