90Y microsphere treatment of unresectable liver metastases: changes in 18F-FDG uptake and tumour size on PET/CT.
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.
Bienert
Maren
M
Department of Radiology, University of Pittsburgh Medical Center (UPMC), 200 Lothrop Street, Pittsburgh, PA 15213, USA.
McCook
Barry
B
Carr
Brian I
BI
Geller
David A
DA
Sheetz
Mike
M
Tutor
Cecilia
C
Amesur
Nikhil
N
Avril
Norbert
N
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
D015021:Yttrium Radioisotopes; D019788:Fluorodeoxyglucose F18