title: 90Y microsphere treatment of unresectable liver metastases: changes in 18F-FDG uptake and tumour size on PET/CT.
abstract: OBJECTIVE
  The intra-arterial administration of 90Y microspheres is a new palliative treatment option for unresectable liver metastases. The aim of this study was to quantitatively assess changes in FDG uptake and tumour size following 90Y microsphere treatment (SIR-Spheres) using 18F-fluorodeoxyglucose (FDG) PET/CT imaging.
  
  
  METHODS
  Five patients with unresectable liver metastases who had failed multiple prior chemotherapy regimens received seven 90Y microsphere treatments to a single liver lobe. All patients underwent a baseline PET/CT scan prior to treatment, as well as up to four follow-up PET/CT scans. The tumour area of 30 liver metastases was measured on CT and the FDG uptake was semiquantitatively assessed by calculation of standardised uptake values (SUVs). A total of 18 FDG-PET/CT scans were performed.
  
  
  RESULTS
  The SUVs in the 30 treated liver metastases decreased from 6.5+/-2.3 at baseline to 4.2+/-1.8 after the first follow-up PET/CT scan (p=0.001). In contrast, the SUVs of untreated metastases increased slightly from 7.2+/-2.3 to 8.0+/-0.8. There was no difference in FDG uptake in treated versus untreated normal liver tissue. Using a previously defined threshold of 20% decrease in SUV from baseline to determine response, 20 out of 30 liver metastases were considered to have responded at the first follow-up PET/CT scan approximately 1 month after treatment. In these metastases, the SUV decreased by 47+/-12%, compared with a slight increase by 5.9+/-19% in ten non-responding metastases (p=0.0001). The changes in tumour size did not correlate with changes in FDG uptake. On the first follow-up PET/CT scan, the tumour area on CT increased by 3.1+/-57% in treated metastases compared with 23.3+/-32% in untreated metastases. A wide range of post-treatment changes of target lesions was observed on CT, including an increase in the size of hypodense lesions, necrotic features and complete resolution of CT abnormalities.
  
  
  CONCLUSIONS
  The metabolic information obtained from FDG-PET/CT seems to provide a more accurate and earlier assessment of therapy response following 90Y microsphere treatment than does the anatomical CT information.
authors.affiliation: Department of Radiology, University of Pittsburgh Medical Center (UPMC), 200 Lothrop Street, Pittsburgh, PA 15213, USA.
authors.forename: Maren
authors.initials: M
authors.lastname: Bienert
authors.forename: Barry
authors.initials: B
authors.lastname: McCook
authors.forename: Brian I
authors.initials: BI
authors.lastname: Carr
authors.forename: David A
authors.initials: DA
authors.lastname: Geller
authors.forename: Mike
authors.initials: M
authors.lastname: Sheetz
authors.forename: Cecilia
authors.initials: C
authors.lastname: Tutor
authors.forename: Nikhil
authors.initials: N
authors.lastname: Amesur
authors.forename: Norbert
authors.initials: N
authors.lastname: Avril
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D019788:Fluorodeoxyglucose F18; D005500:Follow-Up Studies; D006801:Humans; D008099:Liver / Q000473:pathology; D008113:Liver Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000556:secondary; D008297:Male; D008863:Microspheres; D008875:Middle Aged; D009362:Neoplasm Metastasis; D010190:Pancreatic Neoplasms / Q000473:pathology*; D049268:Positron-Emission Tomography / Q000379:methods*; D012189:Retrospective Studies; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome; D015021:Yttrium Radioisotopes
chemical_list: D015021:Yttrium Radioisotopes; D019788:Fluorodeoxyglucose F18