title: Determination of Radiation Absorbed Dose to Primary Liver Tumors and Normal Liver Tissue Using Post-Radioembolization (90)Y PET.
abstract: BACKGROUND
  Radioembolization with Yttrium-90 ((90) Y) microspheres is becoming a more widely used transcatheter treatment for unresectable hepatocellular carcinoma (HCC). Using post-treatment (90) Y positron emission tomography/computerized tomography (PET/CT) scans, the distribution of microspheres within the liver can be determined and quantitatively assessed. We studied the radiation dose of (90) Y delivered to liver and treated tumors.
  
  
  METHODS
  This retrospective study of 56 patients with HCC, including analysis of 98 liver tumors, measured and correlated the dose of radiation delivered to liver tumors and normal liver tissue using glass microspheres (TheraSpheres(®)) to the frequency of complications with modified response evaluation criteria in solid tumors (mRECIST). (90) Y PET/CT and triphasic liver CT scans were used to contour treated tumor and normal liver regions and determine their respective activity concentrations. An absorbed dose factor was used to convert the measured activity concentration (Bq/mL) to an absorbed dose (Gy).
  
  
  RESULTS
  The 98 studied tumors received a mean dose of 169 Gy (mode 90-120 Gy; range 0-570 Gy). Tumor response by mRECIST criteria was performed for 48 tumors that had follow-up scans. There were 21 responders (mean dose 215 Gy) and 27 non-responders (mean dose 167 Gy). The association between mean tumor absorbed dose and response suggests a trend but did not reach statistical significance (p = 0.099). Normal liver tissue received a mean dose of 67 Gy (mode 60-70 Gy; range 10-120 Gy). There was a statistically significant association between absorbed dose to normal liver and the presence of two or more severe complications (p = 0.036).
  
  
  CONCLUSIONS
  Our cohort of patients showed a possible dose-response trend for the tumors. Collateral dose to normal liver is non-trivial and can have clinical implications. These methods help us understand whether patient adverse events, treatment success, or treatment failure can be attributed to the dose that the tumor or normal liver received.
authors.affiliation: Department of Nuclear Medicine, Cleveland Clinic , Cleveland, OH , USA.
authors.forename: Shyam M
authors.initials: SM
authors.lastname: Srinivas
authors.affiliation: Case Western Reserve University School of Medicine , Cleveland, OH , USA.
authors.forename: Navin
authors.initials: N
authors.lastname: Natarajan
authors.affiliation: Ohio University Heritage College of Osteopathic Medicine , Athens, OH , USA.
authors.forename: Joshua
authors.initials: J
authors.lastname: Kuroiwa
authors.affiliation: Ohio University Heritage College of Osteopathic Medicine , Athens, OH , USA.
authors.forename: Sean
authors.initials: S
authors.lastname: Gallagher
authors.affiliation: Department of Nuclear Medicine, Cleveland Clinic , Cleveland, OH , USA.
authors.forename: Elie
authors.initials: E
authors.lastname: Nasr
authors.affiliation: Department of Nuclear Medicine, Cleveland Clinic , Cleveland, OH , USA.
authors.forename: Shetal N
authors.initials: SN
authors.lastname: Shah
authors.affiliation: Department of Nuclear Medicine, Cleveland Clinic , Cleveland, OH , USA.
authors.forename: Frank P
authors.initials: FP
authors.lastname: DiFilippo
authors.affiliation: Department of Quantitative Health Sciences, Cleveland Clinic , Cleveland, OH , USA.
authors.forename: Nancy
authors.initials: N
authors.lastname: Obuchowski
authors.affiliation: Section of Vascular and Interventional Radiology, Cleveland Clinic , Cleveland, OH , USA.
authors.forename: Bana
authors.initials: B
authors.lastname: Bazerbashi
authors.affiliation: Department of Radiation Oncology, Cleveland Clinic , Cleveland, OH , USA.
authors.forename: Naichang
authors.initials: N
authors.lastname: Yu
authors.affiliation: Section of Vascular and Interventional Radiology, Cleveland Clinic , Cleveland, OH , USA.
authors.forename: Gordon
authors.initials: G
authors.lastname: McLennan
keywords: 90 Y PET/CT; HCC; Yttrium-90; dosimetry; radioembolization; response